Device

Abstract

An apparatus comprising: a photonic physically unclonable function (PUF) device for processing an initial optical mode distribution based on a challenge C and outputting a final optical mode distribution, the photonic PUF device comprising a plurality of optical mode waveguides for forming or supporting a plurality of optical modes, for which the initial optical mode distribution is given and from which the final optical mode distribution is generated. A plurality of optical mode mixing layers are arranged to mix a plurality of the optical mode waveguides M. i A plurality of the optical mode waveguides M are spaced apart along the i , which mix the optical modes received by each optical mode mixing layer such that the optical mode distribution exiting each optical mode mixing layer is different from the optical mode distribution received by each optical mode mixing layer. k ) are spaced apart along and coupled to a plurality of said optical mode waveguides and apply a predetermined optical phase shift(s) to vary the phase of each of a plurality of said optical modes such that the subsequent optical modes are mixed into respective optical mode mixing layers (K j ) is received. In an embodiment, for two or more of the plurality of rows of a plurality of optical phase shifters, or for each of the plurality of rows of a plurality of optical phase shifters, a plurality of such optical phase shifters are coupled to each of a plurality of the optical mode waveguides. A security controller controls the photonic PUF device to receive the challenge C and provide a response R. The security controller transforms the challenge C and provides the transformed challenge C to the photonic PUF device, the security controller receives a final optical mode distribution output by the photonic PUF device, and transforms the final optical mode distribution to the response R. A computer readable storage medium includes instructions for a processor to issue challenge C to the security controller and receive response R from the security controller.

Description

Detailed Description of the Invention

[0001] This application claims priority from earlier application No. GB2201275.1, filed February 1, 2022, the contents and elements of which are incorporated herein by reference for all purposes.

[0002] [Field] The present invention relates to a physically unclonable function (PUF) and to a device incorporating a physically unclonable function (PUF).

[0003] 〔background〕 A PUF is a device or process used in applications requiring authentication to improve security against unauthorized access or interference, for example, mobile device-to-mobile device and / or server-to-server authentication processes to authenticate the identity of the mobile device / server. PUFs are distinguished by their ability to be hard to clone, i.e., it is practically impossible to reproduce the device or process that provides the PUF.

[0004] The use of a PUF is characterized by a so-called challenge (C) and response (R) pair (CRP). The PUF is interrogated with a challenge C, for which the PUF outputs a response R. The manufacturer of the PUF will typically collate a large set of CRPs for each PUF. The PUF is then handed over to a third party. When the manufacturer, or a second party with access to the set of CRPs, wants to authenticate the identity of the third party, the third party is requested to interrogate the PUF with a specific challenge C and communicate the response R' from the PUF to the manufacturer / second party. If R' matches the correct R in the manufacturer / second party's possession, the third party authentication is successful.

[0005] Although the described embodiments are in the context of network applications, PUFs can be used in many different applications, for example, they can be used within a single device or computer processor chip, or in generating cryptographic keys.

[0006] A PUF can be understood as an object that provides a physically defined unique identifier or fingerprint when the PUF is interrogated.

[0007] For example, PUFs have been implemented by relying on the power-on state of a battery-powered static random-access memory (SRAM). This state takes the form of a random sequence of logic bits corresponding to each SRAM cell due to inherent manufacturing variations beyond the manufacturer's control. Although the PUF has only a single CRP (i.e., the power-on state of the SRAM cells), the corresponding fingerprint is determined by the physical properties of the device itself, and is not defined by the manufacturer or user. PUFs have been implemented in a variety of forms and technology platforms.

[0008] In summary, the basic properties of a PUF are: a) When challenged, a PUF must provide a response that is unique (with high probability) to that PUF. b) The function that maps challenges to responses relies on the inherent and practically hard-to-clone physical properties of the PUF. c) Knowledge of the manufacturing process used to produce the PUF is not enough to produce or approximate the function exactly.

[0009] PUFs are further characterized by their relative robustness into weak and strong PUFs. A weak PUF is one in which the number of CRPs is small enough that an untrusted party can intercept or otherwise record all possible CRPs. For example, in the case of an SRAM cell, the untrusted party could circumvent the authentication process by recording a single CRP and then impersonating the intended party. A strong PUF is one in which the number of possible CRPs is exponentially large (physical resources such as the number of modes are exponential), or at least large enough that it is practically impossible for an untrusted party to sample a large enough subset to learn the responses to random challenges and thus circumvent the authentication process. Note that this requirement arises because the authentication process can only continue safely if the number of CRPs recorded by the manufacturer / first party has not been exhausted before the PUF is sent to the second / indirect party.

[0010] The present invention seeks to provide an improved PUF and a device incorporating the same.

[0011] BRIEF DESCRIPTION OF THE DRAWINGS According to one aspect of the invention, there is provided an apparatus comprising: A photonic physically unclonable function (PUF) device for processing an initial optical mode distribution based on a challenge C and outputting a final optical mode distribution, the photonic physically unclonable function (PUF) device comprising: Multiple optical modes (e.g., multiple optical modes (M i a plurality of optical modes for forming or supporting a plurality of said optical modes, for which said initial optical mode distribution is provided and from which said final optical mode distribution is generated; A plurality of the optical modes (e.g., a plurality of optical modes (M ia plurality of optical mode mixing layers (K ) spaced apart along a plurality of optical mode waveguides (K ) for forming or supporting a plurality of said optical modes; j ), each optical mode mixing layer (K j ) are received by multiple optical modes (M i ) to mix each optical mode mixing layer (K j ) is the optical mode distribution that exits each optical mode mixing layer (K j ) to make the optical mode distribution different from that received by the optical mode mixing layer (K j )and, A plurality of the optical modes (e.g., a plurality of optical modes (M i a plurality of rows (S) of optical phase shifters spaced along a plurality of optical modes (waveguides for forming or supporting a plurality of optical modes) and coupled to a plurality of said optical modes; k ) by applying a predetermined optical phase shift(s) to generate a plurality of said optical modes (M i ) and the subsequent optical modes are mixed in the respective optical mode mixing layers (K j ) received by a plurality of rows (S k ) and a plurality of said rows (S k ) or a plurality of said rows (S k ), a plurality of the optical phase shifters are arranged to shift a plurality of the optical modes (e.g., a plurality of optical modes (M i a plurality of rows (S) of optical phase shifters coupled to each of the plurality of optical mode waveguides (S) for forming or supporting a plurality of optical mode waveguides (S) k )and, A photonic PUF device, a security controller for controlling the photonic PUF device, receiving the challenge C, and providing a response R, the security controller transforming the challenge C and providing the transformed challenge C to the photonic PUF device, the security controller receiving a final optical mode distribution output by the photonic PUF device, and transforming the final optical mode distribution into the response R; a computer readable storage medium comprising instructions for a processor to issue a challenge C to the security controller and receive a response R from the security controller; An apparatus is provided that includes:

[0012] References to "mode" in the context of "optical mode" herein may be considered to include references to propagating modes of light. Modes may occur in free space, in transparent homogeneous media, in waveguide structures, or in optical resonators. When a light beam propagates, its transverse intensity profile generally changes during propagation. Certain electric field distributions of the wave may be self-consistent during propagation. These are examples of what are known in the art as propagating "modes." The simplest type of propagating mode is a plane wave. In the art, a waveguide structure is generally considered to be a spatially inhomogeneous structure capable of waveguiding. For light propagating in an optical waveguide, the self-consistency of the electric field distribution of the light wave forming a given mode may correspond to the shape of the electric field amplitude profile in the transverse dimension remaining substantially constant at a given position in the waveguide. Light wave modes can be defined by coherence and orthogonality: modes are orthogonal solutions of the electromagnetic wave equations that describe the state of light waves, and they do not interfere (e.g., the optical power of a linear superposition of modes is equal to the sum of the optical powers of the individual modes). Light (photons) within the same mode can be coherent. Waveguides can support multimode optical transmission, in which several different optical propagation modes occur simultaneously.

[0013] References herein to "optical mode distribution" may be considered to include references to distributions of light within an optical mode as well as distributions of light between optical modes. For example, two optical mode distributions may be considered to be different if they correspond to different amplitude distributions across multiple optical modes (e.g., in separate respective optical waveguides) for each distribution. In this sense, a first optical mode distribution may be considered to be "different" from a second optical mode distribution when the first distribution of light (e.g., amplitude) is different from the second distribution of light (i.e., resulting in different amplitude distributions) when distributed among multiple separate optical modes (e.g., separate waveguides).

[0014] According to one aspect of the invention, there is provided an apparatus comprising: A photonic physically unclonable function (PUF) device for processing an initial optical mode distribution based on a challenge C and outputting a final optical mode distribution, the photonic physically unclonable function (PUF) device comprising: Multiple Optical Modes (M i ) (e.g., multiple optical modes (M i ) for forming or supporting a plurality of said optical modes (M i ), the initial optical mode distribution is given, and a number of said optical modes (M i ) from which the final optical mode distribution is generated. i )and, A plurality of the optical modes (e.g., a plurality of optical modes (M i a plurality of optical mode mixing layers (K ) spaced apart along a plurality of optical mode waveguides (K ) for forming or supporting a plurality of said optical modes; j ), each optical mode mixing layer (K j ) are received by multiple optical modes (M i ) to mix each optical mode mixing layer (K j ) is the optical mode distribution that exits each optical mode mixing layer (K j ) to make the optical mode distribution different from that received by the j ), comprising a plurality of said optical mode mixing layers (K j ) or more of said optical mode mixing layers (K j ) each of a plurality of said optical modes (M i ) by mixing three or more of the optical mode mixing layers (K j )and, A plurality of the optical modes (e.g., a plurality of optical modes (M i a plurality of rows (S) of optical phase shifters spaced along a plurality of optical modes (waveguides for forming or supporting a plurality of optical modes) and coupled to a plurality of said optical modes; k) by applying a predetermined optical phase shift(s) to generate a plurality of said optical modes (M i ) and the subsequent optical modes are mixed in the respective optical mode mixing layers (K j ) received by a plurality of rows (S k )and, A photonic PUF device, a security controller for controlling the photonic PUF device, receiving the challenge C, and providing a response R, the security controller transforming the challenge C and providing the transformed challenge C to the photonic PUF device, the security controller receiving a final optical mode distribution output by the photonic PUF device, and transforming the final optical mode distribution into the response R; a computer readable storage medium comprising instructions for a processor to issue a challenge C to the security controller and receive a response R from the security controller; An apparatus is provided that includes:

[0015] Optionally or preferably, a plurality of said rows of a plurality of optical phase shifters (S k ) or a plurality of said rows (S k ), a plurality of the optical phase shifters are arranged to shift a plurality of the optical modes (M i ) (e.g., a plurality of optical mode waveguides) and / or a plurality of said optical mode mixing layers (K j ) or more of the optical mode mixing layers (K j ) each of a plurality of said optical modes (M i ) are mixed together.

[0016] Optionally or preferably, the device includes an input portion (e.g., an input component) connectable to a single input optical mode (e.g., connectable to receive, support, or form said single input optical mode) and a plurality of said optical modes (M i and one or more output sections (e.g., output components) connectable to (e.g., connectable to a plurality of said optical mode waveguides), said challenge C including initial optical mode distribution information, said security controller using said initial optical mode distribution information to cause the reconfigurable photonic network to adopt a corresponding configuration for generating said initial optical mode distribution.

[0017] Optionally, or preferably, the reconfigurable photonic network includes a plurality of optical phase shifters (R s ).

[0018] Optionally, or preferably, the reconfigurable photonic network reconfigures light from the single input optical mode into multiple of the optical modes M. i and an array of a plurality of Mach-Zehnder interferometers for converting said initial optical mode distribution into a linear optical state corresponding to said initial optical mode distribution across all required optical modes. The term "linear optical state" may be considered to include a reference to an optical state distributed across all required optical modes. Preferably, any desired initial optical mode distribution may be obtained by converting one optical mode into all of the required optical modes.

[0019] Optionally or preferably, the challenge C includes information for determining an optical phase shifter setting, and the security controller uses this information to determine the optical phase shifter setting to determine the sequence (S k ) and / or a plurality of said optical phase shifters (R s ) to set the

[0020] Optionally or preferably, a plurality of said rows of a plurality of optical phase shifters (S k ) and a plurality of the optical mode mixing layers (K j ) refers to a plurality of the optical modes (M i ) are arranged alternately along the length of the

[0021] Optionally or preferably, j=0 to K, k=0 to K+1 (e.g., K is a positive integer), and the (K+1)th row of the plurality of optical phase shifters (S K+1 ) is used to store a plurality of said optical modes (M i ) for applying said final optical mode distribution adjustment.

[0022] According to one aspect of the present invention, there is provided a photonic physically unclonable function (PUF) device for processing an initial optical mode distribution based on a challenge C and outputting a final optical mode distribution, the device comprising: Multiple Optical Modes (M i ) (e.g., multiple optical modes (M i ) for forming or supporting a plurality of said optical modes (M i ), the initial optical mode distribution is given, and a number of said optical modes (M i ) from which the final optical mode distribution is generated. i )and, A plurality of the optical modes (e.g., a plurality of optical modes (M i a plurality of optical mode mixing layers (K ) spaced apart along a plurality of optical mode waveguides (K ) for forming or supporting a plurality of said optical modes; j ), each optical mode mixing layer (K j ) are received by multiple optical modes (M i ) to mix each optical mode mixing layer (K j ) is the optical mode distribution that exits each optical mode mixing layer (K j) to produce a different optical mode distribution from that received by the j ), comprising a plurality of said optical mode mixing layers (K j ) each of a plurality of said optical modes (M i ) to receive at least a subset of the plurality of optical modes (M i ) for the subset of the amplitudes of the plurality of optical mode mixing layers (K j )and, A plurality of the optical modes (e.g., a plurality of optical modes (M i a plurality of rows (S) of optical phase shifters spaced along a plurality of optical modes (waveguides for forming or supporting a plurality of optical modes) and coupled to a plurality of said optical modes; k ) a plurality of rows (S) of optical phase shifters, which apply a predetermined optical phase shift(s) to change the phase of each of the plurality of optical modes, the optical modes then being received by the respective mixing layers. k )and, a security controller for controlling the photonic PUF device, receiving the challenge C, and providing a response R, the security controller transforming the challenge C and providing the transformed challenge C to the photonic PUF device, the security controller receiving a final optical mode distribution output by the photonic PUF device, and transforming the final optical mode distribution into the response R; a computer readable storage medium comprising instructions for a processor to issue a challenge C to the security controller and receive a response R from the security controller; A photonic physical unclonable function (PUF) device is provided, comprising:

[0023] Optionally, or preferably, a plurality of said optical modes (M i) are formed in each waveguide (eg, optical mode waveguide), and a plurality of the continuous evanescent coupling waveguides correspond to a plurality of regions of a plurality of the waveguides.

[0024] Optionally or preferably, a plurality of said optical mode mixing layers (K j ) each of the plurality of optical modes M i , and generating a plurality of said optical modes (M i ) for said subset of said optical modes (M i ) are formed in each of the waveguides, and the plurality of continuous evanescent coupling waveguides correspond to the plurality of regions of the plurality of waveguides. i ) is a subset of a plurality of said optical modes (M i ) or a plurality of said optical modes (M i ) may be included.

[0025] Optionally, or preferably, for the device or the photonic physical unclonable function (PUF), the spacing of the evanescent coupling waveguides and / or the length over which the evanescent coupling waveguides are in close proximity to each other is determined by the optical mode mixing layer (K j ) is pre-determined such that the strength of the evanescent coupling is determined by a combination of the spacing and the length, as well as microscopic features of a plurality of the waveguides that are not pre-determined (e.g., cannot be pre-determined) during manufacture.

[0026] Optionally or preferably, for the device or the photonic physical unclonable function (PUF), a plurality of the optical mode mixing layers (K j ) at least one of the plurality of optical modes (M i ) or a plurality of said optical modes (M i) to receive all of the plurality of optical modes (M i ) of the at least three or more of the optical modes (M i ) includes a continuous evanescent coupling waveguide that provides mixing of the respective amplitudes for all of the three optical modes (M i ), and / or reference to "at least three" in the context of at least three evanescently coupled waveguides may include, for example: four or more optical modes (M i ), and / or 4 or more evanescently coupled waveguides; 5 or more optical modes (M i ), and / or 5 or more evanescently coupled waveguides; 10 or more optical modes (M i ), and / or 10 or more evanescently coupled waveguides. As mentioned above, the evanescently coupled waveguides may implement mixing of multiple optical modes such that a random walk of photons occurs between multiple optical modes and / or multiple evanescently coupled waveguides. This effect has been found to be significantly enhanced when the number of modes and / or waveguides involved in the mixing process is increased beyond two. The optical modes involved in the mixing process (M i ) and / or the total number "M" of waveguides (i.e., "all of them") may be 3 or more, such as M≧3, or M≧5, or M≧10.

[0027] Optionally, or preferably, the apparatus or photonic physically unclonable function (PUF) of any preceding claim, wherein the initial optical mode distribution includes a light source generated from the light source, which may include a laser (e.g., an electrically pumped integrated laser), an LED light source having a narrow light spectrum, or light in a quantum state (e.g., squeezed light or single photons).

[0028] Optionally or preferably, the device or the photonic physically unclonable function (PUF) comprises a plurality of said optical modes (Mi ) (eg, connected to a plurality of said optical mode waveguides).

[0029] Optionally or preferably, the optical measurement device includes a photodiode or a single photon detector.

[0030] Optionally or preferably, the photonic physically unclonable function (PUF) is an integrated photonic chip.

[0031] Optionally or preferably, the integrated photonic chip is formed from one or more of silicon (Si), silicon nitride (SiN), silica (SiO2), gallium arsenide (GaAs), indium phosphide (InP), polymer, lithium niobate (LiNbO), or aluminum nitride (AlN).

[0032] Optionally or preferably, the apparatus or the photonic physical unclonable function (PUF) comprises a plurality of the optical phase shifters, the plurality of the optical phase shifters being independently controllable and / or the plurality of the optical phase shifters may comprise thermo-optical devices, electro-optical devices, piezoelectric devices, birefringent devices, microelectromechanical devices, strain-induced devices, or acousto-optical devices.

[0033] According to one aspect of the invention, there is provided a photonic physically unclonable function (PUF) device for processing an initial optical mode distribution based on a challenge C and outputting a modified optical mode distribution, the device comprising: Multiple Optical Modes (M i ) (e.g., multiple optical modes (M i ) for forming or supporting a plurality of said optical modes (M i ), the initial optical mode distribution is given, and a number of said optical modes (M i ), from which the modified optical mode distribution is generated.i )and, A plurality of the optical modes (e.g., a plurality of optical modes (M i a plurality of optical mode mixing layers (K ) spaced apart along a plurality of optical mode waveguides (K ) for forming or supporting a plurality of said optical modes; j ), each optical mode mixing layer (K j ) are received by multiple optical modes (M i ) to mix each optical mode mixing layer (K j ) is the optical mode distribution that exits each optical mode mixing layer (K j ) to make the optical mode distribution different from that received by the j )and, A plurality of the optical modes (e.g., a plurality of optical modes (M i a plurality of rows (S) of optical phase shifters spaced along a plurality of optical modes (waveguides for forming or supporting a plurality of optical modes) and coupled to a plurality of said optical modes; k ) by applying a predetermined optical phase shift(s) to generate a plurality of said optical modes (M i ) and the phase of each of the subsequent optical modes (M i ) are the optical mode mixing layers (K j ) received by a plurality of rows (S k )and, a security controller for controlling the photonic PUF device, receiving the challenge C, and providing a response R, the security controller transforming the challenge C and providing the transformed challenge C to the photonic PUF device, the security controller receiving a final optical mode distribution output by the photonic PUF device, and transforming the final optical mode distribution into the response R; Including, The security controller includes: a) the security controller using the challenge C to set an initial optical mode distribution for processing by the PUF; b) the security controller acquiring the amplitude of the modified optical mode distribution; c) the security controller providing the amplitude of the modified optical mode distribution to the PUF device to be processed as a further initial optical mode distribution; d) the security controller repeating steps b) and c) T times to generate the final optical mode distribution; a photonic PUF device configured to operate the photonic PUF device to generate the final modified optical mode distribution by an iterative process including:

[0034] Optionally or preferably, the security controller, as part of step c), k ) of the plurality of optical phase shifters or the plurality of rows (S k ) the settings of all of the optical phase shifters, and the PUF device may be configured to process the further initial optical mode distribution based on the changed settings.

[0035] Optionally, or preferably, the security controller determines a plurality of said strings (S k ) is set using the challenge C.

[0036] Optionally, or preferably, the response R is transformed from the final optical mode distribution only.

[0037] Optionally, or preferably, the response R is transformed from one or more of the modified optical mode distributions obtained in step b), or from all of the modified optical mode distributions obtained in step b).

[0038] Optionally or preferably, the photonic PUF device includes an input (e.g., an input component) connectable to a single input optical mode (e.g., connectable to receive, support, or form the single input optical mode) and a plurality of said optical modes (M i and (one or more) output sections (e.g., output components) connectable to a first input port (e.g., a second output port) and (c) configured to connect to a second input port (e.g., a third output port) and (d) configured to connect to a second input port (e.g., a fourth output port) and (e.g., a fourth output port) and (c) configured to connect to a second input port (e.g., a fourth ...

[0039] Optionally or preferably, step c) includes the security controller using the amplitude of the modified optical mode distribution to cause the reconfigurable photonic network to adopt a corresponding configuration for generating the amplitude of the modified optical mode distribution and providing the amplitude to the PUF device.

[0040] Optionally, or preferably, step c) comprises the security controller transforming the modified optical mode distribution and providing the modified optical mode distribution to the PUF device for processing as a further initial optical mode distribution.

[0041] Optionally or preferably, the security controller uses the transformed modified optical mode distribution to cause the reconfigurable photonic network to adopt a corresponding configuration for generating the transformed modified optical mode distribution and providing the transformed modified optical mode distribution to the PUF device.

[0042] Optionally or preferably, the photonic PUF device measures a plurality of the optical modes (M i ) (eg, connected to a plurality of said optical mode waveguides).

[0043] According to one aspect of the invention, there is provided a method or process for forming (e.g., manufacturing) a system including a photonic Physical Unclonable Function (PUF) device for receiving an initial optical mode distribution (e.g., associated with a challenge C) and outputting a final optical mode distribution (e.g., associated with a response R). Preferably, the system further includes information relating (linking) a plurality of challenges C to a plurality of responses R, respectively. The method comprises: a) Multiple optical modes (M i ) (e.g., multiple optical modes (M i Providing a plurality of optical mode waveguides for forming or supporting a plurality of said optical modes (M i ), the predetermined initial optical mode distribution may be given for a number of said optical modes (M i ), from which the final optical mode distribution can be generated in use; b) a plurality of said optical modes (e.g., a plurality of optical modes (M i a plurality of optical mixing layers (K ) spaced apart along a plurality of optical mode waveguides (K ) for forming or supporting a plurality of said optical modes; j ), each optical mode mixing layer (K j ) are received by multiple optical modes (M i ) to mix each optical mode mixing layer (K j ) is the optical mode distribution that exits each optical mode mixing layer (K j ) different from the optical mode distribution received by the optical mixing layer (K j ) providing a c) a plurality of said optical mixing layers (K j) of the optical mixing layers (K j ) at points before and after the optical mode mixing layer (K j ) coupled to a plurality of said optical modes (e.g., a plurality of optical modes (M i forming a plurality of optical coupling interfaces to a plurality of optical mode waveguides to form or support the plurality of optical mode waveguides; d) (e.g., associating a plurality of challenges C with respective responses R) j performing tomography through a plurality of said optical coupling interfaces to determine the optical mode mixing behavior of said optical coupling interfaces; e) removing the plurality of optical coupling interfaces after step d) is completed; and Includes.

[0044] Optionally, or preferably, the method further comprises: i a plurality of rows (S) of optical phase shifters spaced along a plurality of optical modes (waveguides for forming or supporting a plurality of optical modes) and coupled to a plurality of said optical modes; k ) by applying a predetermined optical phase shift(s) to generate a plurality of said optical modes (M i ) and the phase of each of the subsequent optical modes (M i ) are received by respective optical mode mixing layers. k ), and in step c), the plurality of optical coupling interfaces are provided with a series (S k ) and / or each (subsequent) plurality of optical shifter rows (S k+1 ) is attached to the point before it.

[0045] Optionally or preferably, step d) comprises performing said tomography separately through each optical mode and / or for each optical mode mixing layer separately.

[0046] Optionally or preferably, step d) comprises varying the light input of each optical mode entering each of the optical mode mixing layers and / or the setting of the optical phase shifter during the tomography process and measuring the amplitude of output light from each of the optical mode exiting each of the optical mode mixing layers. The step of determining the mixing behavior in step d) may comprise determining an optical mode unitary transformation that maps an input optical mode distribution to an output optical mode distribution from each of the optical mixing layers.

[0047] The method allows one to determine virtually the complete unitarity for each optical mixing layer. The method is carried out by combining a (characterized) optical mixing layer (Kj) and a series of optical phase shifters (S k ) as a pairwise product with the optical mode (M i ) The method may include a step of parameterizing all unitary operations on the PUF. The method may include a step of determining a function relating all challenges C to their respective responses R. This allows the manufacturer of the PUF to know the function relating all challenges C to their respective responses R, so that the manufacturer can calculate all possible CRPs without probing the PUF. After that, the individual optical mode mixing layers (Kj) are prevented from being optically accessed after manufacture to determine their unitaries, i.e., by physically and permanently modifying the PUF, i.e., the optical coupling interface, which is erased. As a result, access to this information by (unauthorized) third parties is precluded.

[0048] According to one aspect of the present invention, there is provided a method of operating an apparatus or photonic PUF device of any preceding aspect, optionally or preferably comprising using the apparatus or photonic PUF device as part of an authentication process to authenticate a device, a user or communications.

[0049] The optical modes disclosed herein according to any embodiment of the present invention may be formed in each waveguide. j ) supports multiple optical modes (M i ) to provide mixing of the optical modes. In an embodiment according to any aspect of the invention, the continuous evanescent coupling waveguide may correspond to a region of the waveguide in which the optical modes are formed. The evanescent coupling waveguide may implement mixing of the optical modes such that random walk of photons occurs between the optical modes and / or between the evanescent coupling waveguides.

[0050] Depending on the manufacturing technique used to fabricate the waveguide, various levels of randomness can be achieved. Randomness can be achieved depending on microscopic features of the waveguide that are not predeterministically formed during fabrication (e.g., cannot be predeterministically formed during fabrication), i.e., beyond the control of the manufacturer. The waveguide can be fabricated according to one or more of the following methods: optical lithography, projection lithography, and electron beam lithography, and etching. For example, a waveguide line edge roughness of about 6 nm (e.g., about 3 nm to about 10 nm) can be obtained.

[0051] Line edge roughness (LER) may be defined according to the usual definition in the industry, where LER=3σ, where σ is the standard deviation defined as:

[0052]

number

[0053] where x i is the edge position measured at a given point i along the edge among N distinct points along the edge, i=1 to N,

[0054]

number

[0055] is the average of all N measured edge positions. All edge positions are measured relative to a common reference line (e.g., an imaginary "perfect" edge position). i LER is typically measured using images (or other data) generated by a Critical Dimension Scanning Electron Microscope (CD-SEM). Although images (or other data) generated by an Atomic Force Microscope (AFM) can provide more accurate values ​​at larger correlation lengths, CD-SEM is faster and has become the industry standard. CD-SEM images are processed using software to obtain the edge positions (x i ) can be extracted. One example is PROSEM (see https: / / prosem.genisys-gmbh.com / ). PROSEM is a software package designed for this purpose and is available from GenISys GmbH, Eschenstr. 66, D-82024 Taufkirchen (Munich), Germany.

[0056] The nature of the sidewall roughness (e.g., microscopic features) can provide the desired level of randomness. The design of the optical mode mixing layer, including the waveguide dimensions, spacing and length, can be optimized during manufacturing to provide sufficient variation between different layers within the PUF device and between successive PUF devices / copies.

[0057] In embodiments of the present technology according to any aspect of the present invention, the spacing of the evanescent coupling waveguides and / or the length over which the evanescent coupling waveguides are in close proximity to one another may be determined by the respective optical mode mixing layers (K j) can be pre-determined such that the strength of the evanescent coupling at is determined by the combination of this spacing and length.

[0058] A lateral distance (i.e., "s", the spacing lateral to the waveguide axis) may be defined between adjacent or neighboring waveguides. The lateral distance may vary between adjacent or neighboring waveguides such that the separation between adjacent waveguides is greater for some adjacent or neighboring waveguides or less for some other adjacent or neighboring waveguides.

[0059] In an embodiment, two or more of the separation distances "s" may be the same. Distance "l" indicates the longitudinal length over which the waveguides are coupled. The degree of coupling can be adjusted by changing the values ​​of one or more of the parameters "s" and "l".

[0060] BRIEF DESCRIPTION OF THE DRAWINGS In order that the present disclosure may be more readily understood, a preferred embodiment thereof will now be described, by way of example only, with reference to the accompanying drawings in which: FIG. 1 is a schematic diagram of an apparatus embodying the present disclosure; FIG. 2 is a schematic diagram of components of an apparatus embodying the present disclosure; FIG. 3 is a schematic diagram of components of an apparatus embodying the present disclosure; 4A and 4B show certain components of an apparatus embodying the present disclosure; 5A and 5B are schematic diagrams showing certain portions of an apparatus embodying the present disclosure; FIG. 6 is a schematic diagram illustrating certain components of a device embodying certain aspects of the present disclosure; FIG. 7 is a flow diagram illustrating a method for operating a device embodying an aspect of the disclosure. FIG. 8 is a flow diagram illustrating a method for manufacturing a device embodying an aspect of the present disclosure.

[0061] Detailed Description of the Disclosure Referring to FIG. 1, an apparatus 10 is shown that includes a photonic physically unclonable function (PUF) device 20, a security controller 30 for controlling the PUF device 20, and a computer-readable storage medium 40 that includes instructions for a processor to operate the security controller 30. In embodiments of the present technology, the apparatus 10 may be incorporated into or form part of the apparatus and used as part of an authentication operation of the apparatus, for example as part of a mobile phone, computer, or other electronic or non-electronic device. In embodiments of the present technology, the apparatus 10 may be connected to other apparatus (e.g., electronic devices) and used therewith to perform authentication operations. The processor may be formed as part of the apparatus 10 or may form part of the apparatus in which it is incorporated or to which it is connected.

[0062] Referring to FIG. 2, a PUF device 20 according to an embodiment of the present technology is shown in schematic form. The PUF device 20 may be realized as a classical device, i.e., a device that handles classical light (e.g., laser light), or as a quantum device, i.e., a quantum device that handles light as a quantum state. The PUF device 20 may include a photonic processing network 50, a reconfigurable photonic network 60, and an optical measurement device 70. The term photonic processing network refers to an optical interferometer circuit that is part of a broader optical interferometer that forms the PUF device 20. In an embodiment of the present technology, the PUF device 20 is an integrated photonic chip. The photonic chip may be formed of materials including, but not limited to, silicon (Si), silicon nitride (SiN), silica (SiO2), gallium arsenide (GaAs), indium phosphide (InP), polymer, lithium niobate (LiNbO), or aluminum nitride (AlN).

[0063] Referring to Figure 3, the PUF device 20 is for processing the initial optical mode distribution as part of the challenge C to output a final optical mode distribution, which corresponds to or from which a response R can be derived. Referring to Figure 3, the photonic processing network 50 processes M optical modes (M i ) may be included in the M optical modes (M i ), an initial optical mode distribution is given, and the M optical modes (M i ), the final optical mode distribution is generated. The photonic processing network 50 generates the optical modes (M i ) and are spaced apart along the optical mode (M i ) coupled to K optical mode mixing layers (K j Each optical mode mixing layer (K j The optical mode distribution exiting each optical mode mixing layer (K j ) so that the optical mode distribution received by each optical mode mixing layer (K j ) is the optical mode (M i ) is mixed. In an embodiment, the final optical mode distribution is determined by the final optical mode mixing layer (K K ;j=K), that is, the final optical mode mixing layer is the optical mode (M i ) is the optical mode distribution after acting on

[0064] In the embodiment of the present technology, the optical mode (M i ) are formed or supported on the respective waveguides (i.e., M i may be considered to refer to the waveguide 52, where i=1 to M (e.g., M≧3, or M≧5, or M≧10). j ) supports multiple optical modes (M i) to provide mixing of the M optical modes. An example of a continuous evanescently coupled waveguide suitable for use with this embodiment of the disclosure is the random walk described in Paesani et al. Nature Physics 15, 925 (2019). i are the respective waveguides M i (i.e., M i may be taken to refer to waveguide 52, where i=1 to M). In an embodiment, the continuous evanescent coupling waveguide is a waveguide (M i ) area.

[0065] In embodiments of the present technology, the spacing between the evanescent coupling waveguides and / or the length over which the evanescent coupling waveguides are in close proximity to one another is determined by the respective optical mode mixing layers (K j ) is predetermined such that the strength of the evanescent coupling at the first waveguide 122 is determined by a combination of this spacing and length and the microscopic characteristics of the waveguide that cannot be predetermined during fabrication, i.e., the microscopic characteristics are beyond the control of the manufacturer.

[0066] Referring to FIG. 5A and FIG. 5B, FIG. 5A shows an optical mode (M i5B ) is formed. Distance "s" indicates the respective lateral (short) distance between adjacent or neighboring waveguides (see FIG. 5B ). In an embodiment, the lateral distance "s" may be different between adjacent or neighboring waveguides such that the separation "s" is larger for some adjacent or neighboring waveguides or smaller for some other adjacent or neighboring waveguides. In an embodiment, two or more separations "s" may be the same. Distance "l" indicates the longitudinal length over which the waveguides are coupled. The degree of coupling can be adjusted by varying one or more of the parameters "s" and "l".

[0067] The photonic processing network 50 includes an optical phase shifter φ ji Column (S k The optical phase shifter φ ji Column (S k ) is the optical mode (M i ) and are spaced apart along the optical mode (M i ) and applies an optical phase shift (one or more) determined by or derived from challenge C to generate an optical mode (M i ) are then mixed in the respective optical mode mixing layers (K j ), where j is the optical phase shifter φ ji and the adjacent optical mode mixing layer, i is the optical phase shifter φ ji The optical mode / waveguide to which i In the embodiment, the optical phase shifter φji is k ) may be coupled to each of the multiple optical modes or to a subset thereof. Furthermore, in embodiments, there may be fewer rows of optical phase shifters such that there are no rows of optical phase shifters between adjacent optical mode mixing layers. jiare devices that can be independently controllable to induce an optical phase shift. For example, the optical phase shift may be implemented as a localized refractive index change induced by effects including, but not limited to, thermo-optic, electro-optic, carrier injection, piezoelectric, birefringent, microelectromechanical, strain-induced, or acousto-optic effects.

[0068] According to an embodiment of the present technique, a series of optical phase shifters (S k ) is the optical mode / waveguide (M i ) along the length (direction) of the optical mode mixing layer (K j ) may be arranged alternately with the optical mode mixing layers j=1 to K, i.e., a total of K, and the optical phase shifter rows k=1 to K+1, i.e., a total of K+1. As a result, in the embodiment, the optical phase shifter rows S K+1 , for use in downstream interferometric measurements. i In an embodiment, the array of optical phase shifters S K+1 may not exist, and only a row of optical phase shifters, k=1 to K, may be present.

[0069] In an embodiment according to the present technology, multiple rows of optical phase shifters (S k ) or multiple rows of optical phase shifters (S k ) for each of the optical phase shifters φ ji , the optical mode / waveguide (M i ) are coupled to each of the optical mode mixing layers (K j ) or an optical mode mixing layer (K j ) by each of the optical modes (M i ) or optical mode (M i ) are mixed, e.g., optical modes (M i ) or optical mode (M i) are mixed in their amplitudes. Here, mixing means mixing the optical modes (M i ) light in at least three optical modes, for example, at least three adjacent or neighboring optical modes (M i In an embodiment according to the present technology, a row of optical phase shifters (S k ) for each of the optical phase shifters φ ji are the optical mode / waveguide (M i ) and is coupled to one of the optical mode mixing layers (K j ) by each of the optical modes M i or optical mode M i In the embodiment in which the optical mode mixing layer is a continuous evanescently coupled waveguide, all of the optical modes (M i ) is formed in three or more of the waveguides, or optical modes (M i ) are coupled together.

[0070] In the embodiment, an optical mode mixing layer (K j ) or an optical mode mixing layer (K j ) are all optical modes (M i ) or optical mode (M i ) and the optical mode (M i ) or the optical mode (M i ) includes a continuous evanescent coupling waveguide that provides mixing of the respective amplitudes.

[0071] In this specification, at least three optical modes (M i References to "at least three" in the context of at least three evanescently coupled waveguides may include, for example: four or more optical modes (M i ), and / or 4 or more evanescently coupled waveguides; 5 or more optical modes (Mi ), and / or 5 or more evanescently coupled waveguides; 10 or more optical modes (M i ), and / or 10 or more evanescently coupled waveguides; 10 or more optical modes (M i ), and / or 10 or more evanescently coupled waveguides. As mentioned above, the evanescently coupled waveguides may perform mixing of multiple optical modes such that a random walk of photons occurs between the multiple optical modes and / or between the multiple evanescently coupled waveguides. This effect has been found to be significantly enhanced when the number of modes and / or waveguides involved in the mixing process is increased beyond two.

[0072] As will be explained later, the processor is configured to execute instructions on the computer-readable storage medium 40 to issue a challenge C to the security controller 30 and receive a response R from the security controller 30 .

[0073] The security controller 30 transforms the challenge C and provides the transformed challenge C to the PUF device 20. The security controller then receives the final optical mode distribution output by the PUF device 20 and transforms it into a response R.

[0074] The security controller 30 for operating the PUF can be realized via a standard digital electronics microcontroller or via a field programmable gate array (FPGA) that can be packaged together with or directly co-integrated with the integrated photonics chip on which the PUF device 20 is formed. The challenge C is received by the security controller 30 through wireless transmission (e.g., RF waves, light waves) or through a wired connection (e.g., digital lines formed by DC electronics). Each optical phase shifter φ ji is 2 n, n=n ... The digital-to-analog converter may be electrically connected to a phase shifter to implement a desired operation.

[0075] Specifically, with reference to FIGS. 4A and 4B, a reconfigurable photonic network 60 includes an input section connectable to a single input optical mode I and an optical mode / waveguide (M i ) output section O i and , which result in an input and output distribution of the initial optical mode, respectively. The reconfigurable photonic network 60 may include an optical phase shifter (R s) in the case of a linear array of Mach-Zehnder interferometers (as shown in FIG. 4A), a triangular or rectangular array of universal input interferometers (not shown), or a binary tree array of Mach-Zehnder interferometers (as shown in FIG. 4B). Reconfigurable photonic network 60 prepares (creates) an initial distribution of states, i.e., amplitudes across multiple optical modes, for processing by photonic processing network 50. Reconfigurable photonic network 60 may, for example, generate an optical mode (M i ) such that any desired initial optical mode distribution can be obtained by converting light from a single input optical mode I into a linear optical state, which in turn is converted into multiple optical modes (M i ), in an embodiment, the security controller 30 may use the optical mode distribution information, e.g., the measured optical mode distribution output from the photonic processing network 50, to cause the reconfigurable photonic circuit to adopt a corresponding configuration to generate a new initial optical mode distribution.

[0076] The PUF device 20 may include a light source S (see FIG. 2 ). An initial optical mode distribution is generated from the light source S. If provided, the light source may be connected to a single input optical mode I of the reconfigurable photonic network 60 or to an optical mode waveguide 52 (M i ) may be directly connected to the optical source 52 (M ). The optical source may include a laser (e.g., an electrically pumped integrated laser), an LED light source with a narrow optical spectrum, or quantum state light (e.g., squeezed light or single photons). In an embodiment of the present technique, instead of having a single input optical mode and generating a distribution from the single input optical mode through the use of a reconfigurable photonic network 60, multiple optical modes and / or multiple optical mode waveguides 52 (M i) (e.g., distribution over spectral modes in a fiber / broadband network).

[0077] The optical mode (M i An optical measurement device 70 may be coupled to the optical mode (i.e., the waveguide 52 that forms or supports that mode) to measure the final optical mode distribution of the mode. The optical measurement device 70 may include a photodiode or single-photon detector, or, in embodiments where the PUF is implemented as a quantum device, a superconducting nanowire, a superconducting transition edge sensor, an avalanche photodiode, or a homodyne detection scheme.

[0078] In an exemplary embodiment of a PUF that includes on-chip electronic logic and an integrated photodetector as the optical measurement device 70, the photocurrent from the photodetector may be amplified and converted to a digital signal through an analog-to-digital converter.

[0079] Device 10 may be fabricated using (but need not be) known techniques for integrated photonic devices to produce device 10 having the structure described with respect to embodiments of the present technique.

[0080] The operation of device 10 according to an embodiment of the present technology to obtain a challenge-response pair will now be described.

[0081] First, a set of challenges C' is generated, where each unique challenge is denoted as C. The processor may randomly generate multiple challenges C' in the form of a bit string. Each challenge C may be generated by, for example, s and / or a sequence of optical phase shifters (S k) may include initial optical mode distribution information in the form of settings for setting the challenge C. The optical phase shifter setting information may be obtained directly from the bit string forming the challenge C, or the optical phase shifter setting information may be obtained / derived (e.g., transformed) indirectly from the bit string by employing a hash function or other algorithm. The security controller 30 may be configured to determine the optical phase shifter settings from the bit string forming the challenge C when challenge C is issued by the processor.

[0082] In an embodiment, the challenge C may be a concatenated bit string of length n(KM+I), where I is the optical mode (M i ) to generate the initial optical mode distribution, and n is the number of optical phase shifters Rs and phase shifters φ ji where K is the phase shifter bit resolution of n bits and K is the number of optical phase shifter strings. The bit string thus represents the total number of programmable phase shifters multiplied by the phase shifter resolution n bits. Alternatively, in an embodiment, a bit string of a different length may be issued as the challenge C, and the security controller 30 includes a method for mapping the received challenge C to the phase shifter settings of the PUF device 20. The challenge may be processed by a digital-to-analog converter to determine the on-chip voltage (i.e., phase) to be set on the optical chip modulator of the phase shifter.

[0083] For each challenge C, the security controller 30 selects a sequence of optical phase shifters (S k ) and optical phase shifter R s The reconfigurable photonic network 60, configured according to these settings, then generates an initial optical mode distribution that is provided to the optical modes of the photonic processing network 50 (i.e., to the waveguides 52 that create or support the modes). The initial optical mode distribution is modified by optical phase shifting under the operation of the first series of optical phase shifters (S1), after which the first optical mode mixing layer (K1) mixes multiple optical modes (M i) to couple together at least a subset of the optical modes (M i ) is transformed under the mixing that occurs between the first optical mode mixing layer (K1). As a result, the optical mode distribution leaving the first optical mode mixing layer (K1) is a different distribution. This sequence continues until the light propagates to the end of the photonic processing network 50. The final optical mode distribution is output by the photonic processing network 50 and measured by the optical measurement device 70. The final optical mode distribution measured by the device 70 may then be converted (e.g., digitized) by the security controller 30 into a response R in a form including, but not limited to, a bit string and provided to the processor. In an embodiment, the response R may be further processed by an electronic (analog or digital) function (e.g., a hash function) to improve the randomness and / or security of the PUF.

[0084] In an embodiment, the response R may correspond to a result derived from a light intensity / amplitude (or correlated photon measurement) read out by a photodiode used as the optical measurement device 70 (or, in case the PUF is implemented as a quantum system, a device sensitive to quantum states, e.g., a single photon detector). In the case of light intensity / amplitude, the security controller 30 may obtain a photocurrent through the use of an analog-to-digital converter that digitizes the output, or may obtain a calibrated power measurement that is passed to the security controller 30 in digital form. The security controller 30 may operate in an optical mode (M i ) and discretizes these into 2m levels (i.e., m bits). Subsequent digital post-processing of the concatenated bit string from each photodiode readout (information) may be performed via methods including, but not limited to, hashing or exclusive-OR (XOR) operations on equal-length subdivisions of the full-response bit string. Finally, the digital response bit string may be returned from the security controller 30 via a wireless or wired connection.

[0085] This process is repeated for each challenge C for the set of challenges C', generating a set of challenge-response pairs CRP'.

[0086] The device 10 may be embedded in or connected to another device for use by a trusted client A. The device 10 is then securely provided to the client A in a trusted manner along with a set of challenge-response pairs CRP'.

[0087] Client A may then provide device 10 to client B. If client A wishes to authenticate the identity of client B, client A may issue client B a challenge C from the original set of challenges C'. Client B then obtains a response R and communicates this to client A. If response R matches one held for the corresponding challenge in the original set CRP' of challenge-response pairs, trust is established.

[0088] Alternatively, a creator or manufacturer may create device 10 and provide it to client A. Client A then obtains a set of challenge-response pairs CRP' in the same manner as described above, prior to providing device 10 to client B. Authentication of client B for establishing a secure connection can then proceed in the same manner for each communication between client A and client B.

[0089] An array of PUF devices utilizing alternating rows of optical phase shifters and optical mode mixing layers can obtain an exponentially large number of possible challenge-response pairs, which changes nonlinearly as the number of optical mode mixing layers increases. Furthermore, even if two PUF devices according to embodiments of the present technology are manufactured by the same manufacturing method, the physical realizations of those PUF devices will still be unique and distinct from one another. This is due to microscopic features of the waveguides that form the optical mode mixing layers (e.g., roughness of the walls of the waveguides) that cannot be pre-determined during manufacturing (i.e., beyond the control of the manufacturer). These features affect the phase and coupling strength between the waveguides, and thus the mixing characteristics for each optical mode mixing layer. The degree of randomness thus introduced can be advantageously enhanced by increasing the length that the waveguides are close to one another over a length and / or the separation between the waveguides. The optical mode mixing layers are substantially random unitary transformations that act on the optical mode distributions that each optical mode mixing layer receives.

[0090] Depending on the fabrication technique used (including optical lithography, projection lithography, and electron beam lithography) and the etch used to define the waveguide layer, various levels of randomness can be achieved. For example, with dry projection lithography, a target waveguide dimension distribution of sigma ~1 nm and line edge roughness ~6 nm can be achieved. Figure 5B shows a waveguide so fabricated. The nature of the sidewall roughness can be seen in the figure. The design of the optical mode mixing layer, including the waveguide dimensions, spacing, and length, is optimized to provide sufficient variation between the various layers and PUF copies.

[0091] Next, an embodiment of a further aspect of the present technology will be described with reference to FIG.

[0092] 6 illustrates generally a photonic physical unclonable function (PUF) device 200. The PUF device 200 may be compatible with the photonic processing network 50 of the PUF device 20 described above.

[0093] The PUF device 200 is for processing an initial optical mode distribution, which may be based in part on a challenge C, and outputting a modified optical mode distribution. The PUF device 200 is for processing an initial optical mode distribution, which may be based in part on a challenge C, and outputting a modified optical mode distribution. i , M in total) for which an initial optical mode distribution is provided, from which a modified optical mode distribution is generated. The PUF device 200 includes optical mode mixing layers (K , M in total) spaced along the optical mode and coupled to the optical mode (i.e., coupled to an optical mode waveguide 72 for forming or supporting the optical mode). j ) The optical mode mixing layer (K j ) for each optical mode mixing layer (K j The optical mode distribution exiting each optical mode mixing layer (K j ) so that the optical mode distribution received by each optical mode mixing layer (K j ) is the optical mode (M i The PUF device 200 mixes the optical modes (M i ) to the optical mode waveguide 72. k ) The optical phase shifter array (S k ) is the optical mode mixing layer (K i ) before being received by the optical mode (M i) to change the phase of each of the photonic PUF devices 200. The PUF device 200 may include a security controller for controlling the photonic PUF device 200. The security controller may transform the challenge C and provide the transformed challenge C to the photonic PUF device 200. The security controller may then transform the final modified optical mode distribution output by the photonic PUF device 200 into a response R.

[0094] Optical mode mixing layer (K j ), Optical Mode (M i ) and an optical mode waveguide 72 for forming or supporting an optical mode, as well as an array of optical phase shifters (S k ) may be the same or similar to those described with respect to previous embodiments of the present technology. In embodiments of the present technology, the optical mode mixing layers may be configured in various ways. For example, each optical mode mixing layer may mix the optical mode M i The optical fiber may include a number of Mach-Zehnder interferometers configured to mix light traveling between the sets of optical fibers.

[0095] The PUF device 200 may include one or more elements, such as an optical measurement device, a light source, in the same or similar manner as the PUF device 20 described with respect to the previous embodiment of the present technology.

[0096] The main difference between the PUF device 200 and those described with respect to the previous embodiments is that the security controller is configured to operate the photonic PUF device 200 to generate the final modified optical mode distribution by an iterative process as shown in FIG.

[0097] The iterative process includes an initial step a) in which challenge C is used to set an initial optical mode distribution for processing by the PUF device 200. Challenge C is also used to set an optical phase shifter in the PUF device 200. In step b), the security controller obtains the modified optical mode distribution output by the PUF device 200. In step c), the security controller provides the amplitude of the modified optical mode distribution to the PUF device 200, for example through a feedback circuit or through the use of the security controller, to be processed as a further initial optical mode distribution. For example, the security controller may use the amplitude received from step c) to derive an optical phase shifter setting for configuring the reconfigurable switch network to generate the desired further initial optical mode distribution, or may derive a new phase shifter setting in the PUF device 200, or both. Steps b) through c) are then repeated T times to generate a final optical mode distribution.

[0098] The operation of the PUF device 200 may be further complicated in that the security controller iteratively operates the PUF device 200 to obtain a final optical mode distribution, and as part of step c), the security controller iteratively operates the sequence (S k ) optical phase shifters, and the PUF device may be configured to process a further initial optical mode distribution based on the changed settings. k A set of (R,R) may, in an embodiment, be obtained from a challenge C. A response R to a particular challenge C may correspond to a transformed version of the final optical mode distribution. In an embodiment, the response R may be transformed from one or more or all of the modified optical mode distributions obtained in step b). In an embodiment, a function may be applied to each modified optical mode distribution to generate further initial optical mode distributions for use in the next iteration.

[0099] In an embodiment, the security controller may in step c) transform the modified optical mode distribution and provide the modified optical mode distribution to the PUF device for processing as a further initial optical mode distribution. In an embodiment, if the PUF device includes on-chip electronic logic, transforming the modified optical mode distribution may include applying a cryptographic logic operation by converting the modified optical mode distribution to a digital measurement result through an analog-to-digital converter coupled to a detector of the optical measurement device 70. This further amplifies the randomness before the transformed modified optical mode distribution is processed as a further initial optical mode distribution. The settings of the phase shifters are updated accordingly for subsequent operations of the PUF device a desired number of times, T, until a final optical mode distribution is obtained.

[0100] PUF device 200 is advantageous in that the number of available challenges and associated responses can be increased without creating a larger PUF device, simply by increasing the number of iterations.

[0101] In an embodiment according to the present technology, the PUF device 200 includes an input section connectable to a single input optical mode and an optical mode M. iand (one or more) outputs connectable to the PUF device 70. Here, in step a), the security controller may be configured to use the challenge C to cause the reconfigurable photonic network to adopt a corresponding configuration for generating the initial optical mode distribution. Also, in an embodiment, in step c), the security controller may be configured to use the modified optical mode distribution to cause the reconfigurable photonic network to adopt a corresponding configuration for generating and providing the modified optical mode distribution to the PUF device. For example, the security controller may obtain a measurement of the modified optical mode distribution, e.g. if the PUF device 200, or an apparatus of which the PUF device 200 is part, includes an optical measurement device similar to the optical measurement device 70, and may be configured to calculate the optical phase shifter settings of the reconfigurable photonic network required therefor to generate a further initial optical mode distribution based on the modified optical mode distribution. Furthermore, for embodiments of the present technology in which the security controller transforms the modified optical mode distribution and provides the transformed modified optical mode distribution to the PUF device 200, the security controller may be configured to calculate required optical phase shifter settings for the reconfigurable photonic network to generate a further initial optical mode distribution based on the transformed modified optical mode distribution.

[0102] According to one aspect of the present technology, a method for fabricating a Physical Unclonable Function (PUF) is described with reference to Figure 8. The PUF is formed as a photonic chip.

[0103] The method comprises, in step a), selecting an optical mode (M i ) (i.e., an optical mode waveguide for creating or supporting an optical mode). i ), a predetermined initial optical mode distribution is given for that optical mode (M i) from which the final optical mode distribution can be generated in use. Step b) includes providing an optical mode mixing layer (K ​​) spaced along and coupled to the optical mode (i.e., an optical mode waveguide for forming or supporting the optical mode). j ) is provided. j ) is the optical mode distribution that exits each optical mode mixing layer (K j ) to make the optical mode distribution different from that received by each optical mode mixing layer (K j ) is the optical mode (M i ) are mixed. Step c) is to form an optical mixing layer (K j ) at the front and rear points of the optical mode mixing layer (K j ) is coupled to an optical mode / waveguide (M i Step d) includes forming an optical coupling interface to the optical mixing layer (K j Step e) includes performing tomography through the optical coupling interface to determine an optical mode mixing operation of the optical mixing layer (e.g., to determine an optical mode unitary transformation that maps an input optical mode distribution to an output optical mode distribution from each optical mixing layer). Step e) includes removing the optical coupling interface after step d) is completed to complete the PUF.

[0104] In an embodiment, the method further comprises: j ) by applying a predetermined optical phase shift (one or more) to the optical mode (M i ) arranged at intervals along and coupled to an optical mode (i.e., an optical mode waveguide for forming or supporting the optical mode) to change the phase of each of the optical modes. k ), and in step c) the optical coupling interface is provided with a row (S k ) and / or each (subsequent) series of optical phase shifters (S k+1) is attached to the point before it.

[0105] This method allows one to virtually determine the complete unitarity for each optical mixing layer. More specifically, the optical mode (M i ) is a fully unitary operation on the (characterized) optical mixing layer (K j ) and a row of optical phase shifters (S k ) which allows the manufacturer of the PUF to know the function that relates every challenge C to each response R, and thus allows the manufacturer to calculate every possible CRP without probing the PUF. The individual optical mode mixing layers (Kj) are then made optically inaccessible after manufacture to determine their unitarity; that is, the optical coupling interface is erased by physically and permanently modifying the PUF, i.e. the optical coupling interface. As a result, access to this information by (unauthorized) third parties is precluded.

[0106] The optical coupling interface may be a variety of devices or components that may then be removed in step e. For example, the optical coupling interface may include a grating coupler that applies a periodic perturbation of the refractive index to scatter light out of the plane of the PUF, or it may include a beam splitter optical tap with high reflectivity that couples light into and out of the PUF, or it may include an integrated photodiode.

[0107] The tomography in step d) is performed for each optical mode Mi separately and / or for each optical mode mixing layer (K j) are performed separately. Step d) may include varying the light input and / or light phase shifter settings of each optical mode entering the respective optical mode mixing layer during the tomography process and measuring the amplitude of the output light from each optical mode exiting the respective optical mode mixing layer. An example of a tomography technique that may be used in step d) can be found in the literature "Optics Express, Vol. 21, Issue 11, pp. 13450-13458 (2013) authored by Saleh Rahimi-Keshari, Matthew A. Broome, Robert Fickler, Alessandro Fedrizzi, Timothy C. Ralph, and Andrew G. White". Optical mode M i For each of the ensembles of light input states for each optical mixing layer K j The intensity / amplitude of the light output from each optical mixing layer K is recorded. Using reconstruction (e.g., PhaseLift - an example of this technique is described in arXiv:2010.00517 [Physics.Optics] authored by Daniel Suess, Nicola Maraviglia, Richard Kueng, Alexandre Mainos, Chris Sparrow, Toshikazu Hashimoto, Nobuyuki Matsuda, David Gross, and Anthony Laing), j The transformation unitary matrix of each optical mixing layer K j By repeating this process for , the manufacturer can reconstruct all the parameterized unitary transformations and obtain the underlying functions that map all challenges C to responses R.

[0108] After the complete tomography of the PUF device is completed in step d), the optical coupling interface is destroyed through a physical or chemical post-process. For example, a grating coupler, if used as part of the optical coupling interface, could be exposed to ultra-intense pulsed laser radiation to damage the component so that it no longer diffracts light and the input / readout mechanism is terminated. Alternatively, modification of the optical coupling interface can be achieved through focused ion beam bombardment, electron beam lithography, chemical etching of structures through oxide windows, or thermal annealing and out-diffusion of implanted ion dopants optical couplers (see, for example, patent document "Erasable ion implanted optical couplers", WO2011142913A3). Furthermore, if a readout photodiode is used, it could be disabled through electrostatic discharge or bias (forward or reverse) above the electronic damage threshold.

[0109] It will be readily appreciated that the method according to the described embodiment is advantageous in that it allows the manufacturer to have all the CRP information without the need to probe the PUF device after manufacture.

[0110] The method according to the described embodiments can be employed for various PUF device architectures whose tomography is important for the purposes of deriving CRP information and which may have sequential configurations in how they operate and respond to light input. The method can be used with any of the PUF devices described in this application, but also with other PUF devices as well, without departing from the scope of the present invention.

[0111] As used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted as excluding the presence of other features, steps or components.

[0112] The invention also broadly applies to any combination of two or more parts, elements, steps, examples, and / or features, individually or collectively, referred to or illustrated herein. In particular, one or more features of any embodiment described herein may be combined with one or more features from any other embodiment(s) described herein.

[0113] Protection may be sought for any feature disclosed in any one or more of the publications referenced herein in combination with the present disclosure.

[0114] Although certain exemplary embodiments of the present invention have been described, the appended claims are not intended to be limited to only these embodiments, and the claims should be construed literally, flexibly, and / or to encompass equivalents.

[0115] The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in particular forms or in terms of means for performing the disclosed functions, or methods or processes for obtaining the disclosed results, may be utilized separately or in any combination of such features, as appropriate, to realize the invention in various of its forms.

[0116] While the present invention has been described in conjunction with the exemplary embodiments set forth above, many equivalent modifications and variations will be apparent to those skilled in the art given this disclosure. As such, the exemplary embodiments of the present invention set forth above are considered to be illustrative and not limiting. Various changes may be made to the described embodiments without departing from the spirit and scope of the present invention.

[0117] For the avoidance of doubt, any theoretical explanations provided herein are provided for the purpose of enhancing the understanding of the reader, and the inventors do not wish to be bound by any of these theoretical explanations.

[0118] Any section headings used herein are for organizational purposes only and should not be construed as limiting the subject matter described. Throughout this specification, including the claims that follow, unless the context otherwise requires, the words "comprise" and "include," as well as variations such as "comprises," "comprising," and "including," are to be understood as meaning the inclusion of a recited integer or step, or group of integers or steps, but not the inclusion of any other integer or step, or group of integers or steps. It should be noted that as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from "about" one particular value and / or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values ​​are expressed as approximations, by use of the antecedent "about," it is understood that the particular value forms another embodiment. The term "about" in reference to numerical values ​​is optional and means, for example, ±10%.

[0119] [References] Paesani et al.: Nature Physics 15, 925 (2019). Saleh Rahimi-Keshari, Matthew A. Broome, Robert Fickler, Alessandro Fedrizzi, Timothy C. Ralph, and Andrew G. White:Optics Express, Vol.21, Issue 11, pp.13450-13458 (2013). Daniel Suess, Nicola Maraviglia, Richard Kueng, Alexandre Mainos, Chris Sparrow, Toshikazu Hashimoto, Nobuyuki Matsuda, David Gross, and Anthony Laing: arXiv:2010.00517 [Physics.Optics]. WO2011142913A3 [Brief description of the drawings]

[0120] [Figure 1] 1 is a schematic diagram of an apparatus embodying the present disclosure. [Diagram 2] 1 is a schematic diagram of components of an apparatus embodying the present disclosure. [Diagram 3] 1 is a schematic diagram of components of an apparatus embodying the present disclosure. [Figure 4A] 1 illustrates certain components of an apparatus embodying the present disclosure. [Figure 4B] 1 illustrates certain components of an apparatus embodying the present disclosure. [Figure 5A] 1 is a schematic diagram showing a portion of an apparatus embodying the present disclosure. [Figure 5B] 1 is a schematic diagram showing a portion of an apparatus embodying the present disclosure. [Figure 6] 1 is a schematic diagram illustrating certain components of a device embodying certain aspects of the present disclosure. [Figure 7]1 is a flow diagram illustrating a method for operating a device embodying certain aspects of the present disclosure. [Figure 8] FIG. 1 is a flow diagram illustrating a method for manufacturing a device embodying certain aspects of the present disclosure.

Claims

1. An apparatus comprising:

1. A photonic physically unclonable function (PUF) device for processing an initial optical mode distribution based on a challenge C and outputting a final optical mode distribution, comprising: Multiple optical modes (M ｉ ) for forming or supporting a plurality of said optical modes (M ｉ ), the initial optical mode distribution is given, and a number of said optical modes (M ｉ ) from which the final optical mode distribution is generated; and A plurality of the optical mode waveguides M ｉ and a plurality of said optical mode waveguides M ｉ A plurality of optical mode mixing layers (K ｊ ), each optical mode mixing layer (K ｊ ) a plurality of optical modes M ｉ By mixing the optical mode mixing layers (K ｊ ) is the optical mode distribution exiting each optical mode mixing layer (K ｊ ) different from the optical mode distribution received by the optical mode mixing layer (K ｊ )and, A plurality of rows (S) of optical phase shifters spaced along and coupled to the plurality of optical mode waveguides. ｋ ) by applying a predetermined optical phase shift(s) to generate a plurality of said optical modes (M ｉ ) and the subsequent optical modes are mixed in the respective optical mode mixing layers (K ｊ ) a plurality of rows (S) of optical phase shifters received by the ｋ ) and a plurality of said rows (S ｋ ) or a plurality of said rows (S ｋ ) a plurality of rows (S) of optical phase shifters, each of which is coupled to a respective one of a plurality of said optical mode waveguides; ｋ )and, A photonic PUF device comprising: a security controller for controlling the photonic PUF device, receiving the challenge C and providing a response R, the security controller transforming the challenge C and providing the transformed challenge C to the photonic PUF device, the security controller receiving a final optical mode distribution output by the photonic PUF device and transforming the final optical mode distribution into the response R; a computer readable storage medium comprising instructions for a processor to issue a challenge C to the security controller and receive a response R from the security controller; 13. An apparatus comprising:

2. An apparatus comprising:

1. A photonic physically unclonable function (PUF) device for processing an initial optical mode distribution based on a challenge C and outputting a final optical mode distribution, comprising: Multiple optical modes (M ｉ ) for forming or supporting a plurality of said optical modes (M ｉ ), the initial optical mode distribution is given, and a number of said optical modes (M ｉ ) from which the final optical mode distribution is generated; and a plurality of optical mode mixing layers (K) spaced apart along the plurality of optical mode waveguides and coupled to the plurality of optical mode waveguides; ｊ ) each optical mode mixing layer K ｊ The multiple optical modes (M ｉ ) so that the optical mode distribution exiting each mixing layer is ｊ ) a plurality of optical mode mixing layers (K ｊ ), comprising a plurality of said optical mode mixing layers (K ｊ ) or more of said optical mode mixing layers (K ｊ ) each of a plurality of optical modes (M ｉ A plurality of optical mode mixing layers (K ｊ )and, A plurality of rows (S) of optical phase shifters spaced along and coupled to the plurality of optical mode waveguides. ｋ ) by applying a predetermined optical phase shift(s) to generate a plurality of said optical modes (M ｉ ) and the subsequent optical modes are mixed in the respective optical mode mixing layers (K ｊ ) a plurality of rows (S) of optical phase shifters received by the ｋ )and, A photonic PUF device comprising: a security controller for controlling the photonic PUF device, receiving the challenge C and providing a response R, the security controller transforming the challenge C and providing the transformed challenge C to the photonic PUF device, the security controller receiving a final optical mode distribution output by the photonic PUF device and transforming the final optical mode distribution into the response R; a computer readable storage medium comprising instructions for a processor to issue a challenge C to the security controller and receive a response R from the security controller; 13. An apparatus comprising:

3. A plurality of said rows (S ｋ ) or a plurality of said rows (S ｋ For each of the optical mode mixing layers (K), a plurality of said optical phase shifters are coupled to each of a plurality of said optical mode waveguides and / or a plurality of said optical mode mixing layers (K ｊ ) or more of the optical mode mixing layers (K ｊ ) each of a plurality of said optical modes (M ｉ 3. The apparatus of claim 2, wherein all of the components are mixed.

4. a reconfigurable photonic network having an input connectable to support or form a single input optical mode, and one or more outputs connectable to a plurality of said optical mode waveguides; the challenge C includes initial optical mode distribution information; The apparatus of claim 1 , 2 or 3 , wherein the security controller uses the initial optical mode distribution information to cause the reconfigurable photonic circuit to adopt a corresponding configuration for generating the initial optical mode distribution.

5. The reconfigurable photonic network includes a plurality of optical phase shifters (R ｓ 5. The apparatus of claim 4, further comprising:

6. The reconfigurable photonic network reconfigures light from the single input optical mode into multiple of the optical modes (M ｉ 6. The apparatus of claim 4, comprising an array of a plurality of Mach-Zehnder interferometers for transforming the initial optical mode distribution over a range of 10 GHz to a corresponding optical state.

7. a) the challenge C includes information for determining an optical phase shifter configuration, and the security controller uses this information to determine the optical phase shifter configuration to determine the number of said strings (S ｋ ) and / or when claim 4 is directly or indirectly relied upon, a plurality of said optical phase shifters (R ｓ ) to set the b) a plurality of said rows (S ｋ ) and a plurality of said optical mode mixing layers (K ｊ ) are interleaved along the length of the plurality of optical mode waveguides; and c) j=0 to K, k=0 to K+1, and (S Ｋ＋１ ) said row stores a plurality of said optical modes (M ｉ ) for applying said final optical mode distribution adjustment of The apparatus according to any one of claims 1 to 6, comprising one or more of:

8. 1. A photonic physically unclonable function (PUF) device for processing an initial optical mode distribution based on a challenge C and outputting a final optical mode distribution, comprising: Multiple optical modes (M ｉ ) for forming or supporting a plurality of said optical modes (M ｉ ), the initial optical mode distribution is given, and a number of said optical modes (M ｉ ) from which the final optical mode distribution is generated; and a plurality of optical mode mixing layers (K) spaced apart along the plurality of optical mode waveguides and coupled to the plurality of optical mode waveguides; ｊ ), each optical mode mixing layer (K ｊ ) received by the multiple optical modes (M ｉ ) to form each optical mode mixing layer (K ｊ ) is the optical mode distribution exiting each optical mode mixing layer (K ｊ ) to provide a different optical mode distribution from that received by the optical mode mixing layer (K ｊ ), comprising a plurality of said optical mode mixing layers (K ｊ ) each of a plurality of said optical modes (M ｉ ) to receive at least a subset of the plurality of optical modes (M ｉ ) for the subset of the optical mode mixing layers (K ｊ )and, A plurality of rows (S) of optical phase shifters spaced along and coupled to the plurality of optical mode waveguides. ｋ ) by applying a predetermined optical phase shift(s) to generate a plurality of said optical modes (M ｉ ) and the subsequent optical modes are mixed in the respective optical mode mixing layers (K ｊ ) a plurality of rows (S) of optical phase shifters received by the ｋ )and, a security controller for controlling the photonic PUF device, receiving the challenge C and providing a response R, the security controller transforming the challenge C and providing the transformed challenge C to the photonic PUF device, the security controller receiving a final optical mode distribution output by the photonic PUF device and transforming the final optical mode distribution into the response R; a computer readable storage medium comprising instructions for a processor to issue a challenge C to the security controller and receive a response R from the security controller; A photonic physical unclonable function (PUF) device comprising:

9. A plurality of the optical modes (M ｉ ) are formed in each optical mode waveguide, 9. The photonic physical unclonable function (PUF) of claim 8, wherein a plurality of the contiguous evanescently coupled waveguides correspond to a plurality of regions of a plurality of the optical mode waveguides.

10. A plurality of the optical mode mixing layers (K ｊ ) each of a plurality of said optical modes (M ｉ ) to receive at least a subset of the plurality of optical modes (M ｉ ), and optionally or preferably includes a plurality of successive evanescent coupling waveguides that provide mixing of the respective amplitudes of the plurality of optical modes (M ｉ 8. The apparatus of claim 1 , wherein a plurality of successive evanescent coupling waveguides are formed in each optical mode waveguide, the plurality of successive evanescent coupling waveguides corresponding to a plurality of regions of the plurality of optical mode waveguides.

11. The spacing between the evanescent coupling waveguides and / or the length over which the evanescent coupling waveguides are in close proximity to each other may be determined by the respective optical mode mixing layers (K ｊ 11. The apparatus or photonic physical unclonable function (PUF) of claim 8, 9 or 10, wherein the strength of evanescent coupling of the first waveguide to the second waveguide is predetermined such that the strength of evanescent coupling of the first waveguide to the second waveguide is determined by a combination of the spacing and the length and microscopic features of the plurality of waveguides that are not predetermined during fabrication.

12. A plurality of the optical mode mixing layers (K ｊ ) at least one of the optical modes (M ｉ At least three of the optical modes (M ｉ ) to receive all of the plurality of optical modes M ｉ The at least three or more of the optical modes M ｉ 12. An apparatus or photonic physical unclonable function (PUF) according to any one of claims 8 to 11, comprising a continuous evanescent coupling waveguide which provides mixing of the respective amplitudes for all of said amplitudes.

13. the initial optical mode distribution includes a light source generated from the light source; The apparatus or photonic physical unclonable function (PUF) of any one of claims 1 to 12, wherein the light source comprises one or more of a laser, an electrically pumped integrated laser, an LED light source (e.g. having a narrow light spectrum), a quantum state of light (e.g. squeezed light or single photons).

14. a) an optical measurement device connected to a plurality of said optical mode waveguides for measuring said final optical mode distribution, optionally or preferably comprising a photodiode or a single photon detector; b) the photonic physical unclonable function (PUF) comprises an integrated photonic chip, optionally the integrated photonic chip being made of silicon (Si), silicon nitride (SiN), silica (SiO ２ ), gallium arsenide (GaAs), indium phosphide (InP), a polymer, lithium niobate (LiNbO), or aluminum nitride (AlN); and c) the plurality of optical phase shifters may be independently controllable and / or may comprise thermo-optical, electro-optical, piezoelectric, birefringent, micro-electromechanical, strain-inducing, or acousto-optical devices; An apparatus or photonic physical unclonable function (PUF) according to any one of claims 1 to 13, comprising one or more of:

15. 1. A photonic physically unclonable function (PUF) device for processing an initial optical mode distribution based on a challenge C and outputting a modified optical mode distribution, the device comprising: Multiple optical modes (M ｉ ) for forming or supporting a plurality of said optical modes (M ｉ ), the initial optical mode distribution is given, and a number of said optical modes (M ｉ a plurality of optical mode waveguides from which the modified optical mode distribution is generated; a plurality of optical mode mixing layers (K) spaced apart along the plurality of optical mode waveguides and coupled to the plurality of optical mode waveguides; ｊ ), each optical mode mixing layer (K ｊ ) received by the multiple optical modes (M ｉ ) to form each optical mode mixing layer (K ｊ ) is the optical mode distribution exiting each optical mode mixing layer (K ｊ ) a plurality of optical mode mixing layers (K ｊ )and, A plurality of rows (S) of optical phase shifters spaced along and coupled to the plurality of optical mode waveguides. ｋ ) by applying a predetermined optical phase shift(s) to generate a plurality of said optical modes (M ｉ ) and the subsequent optical modes are mixed in the respective optical mode mixing layers (K ｊ ) a plurality of rows (S) of optical phase shifters received by the ｋ )and, a security controller for controlling the photonic PUF device, receiving the challenge C and providing a response R, the security controller transforming the challenge C and providing the transformed challenge C to the photonic PUF device, the security controller receiving a final optical mode distribution output by the photonic PUF device and transforming the final optical mode distribution into the response R; Including, The security controller includes: a) the security controller using the challenge C to set an initial optical mode distribution for processing by the PUF; b) the security controller acquiring the amplitude of the modified optical mode distribution; c) the security controller providing the amplitude of the modified optical mode distribution to the PUF device for processing as a further initial optical mode distribution; d) the security controller repeating steps b) and c) T times to generate the final optical mode distribution; and operating the photonic PUF device to generate the final modified optical mode distribution by an iterative process including:

16. The security controller, as part of step c), ｋ ) of the plurality of optical phase shifters or the plurality of rows (S ｋ 16. The photonic PUF device of claim 15, wherein the PUF device can be configured to process the further initial optical mode distribution based on the changed settings of all of the optical phase shifters of a plurality of the optical phase shifters.

17. The security controller detects the number of rows (S) of optical phase shifters for each iteration of the process. ｋ 17. The photonic PUF device of claim 16, wherein the setting of C is used to set the challenge C.

18. 18. The photonic PUF device of claim 15, 16 or 17, wherein the response R is transformed only from the final optical mode distribution.

19. 19. The photonic PUF device of claim 15, 16, 17 or 18, wherein the response R is transformed from one or more of the modified optical mode distributions obtained in step b) or from all of the modified optical mode distributions obtained in step b).

20. a reconfigurable photonic network having an input connectable to support or form a single input optical mode, and output(s) connectable to a plurality of said optical mode waveguides; The photonic PUF device according to any one of claims 15 to 19, wherein in step a), the security controller uses the challenge C to cause the reconfigurable photonic network to adopt a corresponding configuration for generating the initial optical mode distribution.

21. 21. The photonic PUF device of claim 20, wherein step c) comprises the security controller using the amplitude of the altered optical mode distribution to cause the reconfigurable photonic network to adopt a corresponding configuration for generating the amplitude of the altered optical mode distribution and providing the amplitude to the PUF device.

22. 22. The photonic PUF device of any one of claims 15 to 21, wherein step c) comprises the security controller transforming the modified optical mode distribution and providing the modified optical mode distribution to the PUF device for processing as a further initial optical mode distribution.

23. The photonic PUF device of claim 22, when citing claim 21, wherein the security controller uses the transformed modified optical mode distribution to cause the reconfigurable photonic network to adopt a corresponding configuration for generating the transformed modified optical mode distribution and providing the transformed modified optical mode distribution to the PUF device.

24. 24. The photonic PUF device of any one of claims 15 to 23, comprising an optical measurement device connected to a plurality of said optical mode waveguides for measuring said modified optical mode distribution and said final optical mode distribution, respectively.

25. 1. A method of forming a system including a photonic physically unclonable function (PUF) device for receiving an initial optical mode distribution associated with a challenge C and outputting a final optical mode distribution associated with a response R, and information relating a plurality of challenges C to a plurality of responses R, respectively, comprising: a) Multiple optical modes (M ｉ Providing a plurality of optical mode waveguides for forming or supporting a plurality of said optical modes (M ｉ ), the predetermined initial optical mode distribution may be given for a number of said optical modes (M ｉ ) from which the final optical mode distribution can be generated in use; b) a plurality of optical mixing layers (K) spaced apart along and coupled to a plurality of said optical mode waveguides; ｊ ), each optical mode mixing layer (K ｊ ) received by the multiple optical modes (M ｉ ) to form each optical mode mixing layer (K ｊ The optical mode distribution exiting each optical mode mixing layer K ｊ a plurality of optical mixing layers (K ｊ ) providing a c) a plurality of said optical mixing layers (K ｊ ) each of the optical mixing layers (K ｊ ) at points before and after the optical mode mixing layer (K ｊ forming a plurality of optical coupling interfaces for a plurality of said optical mode waveguides coupled to said optical mode waveguides; d) a plurality of said optical mixing layers (K) that associate a plurality of challenges C with respective responses R; ｊ performing tomography through a plurality of said optical coupling interfaces to determine the optical mode mixing behavior of said optical coupling interfaces; e) removing the plurality of optical coupling interfaces after step d) is completed; and A method comprising:

26. A plurality of rows (S) of optical phase shifters spaced along and coupled to the plurality of optical mode waveguides. ｋ ) by applying a predetermined optical phase shift(s) to generate a plurality of said optical modes (M ｉ ) and the subsequent optical modes are mixed in the respective optical mode mixing layers (K ｊ ) a plurality of rows (S) of optical phase shifters received by the ｋ providing a In step c), the optical coupling interfaces are connected to a series (S) of optical shifters preceding each other. ｋ ) and / or each (subsequent) plurality of optical shifter rows (S ｋ＋１ 26. The method of claim 25, wherein the first point is connected to a point before the second point.

27. Step d) comprises performing said tomography through each optical mode separately and / or for each optical mode mixing layer separately; and / or Step d) is Varying the optical input of each optical mode entering the respective optical mode mixing layer and / or the setting of the optical phase shifter during the tomography process; measuring the amplitude of output light from each optical mode exiting each of said optical mode mixing layers; 27. The method of claim 25 or 26, comprising:

28. A method of operating an apparatus or photonic PUF device according to any one of claims 1 to 24, optionally or preferably comprising using the apparatus or photonic PUF device as part of an authentication process to authenticate a device, a user or communications.

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