Handover between operators of a computer

Abstract

An arrangement 200 for allowing handover of a computer 104 is provided. The computer 104 comprises first and second physical storage media, each comprising at least three different logical storage partitions, and a secret manager 105, comprising an integrity compartment 402, an identity compartment 403, and a handover compartment 404. The integrity compartment 402 comprises one slot for each logical storage partition, each slot comprising an integrity secret to be used for verifying the integrity of the software in the storage partition. The identity compartment 403 comprises first and second slots, each comprising an identity secret associated with an operator, to be used for verifying the identity of the operator and is initialized with an identity secret for a first operator 101 in the first slot. The first slot is only accessible by the first operator 101, and the second slot is not accessible by the first operator 101.

Description

[0001] HANDOVER BETWEEN OPERATORS OF A COMPUTER

[0002] TECHNICAL FIELD

[0003] The present disclosure relates generally to arrangements and methods for allowing handover of a computer between a current and a designated operator.

[0004] BACKGROUND

[0005] Energy-management solutions for the consumer market result in a convergence between operational technology (OT) functions and information technology (IT) infrastructure. Traditionally, OT has been characterized by isolated and deterministic systems, with a main focus on safety and availability, whereas IT systems have been connected, cost-driven, and designed for functionality.

[0006] Typical IT systems in a household include consumer electronics for audio and video applications. Corresponding OT systems in a household include a computer being part of a permanently installed system used to control charging stations, solar-panel installations and battery-storage units.

[0007] Service providers which previously offered fixed bundles, combining internet access, telephony, and media services in a single offering, have been replaced by end-users who procure their own electronic devices and freely choose among service providers. Installation of such IT equipment typically does not require qualified personnel.

[0008] The envisioned energy-efficient and connected smart home however requires professional installation of some devices. This presents both technical and regulatory challenges. The commercial consequence is that consumer electronics retailers may offer telephony services in connection with equipment purchases, but without the underlying technical integration. The technical and commercial aspects are not aligned.

[0009] The cybersecurity triad CIA refers to confidentiality, integrity and availability. As OT systems are critical, availability is often prioritised over confidentiality. A critical component in OT systems is persistent storage, which must be redundant. Highly critical OT systems are often deployed without any network connection. Management using removable physical storage media may therefore be the only feasible option. Open-source software is common in both industrial computers and consumer electronics, as it enables high functionality at low cost. One type of open-source technology is container-based software, which facilitates service management throughout the entire life cycle.

[0010] In defence applications, civilian computers are often required even for military use. The stringent requirements on military systems are decreasing in some contexts, for example as unmanned aerial vehicles may be treated as expendable equipment. There is a need to rely on the civilian market for volume manufacturing and technological adaptability, while ensuring that such technology remains suitable for military applications.

[0011] Existing systems establish only a single cryptographic relationship between one operator and a computer. The energy system is a critical infrastructure and must be resilient to threats, both in times of peace and in crisis.

[0012] PROBLEMS WITH THE PRIOR ART

[0013] In consumer electronics and systems having dual-use characteristics, there is a need to change operators and associated services while retaining an existing and already installed computer. Software provided by an operator may, due to availability requirements, need to be duplicated onto at least two separate physical storage media. The software component responsible for installation should be adapted for execution from random-access memory (RAM). Existing computers and their storage partitioning are not adapted to these requirements. Current computers lack isolation between the partitions needed to fulfil such operational needs.

[0014] According to the National Institute of Standards and Technology (NIST), certain cryptographic algorithms will no longer be permitted in new products. This primarily affects key-distribution strategies over open networks; avoiding weak algorithms introduces challenges for key distribution itself, or requires replacing all vulnerable cryptographic primitives in constrained environments such as firmware.

[0015] Existing technologies, including Arm Trusted Firmware, GSMA specifications and UEFI, rely on asymmetric key-distribution mechanisms and must therefore be updated with more complex algorithms and significantly longer cryptographic keys.

[0016] Academic research has addressed how multiple operators may share a computer. The article “AutoPKI: public key infrastructure for loT with automated trust transfer” by Joel Hoglund et al. (International Journal of Information Security, volume 23, pages 1859-1875) describes how trust transfer depends on lightweight public-key infrastructure for key distribution in certificate-less cryptography.

[0017] When a computer is initialized, for example in a factory environment, such initialization typically occurs in a secure environment. By limiting the use of the secrets required for installation to only support the relationship between the computer and a current operator, a restriction to using only symmetric algorithms does not present an obstacle in this phase.

[0018] Restoring a computer to factory settings is not clearly defined in existing solutions, when the computer may be associated with several operators over time.

[0019] Existing solutions for computer life-cycle management are network-dependent, and not suited for operation in isolation.

[0020] New regulatory requirements mandate that all software components in a computer must be declared. Such lists are seldom used to ensure the integrity of a computer, even though this would constitute a simpler alternative to current TPM-based remote attestation mechanisms.

[0021] Present technologies for incremental updates have become less relevant, as computer software has already been modularised through container-based technologies.

[0022] Operating a large installed base of computers running numerous software versions is a significant challenge.

[0023] The business case for an operator that only provides connectivity is weak. Meanwhile, service providers can share life cycle management methods.

[0024] There is thus a need for arrangements and methods that address these problems.

[0025] SUMMARY

[0026] The above described problem is addressed by the claimed arrangement, where the computer preferably comprises: first and second physical storage media, each physical storage medium comprising at least three different logical storage partitions on which different types of operating systems may be remotely installed: two installer partitions, each configured to contain an installer version of an operating system, and one payload partition, configured to contain a payload operating system; a read-only memory comprising firmware for the computer boot process, the read-only memory being arranged to load the operating system; and a secret manager, comprising an integrity compartment, an identity compartment, and a handover compartment. The integrity compartment preferably comprises one slot for each logical storage partition in the physical storage media, each slot configured to comprise an integrity secret to be used for verifying the integrity of the software in the storage partition. The identity compartment preferably comprises first and second slots, each comprising an identity secret associated with an operator, to be used for verifying the identity of the operator; and is configured to be initialized with an identity secret for a first operator in the first slot, where the first slot is only accessible by the first operator, and the second slot is not accessible by the first operator. The handover compartment is preferably configured to comprise a handover secret that is entered by the current operator, after having been distributed from the designated operator to the current operator. The handover of the computer from a current to a designated operator is preferably configured to always use the handover secret in the handover compartment of the secret manager, which handover secret is usable only once. Either the current or the designated operator must be the first operator.

[0027] This enables handover between different operators to be made via a trusted first operator, by the current operator first handing over to the trusted first operator, and the trusted first operator then handing over to the new operator.

[0028] In embodiments, the arrangement is configured to use a prioritized list in order to select one of the four installer partitions to be used for loading the operating system, the prioritized list defining an order of prioritization for the four installer partitions.

[0029] In embodiments, the arrangement comprises a watchdog unit, arranged to detect failed attempts to load the operating system from a given logical storage partition, wherein upon a failed attempt, the failing installer partition is excluded from the prioritized list.

[0030] In embodiments, the arrangement comprises a signature manifest in each logical storage partition, which signature manifest is arranged to enable integrity verification in order to cryptographically protect files located in the logical storage partition against tampering.

[0031] In embodiments, the integrity secrets, the identity secrets and the handover secrets in the secret manager are based only on symmetric algorithms and / or one-way hash functions, so that verification may be performed by providing both the received and encrypted hash sum and the calculated hash sum as input, returning a result of the operation as a minimal binary verdict. This makes the arrangement quantum resistant. In embodiments, some secrets in the secret manager are arranged to be replaceable by the current operator when they have been used a predetermined number of times. This increases the security of the arrangement.

[0032] In embodiments, the computer is arranged to be restorable so that the first operator becomes the current operator by activating a reset, causing the installation image of the operating system to erase all data. This enables a safe factory reset of the computer.

[0033] The above described problem is also addressed by the claimed method, where the computer preferably comprises: first and second physical storage media, each physical storage medium comprising at least three different logical storage partitions on which different types of operating systems may be remotely installed: two installer partitions, each configured to contain an installer version of an operating system, and one payload partition, configured to contain a payload operating system; a read-only memory comprising firmware for the computer boot process, the read-only memory being arranged to load the operating system; and a secret manager, comprising an integrity compartment, an identity compartment, and a handover compartment. The method preferably comprises configuring the integrity compartment to comprise one slot for each logical storage partition in the physical storage media, each slot comprising an integrity secret to be used for verifying the integrity of the software in the storage partition; configuring the identity compartment to comprise first and second slots, each comprising an identity secret associated with an operator, to be used for verifying the identity of the operator; initializing the identity compartment with an identity secret for a first operator in the first slot, where the first slot is only accessible by the first operator, and the second slot is not accessible by the first operator; distributing a handover secret from the designated operator to the current operator; providing, by the current operator, the handover secret to the computer, for entering into the handover compartment; and effecting handover of the computer from the current to the designated operator using the handover secret, which handover secret is usable only once. Either the current or the designated operator must be the first operator.

[0034] This enables handover between different operators to be made via a trusted first operator, by the current operator first handing over to the trusted first operator, and the trusted first operator then handing over to the new operator.

[0035] In embodiments, the method further comprises using a prioritized list in order to select one of the four installer partitions to be used for loading the operating system, the prioritized list defining an order of prioritization for the four installer partitions. In embodiments, the method further comprises using a watchdog unit to detect failed attempts to load the operating system from a given logical storage partition, and upon a failed attempt, excluding the failing logical storage partition from the prioritized list.

[0036] In embodiments, the method further comprises using a signature manifest in each logical storage partition to enable integrity verification in order to cryptographically protect files located in the logical storage partition against tampering.

[0037] In embodiments, the method further comprises arranging the integrity secrets, the identity secrets and the handover secrets in the secret manager to be based only on symmetric algorithms and / or one-way hash functions, so that verification may be performed by providing both the received and encrypted hash sum and the calculated hash sum as input, returning a result of the operation as a minimal binary verdict. This makes the method quantum resistant.

[0038] In embodiments, the method further comprises arranging some secrets in the secret manager to be replaceable by the current operator when they have been used a predetermined number of times. This increases the security of the method.

[0039] In embodiments, the method further comprises arranging the computer to be restorable so that the first operator becomes the current operator by activating a reset, causing the installation image of the operating system to erase all data. This enables a safe factory reset of the computer.

[0040] In embodiments, the first operator is the manufacturer of the computer. Other operators are typically business operators.

[0041] In embodiments, the first physical storage medium is a fixed storage medium and the second physical storage medium is an exchangeable removable storage medium.

[0042] The computer preferably also comprises a central processing unit and a primary memory.

[0043] The identity secret in the first slot can preferably never be removed, but it can be updated by the first operator.

[0044] Supporting services for the current and designated operator may monitor the handover process and generate an alert if any problem arises.

[0045] The compartments and slots in the secret manager are not physical compartments and slots, but just a way of organizing the access to the secrets in the secret manager. The handover compartment may be realized in the form of a third slot in the identity compartment. The scope of the invention is defined by the claims, which are incorporated into this section by reference. A more complete understanding of embodiments of the invention will be afforded to those skilled in the art, as well as a realisation of additional advantages thereof, by a consideration of the following detailed description of one or more embodiments. Reference will be made to the appended sheets of drawings that will first be described briefly.

[0046] BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figs. 1 a-e is a sequence diagram that describes transactions occurring between five actors, in accordance with one or more embodiments described herein.

[0048] Figs. 2a-c is a sequence diagram that describes how a current Operator2 transfers control of the computer back to Operatori , in accordance with one or more embodiments described herein.

[0049] Fig. 3 illustrates a state diagram comprising three states, in accordance with one or more embodiments described herein.

[0050] Fig. 4a illustrates a secret manager, in accordance with one or more embodiments described herein.

[0051] Fig. 4b illustrates how availability and failsafe handover requirements between operators map to storage partitions, in accordance with one or more embodiments described herein.

[0052] Fig. 5 illustrates the restoring of a computer to factory settings, in accordance with one or more embodiments described herein.

[0053] Fig. 6 illustrates how an operator can change a secret in a computer, in accordance with one or more embodiments described herein.

[0054] Figs. 7a-b is a flowchart describing high-level logic in boot loading, in accordance with one or more embodiments described herein.

[0055] Figs. 8a-d describe scalability aspects of secret distribution, in accordance with one or more embodiments described herein.

[0056] Figs. 9a-c illustrate methods for creating distribution images for the computer, in accordance with one or more embodiments described herein.

[0057] Fig. 10 illustrates a sequence diagram in which a manufacturer provides isolation between two operators, in accordance with one or more embodiments described herein. Figs. 11a-c illustrate a sequence diagram showing the handover procedure between two operators when a computer is not connected to a network, in accordance with one or more embodiments described herein.

[0058] Fig. 12 schematically illustrates a method for allowing handover of a computer between a current and a designated operator, in accordance with one or more embodiments described herein.

[0059] Embodiments of the present disclosure and their advantages are best understood by referring to the detailed description that follows. It should be appreciated that like reference numerals are used to identify like elements illustrated in one or more of the figures.

[0060] DETAILED DESCRIPTION

[0061] Almost all computers today depend on an operator and are required, for both functional and regulatory reasons, to support secure lifecycle management. The operator ensures that the computer can be installed, monitored, updated, and decommissioned in a controlled manner, including the erasing of sensitive data. Without an operator, there would be no trusted entity responsible for maintaining the security and compliance of the payload software that provides value to customers.

[0062] The present disclosure introduces an extended concept involving additional operators, each with clearly defined roles. An initial operator, also referred to as the manufacturer, is responsible for initializing the computer in a trusted environment, with cryptographic secrets and installation software used for the handover of the computer from the current to a designated operator.

[0063] The introduction of additional operators enables improved utilization of the computer without jeopardizing isolation. The initial operator maintains control over the mechanisms for installation, integrity verification, and recovery, while the business operator can focus on payload software.

[0064] A key aspect of the disclosed concept is the isolation between operators. The same computer can support multiple business operators with different payloads over time. Handover between two business operators always includes the initial operator. This enforced involvement of the initial operator ensures isolation.

[0065] When a computer is installed for the first time, only one handover is required, involving the initial operator and the first business operator providing payload software. During handover, a short-lived secret (“handover secret”) and a minimal software (“install software”) are used. During handover, the objective is to transfer control from the current to the designated operator.

[0066] The business operator is responsible for the payload software executed on the computer. If a severe problem in the computer arises, the computer will, after erasing sensitive data, automatically revert control to the initial operator. The initial operator may then act to reinstall the computer without human intervention.

[0067] The payload software can be replaced without replacing the physical computer. In this way, investments in costly installation are preserved. The owner of a computer may request that the current business operator hands over the computer to a new business operator providing equivalent functionality. The disclosed concept thus supports dual use of a computer. One operator may deploy civil payload software. The computer may later, via the initial operator, be handed over to a new business operator deploying payload software with defense capability. For example, drones with an integrated computer may have different payload software, with different regulatory requirements and functionalities, depending on the intended use.

[0068] The disclosed concept enables handover between operators of a computer, regardless of whether the computer is connected to a network or deployed in a solitary environment. The computer may at any time revert to its initial state. The result of a factory reset includes the deletion of all data, software, and secrets associated with the current operator.

[0069] For the computer to achieve high availability, two physical storage devices are desirable. Installation of software is carried out by the install software executed in RAM. The payload software provided by the business operator is expected to be larger, and therefore requires more storage space on the physical storage device than the installer software provided by the initial operator. Each physical storage device is divided into storage partitions. During operation, the computer through its firmware enforces control with these storage partition boundaries. Within each storage partition, file systems are created where software and data are stored. The disclosed concept requires at least six storage partitions. Each storage partition must include a file system readable by the firmware.

[0070] The use of logical storage partitions enables software to be distributed across different physical media. According to the disclosed concept, certain fixed logical storage partitions are bound to the trusted operator / manufacturer. Instead of handover between any business operator, the procedure requires that the trusted operator is special and must always be involved in all handovers. Handover between business operators thus always involves the trusted operator, so that direct handovers between business operators which are not the trusted operator are not permitted.

[0071] To ensure that the computer executes only software issued by a trusted operator, a secret is associated with each storage partition. A secret intended for the computer’s integrity may, after use, be replaced by a new secret, which protects against attacks in which older software is permitted to execute. When the computer has started, the firmware will load software from the default storage partition. By verifying the content of a storage partition using the corresponding integrity secret, it can, before execution, be determined which operator has signed the software. In this way, access to secrets related to identity can be controlled.

[0072] The architecture uses a dual-root of trust model, consisting of two parallel roots of trust. Two types of secrets are used: identity secrets, which signify what type of computer an individual represents, and verifies the relation between the operator and the computer, and integrity secrets, which verify that the software being installed originates from a legitimate operator. All secrets are stored and managed in the secret manager. The initial secrets in the secret manager are deployed by the initial operator in a trusted environment. Distribution of secrets over a public network may employ algorithms resistant to quantum computing attacks.

[0073] The disclosed concept combines existing symmetric algorithms suitable for constrained environments with allowing quantum-resistant algorithms in the installer software for the distribution of secrets.

[0074] Storage partitions are bound to either the current operator or the designated operator. Each storage partition may have a priority, to assure consistency if many storage partitions are available for boot of the computer. The default storage partition defines the first boot option for the computer. A failed boot attempt may be detected by firmware, and the corresponding boot partition may then be set as no longer available. When all storage partitions related to the business operator are unavailable, the system may enter a factory reset state and attempt a new handover to become operational again.

[0075] The computer could at any time enter the initial state. In a networked environment, this could be initiated from the operator towards the computer (for disconnected operation, physical access is required). The result of a factory reset includes the deletion of all images and secrets from any other operator than the trusted operator / manufacturer. When the computer boots and detects a factory reset request, all secrets related to other operators are removed. Upon successful verification of integrity, all data in all other storage partitions are erased. The present disclosure relates generally to handovers between operators of a computer, and more particularly to arrangements and methods for allowing handover of a computer between a current and a designated operator.

[0076] Embodiments of the disclosed solution are presented in more detail in connection with the figures.

[0077] Figs. 1 a-e is a sequence diagram that describes transactions occurring between five actors, according to an example embodiment of the invention. The first actor on the left, 101 , is the Manufacturer / Operatorl . The manufacturer can also be a business operator, or a logistics partner (if one wants to anonymize who receives the product). Operator2, 102, is the business operator which will operate the system, namely the one who offers services. 103 is a time server, to adjust time skew for the computer. 104 is the computer being handed over in this sequence diagram. 105 is the secret manager, a part of the computer where cryptographic secrets are stored and protected, which can communicate securely with the rest of the computer 104.

[0078] The sequence starts in Fig. 1 a with Operator2 ordering a computer, or alternatively wanting to take over a returned computer. In step 106, Operator2 generates and sends a handover secret to Operatori . If Operator2 is an existing computer operator wanting to take over a previously deployed computer, it will also send the serial number to Operatori . If no serial number is provided, this is a new order. The response from Operatori includes the serial number, regardless of whether this is a new or previously deployed computer. Operator2 then responds with a job_l D.

[0079] In step 107, the computer 104 starts and executes self-tests. A signature manifest, which describes all files necessary for starting up the system from storage partition 1 , is retrieved in step 108 by the firmware in the computer 104.

[0080] In step 109, the computer 104 determines that all files are correct 1 10. A calculated hash is compared with the decrypted hash for files listed in the signature manifest.

[0081] If it is verified in step 1 10 that all hashes match, execution of the installer mage begins in step 1 1 1. Afterwards, in step 1 12, time synchronization occurs.

[0082] In step 1 13, a request with current time and a reference to slot 1 in the identity compartment returns a passkey. Slot 1 in the identity compartment holds the identity secret for Operatori . In step 1 14, the computer presents the passcode from step 1 13 to Operatori , and in return in step 1 15 receives the handover secret together with the URL to Operator2. In step 1 16, the handover secret is stored in the handover compartment of the secret manager. In step 117, the current time and the handover secret are used to calculate a new passkey which is submitted to Operator2, 101. Upon success, Operator2 in step 118 returns OP2_integrity_secret.

[0083] In step 119, OP2_integrity_secret is stored in multiple slots, corresponding to all logical storage partitions for Operator2.

[0084] The sequence continues in Fig. 1 b with step 120, where the handover secret and time are used to generate a passkey. In step 121 , serial number and passkey are sent to Operator2. The response is a new installer image (installjmage) and the encrypted hash of the image (signature).

[0085] Steps 122 and 123 verify the integrity of the received installer image. Upon success, the installer image is in step 124 installed to storage partitions 3 and 4. Step 125 sets the default boot storage partition to 3. Step 126 reboots the computer 104.

[0086] The sequence continues in Fig. 1 c with steps 127 to 131 , loading the signature manifest and verifying the installed files against the integrity secret stored in slot 3 of the integrity compartment. Step 132 generates a new passkey, which in step 133 is submitted to Operator2, together with the serial number of the computer 104, to indicate that the handover has succeeded. The response 134 from Operator2 includes OP2_identity_secret. In step 135, Operator2 may notify Operatori about the completion of the handover.

[0087] In step 136, the new identity secret is stored in slot 2 of the identity compartment (the use counter for this secret is also set). In step 137, the handover secret stored in the handover compartment is deleted. The computer is now handed over to Operator2, and the installation of the payload image can be executed.

[0088] The sequence continues in Fig. 1d with Step 138, where the handover secret and time are used to generate a passkey. In step 139, serial number and passkey are sent to Operator2. The response is a payload image (payloadjmage) and the encrypted hash of the image (signature).

[0089] Steps 140 and 141 verify the integrity of the received payload image. Upon success, the payload image is installed 142 to storage partition 5 and 6. Step 143 sets the default storage partition to 5. Step 144 reboots the computer 104.

[0090] The sequence continues in Fig. 1 e, which is a sequence diagram illustrating the components involved in the boot sequence, continuing from Fig. 1 d and the reboot event 144. In step 149, the signature manifest (905 in Figs. 9a-c below) is loaded, and in step 150, it is stored in RAM 145. In step 151 , the signature (909 in Figs. 9a-c below) is loaded. In step 152, the signature and the calculated hash value of the signature manifest are transmitted to the secret manager 105. Prior to this, the default storage partition has been set to slot 5 (step 142 in Fig. 1d). Within the integrity compartment of the secret manager 105, the corresponding integrity secret for storage partition 5 is stored. This secret is used to decrypt the signature and compare the decrypted value with the calculated hash value of the signature manifest. The decryption and comparison are performed entirely within the secret manager 105.

[0091] The manifest stored in RAM 145 is then used to load all files required for executing payload phase 1 , 147. Each loaded file is integrity-checked by calculating its hash and comparing it with the corresponding hash entry in the signature manifest, as shown in steps 153 and 154. In step 155, slot 2 is activated within the identity compartment of the secret manager 105. Before control of the computer 104 is transferred from firmware 146 to payload phase 1 , 147, in step 156, a watchdog is enabled (711 in Fig. 7b below), and slot 5 in the integrity compartment of the secret manager 105 is set to unavailable (712 in Fig. 7b below). This can take place before or after step 155.

[0092] When payload phase 1 , 147, is invoked, it reads in step 157 the signature manifest stored in RAM 145 and verifies in steps 158 and 159 the integrity of all files listed therein. Upon successful verification, control is in step 160 transferred from payload phase 1 , 147, to payload phase 2, 148. When payload phase 2, 148, is initiated, the watchdog is taken over (716 in Fig. 7b below), storage partition 5 is again set to available (717 in Fig. 7b below), and execution of the payload begins (718 in Fig. 7b below).

[0093] Figs. 2a-c is a sequence diagram that describes how the current Operator2, 102, transfers control of the computer back to Operatori , 201 , according to an example embodiment of the invention. In step 206, Operator2 submits the serial number of the computer 104 together with an identifier of the task (job_l D) to Operatori . The response includes a handover secret and the URL of Operatori . The handover secret is passed to the computer 104 in step 207 for storage in the handover compartment of the secret manager 105 in step 208. In step 209, services are turned off, and all data is backed up in step 210. In step 211 , default boot is set to storage partition 3, followed by reboot in step 212.

[0094] After reboot, the computer 104 in step 213 loads signature manifest from local storage base 3. All files in the signature manifest are verified by in step 214 calculating a hash value and in step 215 sending the hash value together with the encrypted hash from the signature manifest for verification using slot 3 of the integrity compartment. Upon success, the installer image from Operator2 can be executed. The sequence continues in Fig. 2b with step 216, where execution of the installer image from Operator2 starts. All data is erased in step 217. In step 218, synchronize time is executed, with the computer 104 as time source. In step 219, a passkey is created based on the handover secret, retrieved from the handover compartment of the secret manager. In step 220, passkey and serial number are submitted to Operatori , which responds with OP1_integrity_secret. In step 221 , OP1_integrity_secret is stored in the secret manager 105. In step 222, a passkey is generated. In step 223, the serial number and passkey are submitted to Operatori , which responds with an install image and a signature. In steps 224 and 225, the installer image is verified, followed by installation in storage partition 1 in step 226.

[0095] The sequence continues in Fig. 2c with step 227, where a default boot partition is set. The computer 104 then in step 228 reboots from local storage 1 . In steps 229, 230 and 231 , the install image from Operatori is verified. In steps 232 and 233, the passkey is created based on time, and the handover secret is stored in the handover compartment of the secret manager. In step 234, the computer 104 submits serial number and passkey to Operatori . The response contains a new identity secret (OP1 _identity_secret). In step 235, the new identity secret is stored, and the counter in the secret manager 105 is set to its default value. In step 236, the handover secret is deleted.

[0096] Fig. 3 shows a state diagram comprising three states. The initial state 301 represents the condition where the computer 104 has been initialized. In 304, power-on is performed, followed by loading and verification of the installer software in 305. Upon successful verification, the next step is the retrieval of the handover secret, either online via a public network connection from Operatori (see Figs. 1 a-e for the online embodiment) or offline. For offline operation, the handover secret is located in a dedicated storage partition of the physical storage media. The installer software has access to the identity secret for Operatori , which is used to decrypt the handover secret in 306. The handover secret is then in 307 used to decrypt the integrity secret for Operator2. In 308, the distribution image for the installer software signed by Operator2 is verified and installed in the computer. In 309, the computer is rebooted and an attempt is made to execute the Operator2 installer software.

[0097] If the execution fails, the computer detects this and enters failed state 303, indicating a failed handover from Operatori to Operator2, where the storage partition is marked as unavailable. The computer remains in this state for handling error 317 until the watchdog triggers and the computer reboots again. After a failed attempt, the subsequent boot avoids the previously failed storage partition. If the computer is deployed online and connected to a public network, it will, after reboot, revert to the installer software in storage partition 1 and in 317 report the failure to Operatori . When the computer reaches the operational state 302, indicating a successful handover, execution continues in 310 with the software installed by Operator2. The integrity secret used to verify the Operator2 installer software also enables access to write a new identity secret. The handover secret previously stored in 306 is in 31 1 used to decrypt the identity secret for Operator2, which is then stored in the computer in 312. The computer thus possesses both the integrity and identity secrets received from Operator2 through the handover process.

[0098] From this point onward, there is no longer any need for the handover secret; therefore, it is deleted in 313. In 314, the Operator2 distribution image containing the payload software is loaded, verified using the OP2_integrity_secret, and installed in storage partition 5. After the default boot partition is set to partition 5, the computer is rebooted again in 316. Upon successful reboot, the computer is now operational, and the handover from Operatori to Operator2 is completed

[0099] Fig. 4a illustrates the secret manager 105 (which is a part of computer 104 which can communicate securely with the rest of the computer 104). The integrity compartment 402 is the compartment for integrity secrets, used to decrypt hashes related to software images before installation or boot. The identity compartment 403 is the compartment for identity secrets. The handover compartment 404 is the compartment for the handover secrets (which may be a part of the identity compartment 403). The handover secrets may be shared by the secure element in the media, and two operators during the handover process.

[0100] The integrity compartment 402 comprises one slot for each logical storage partition in the physical storage media. Each slot in the integrity compartment 402 is configured to comprise an integrity secret to be used for verifying the integrity of the software in the storage partition.

[0101] The identity compartment 403 has two slots, each comprising an identity secret associated with an operator, to be used for verifying the identity of the operator. One of the slots is always bound to the current operator of the computer. The identity compartment 403 is configured to be initialized with an identity secret for a first trusted operator in the first slot. The first slot is only accessible by the first trusted operator, and the second slot is not accessible by the first trusted operator. The identity compartment 403 is integrated in the boot process for the logical storage partitions in the physical storage media. Logical storage partitions 1 and 2 are bound to the first trusted operator, and logical storage partitions 3-6 are bound to the current business operator.

[0102] The handover compartment 404 is configured to comprise a handover secret that is provided by the current operator, after having been distributed from the designated operator to the current operator. Each handover secret is usable only once. If all files in a logical storage partition are successfully verified, the index of the operator is known. Access to identity slots is only enabled for an operator that has passed the boot integrity check. This approach provides isolation of highly sensitive secrets in one computer being managed by multiple operators. Instead of handover between any operator, the procedure requires that Operatori is special and must always be involved in all handovers.

[0103] The above table shows how fixed and removable storage devices are abstracted into six logical storage partitions. Logical storage partitions 1-4 are installer partitions, used for installer images. The installer image must be stored in the installer partition suitable for the bootloader. In logical storage partitions 5 and 6, the payload operating system resides. To enable remote migration of the underlying operating system and keep the complexity of the bootloader low, the first payload partition in logical storage partitions 5 and 6 should preferably comply with the filesystem used in logical storage partitions 1-4. With two physical storage devices, each device must provide two installer partitions as a minimum. Operatori is responsible for installing two installer images in logical storage partitions 1 and 2. During handover, these two logical storage partitions improve availability if any problem occurs. When Operator2 has installed images in logical storage partitions 3 and 4, the handover is completed, and the installation of the payload operating system in logical storage partitions 5 and 6 can be performed.

[0104] An example of the deployment is provided in the table below. An example of a filesystem that can be easily implemented in ROM code is provided below.

[0105] / dev / mmcblk0p4 6144000 62514175 56370176 29GB 83 Linux

[0106] / dev / sda1 8192 2047999 2048000 1GB c W95 FAT32 (LBA)

[0107] / dev / sda2 2048000 4095999 2048000 1GB c W95 FAT32 (LBA)

[0108] / dev / sda3 4096000 6143999 2048000 1GB c W95 FAT32 (LBA)

[0109] / dev / sda4 6144000 62514175 56370176 29GB 83 Linux

[0110] For computers with hypervisors, additional secrets may be required for each slot. A level parameter may be used to divide each slot into sub slots. The operating system has level 1 , and the underlying hypervisor may have level 2. All secrets related to Operatori are activated during factory reset, therefore they cannot be removed, just disabled, enabled or replaced by Operatori (see Fig. 2). These secrets, indexed as fixed, could be stored by Operatori and not the manufacturer, if they are separate entities. When the computer is managed by Operatori , the secrets could be overwritten, enabling secret rotation.

[0111] All algorithms in firmware are symmetric, and therefore less vulnerable to known quantum attacks. The secret manager 105 depends on strong isolation, and must be implemented as a secure element isolated from the normal execution environment in the computer. Each compartment keeps secrets in slots. To avoid attacks against the secrets, a counter is preferably set to a default value when the secret is stored and decremented for each use.

[0112] Fig. 4b illustrates how availability and failsafe handover requirements between operators map to storage partitions. The use of two physical storage units, which may consist of either fixed or removable media, ensures basic availability. As long as one storage unit is functional, computer 104 remains operational.

[0113] Software updates are necessary to introduce new functionality and apply security patches. Recent regulations for electronic products with software impose additional requirements. To ensure resilience against power interruptions during updates, the operating system is deployed in installer and payload partitions. The installer image loads into volatile memory from the installer partition before execution. During execution, the installer retrieves the distribution image, verifies its integrity, and installs the software into another partition. If a power failure occurs, the installer remains unaffected since the software in the installer partition is never modified. The last file written to the target storage partition is the digital signature, which verifies the integrity of the signature manifest.

[0114] The payload software installs twice, once in each of the two separate storage partitions, and the same redundancy applies to the installer software. During the handover of computer 104 between operators, two additional installer partitions are required, resulting in a total of six partitions, numbered from 1 to 6. The firmware monitors the availability of these partitions. To avoid inconsistency, each storage partition is assigned a priority when both are available. The firmware enforces isolation between partitions to ensure that installation remains within partition boundaries.

[0115] Fig. 5 illustrates the restoring of a computer 104 to factory settings. This sequence is not dependent on accurate time or network connection. The result of a factory reset includes the deletion of all images and secrets from any other operator than Operatori . When the computer boots and detects a factory reset request in step 506 (holding a button during power on), it selects in step 507 only images from storage partitions 1 and 2. All secrets related to Operator2 are removed in steps 508 and 509. Upon successful verification of integrity in steps 510, 511 , 512, and execution of the installer image in step 513, all data in storage partitions 3-6 is erased in step 514. Before reboot in step 516, the default boot is set to storage partition 1 in step 515. From now on, a standard installation process for deployment applies (see Fig. 1).

[0116] The delete operation for identity slot 2 is allowed, but not any other operation such as generating passkeys, since this procedure is executed by software verified as Operatori .

[0117] Fig. 6 illustrates how an operator can change a secret in a computer 104. The three actors are the current operator, Operator2 102, the computer itself 104, and the secret manager 105. All secrets originate from the current operator 102, where the initial trust root for identity and integrity is established. In step 606, the current operator submits a store secret request with a passkey based on the current identity secret to computer 104. In step 607, time is retrieved from the computer 104. In step 608, the expected result should match the received passkey from Operator2. If the two passkeys match, a new_OP2_identity_secret is in step 609 sent from the computer 104, to be written to slot 2 in the identity compartment 403 in step 610, and the counter is set to its default value in step 611. The secret manager 105 may in step 612 confirm to the computer 104 that OP2_identity_secret has been updated. The computer 104 may in step 613 confirm to Operator2 that OP2_identity_secret has been updated.

[0118] It is not possible for any operator to update secrets associated with another operator. Figs. 7a-b is a flowchart describing high-level logic in boot loading, starting at 701 with power on self-test. At 702, the computer’s firmware checks if the reset button has been pressed (this is only necessary for offline operation). If factory reset has been requested, 703 returns the computer 104 to the factory state (as illustrated in Fig. 5). If factory reset has not been requested, the computer’s firmware checks for the default storage partition in 704. If it exists, manifest and files are loaded in 705, and all files required for boot are verified in 706. If there is no default storage partition, the firmware enumerates all storage partitions in priority order (e.g. using the prioritized list), and checks for availability in step 707. Manifest and files from the selected storage partition are loaded in 708, and all files required for boot are verified in 709. If the verification fails, the next storage partition on the prioritized list is selected in 710.

[0119] Fig. 7b continues the flowchart when the verification succeeds in either 706 or 709. A watchdog is enabled in 711. In 712, the storage partition is set to unavailable. In 713, the identity slot is used to enable access for the operating system to operate on identity secrets, however any access to the other operator is excluded. For example, if the storage partition is storage partition 1 , slot 1 in the identity compartment 403 is enabled, and slot 2 is disabled, and if the storage partition is storage partition 3, slot 2 in the identity compartment 403 is enabled, and slot 1 is disabled. Control of the identity takes place prior to boot, and this ensures complete isolation between the operators.

[0120] In step 714, the computer boots. Upon failure (typically because of watchdog timeout), reset 715 brings the computer back to 702, with the storage partition still set to unavailable (which means that the failing installer partition is excluded from the prioritized list). Upon success, the operating system takes over management of the watchdog in 716, and the storage partition is again set to available in 717 (which means that the storage partition will again be on the prioritized list). In 718, execution of the installer or payload continues.

[0121] Figs. 8a-d describe scalability aspects of the key distribution. With asymmetric algorithms such as RSA and ECDSA, the same public key can be deployed to many computers. With certificate chains, different signers with unique private keys can be deployed in a hierarchy, with only the top-level public key being distributed to all computers. With symmetric keys, the same secret / key is used for both encryption and decryption, without any hierarchy. The drawback of RSA and ECDSA is the vulnerability for attacks with future quantum computers. Signing and verification are the foundation of software integrity, which is based on hash and encryption.

[0122] Fig. 8a illustrates an embodiment comprising two cryptographic systems. In Fig. 8a, 801 represents a system in which two computers 104 each possess a unique pair of cryptographic secrets, which are symmetric. One key is used internally within the computer, and a corresponding key is used externally. The symmetric approach provides limited scalability in key distribution; however, it offers advantages in terms of resilience against post-quantum attacks. Another advantage of symmetric cryptographic algorithms is the reduced key and implementation size, which makes them suitable for integration in firmware.

[0123] In Fig. 8a, 802 illustrates an asymmetric cryptographic system. In this embodiment, each computer uses a pair consisting of a private key and a public key. Asymmetric systems enable scalable key distribution; however, maintaining resilience against post-quantum attacks requires the use of updated algorithms and longer keys, which increases implementation complexity in firmware-based environments.

[0124] Fig. 8b illustrates an embodiment of a hybrid key-distribution system that enables implementation in constrained environments while providing post-quantum resilience. In Fig. 8b, 806 designates a bounded region, represented by a dotted line, indicating a trusted environment. Within this trusted environment 806, a symmetric key may be both generated and stored at Operator, 101 , and within the secret manager 105. Key distribution is not a problem, since the integrity secret for Operatori is stored in proximity to the computer 104 in a trusted environment. When the computer 104 is produced, all computers initially share the same secret. Consequently, the factory software 811 may be executed on all computers.

[0125] When the secrets are subsequently replaced in the secret manager 105, and the operational software is installed in installer partitions 1 and 2 (see Fig. 4b), the computer 104 becomes ready for deployment. The factory software 811 also includes configuration data describing how the physical storage is divided into storage partitions (see Fig. 4b), thereby ensuring isolation between storage areas.

[0126] In Fig. 8b, 808 represents a public network that may include potential adversaries capable of postquantum attacks. 809 represents the computer 104 in operation, including a secret manager 105 and operational software 812. The software contains a public key designed to be resilient against post-quantum attacks.

[0127] In Fig. 8b, 807 represents Operator2, 102, which possesses two keys. The key on the right corresponds to the private key associated with the post-quantum-resilient public key contained in 809. These two keys form part of a scalable public-key infrastructure, wherein all operational software 812 includes the same public key.

[0128] When a secure communication channel has been established between 809 and 807, a new secret may be transferred from 807 to the secret manager 105, e.g. over post quantum resilient algorithms implemented in the installer image from Operatori executing in 809. Prior to storing the new identity secret, the previous identity secret may be used to authenticate the computer 104 towards Operator2. The operating system may contain other methods of authentication that could be used in parallel with the authentication described here.

[0129] In Fig. 8c, software image 810 represents an image where both the operator and the computer calculates a hash. The operator encrypts the hash 811 using a secret 812, and the computer decrypts the hash using the same secret 812. If the calculated hash matches the decrypted hash, the computer assumes that the image has not been tampered with during transit. Signature and verification can be implemented with both asymmetric and symmetric algorithms.

[0130] In Fig. 8d, 803 represents the initial state of the computer, with secrets and installer images from Operatori . To achieve availability, there are images on both fixed and removable storage. During handover 804 from Operatori to Operator2, there is a critical moment where the two images from Operatori provides fallback. 805 represents the computer managed by Operator2, with two installer images and two payload images being deployed. To support factory reset of the computer, the two installer images in slots 1 and 2 are still present. The dotted box represents the secret manager 105, which receives both the calculated and the encrypted hash as input. The output is not the decrypted data, just passed or failed. This approach minimises leak of data that could be used in attacks.

[0131] Figs. 9a-c illustrate methods for creating distribution images for the computer 104.

[0132] Fig. 9a depicts a configuration based on a standard Linux distribution, such as Ubuntu. The only requirement concerns the layout of the storage 904 - the first partition must conform to the format required by the computer’s firmware implementation (VFAT). The install configuration 902 defines parameters that make the computer 104 unique. Using this configuration, the necessary files are selected from the standard operating system 901 together with parameters specific to the target hardware, which controls the installation 903. A signature manifest 905 may be manually created and restricted to the most critical files. This process serves to prototype and adapt a new operating system image

[0133] Fig. 9b illustrates a fully automated system for generating distribution images 908 tailored for individual computers 104. A customized operating system 910 is adapted to match the storage layout. This may be performed automatically using build frameworks such as Buildroot or Yocto, or through an air-gapped build process from vetted source code to enhance security. Under forthcoming regulatory frameworks, the signature manifest 905 may serve as verifiable evidence of compliance. This approach favors the release of well-defined, monolithic builds over incremental patches, improving security by simplifying hardening and enabling more comprehensive testing.

[0134] All files used in the custom configuration 91 1 are included in the signature manifest 905. Regulatory requirements may mandate providing a complete list of software components. The computer configuration 912 generates all files containing device-specific settings for computer 104 and appends them to the signature manifest 905.

[0135] The software release 906, common to Figs. 9a and 9b, involves adding the signature manifest 905 (containing hash values of each file) to the distribution image 908. The hash value of the signature manifest 905 is computed and encrypted using the integrity secret 907, and the encrypted result is appended to the distribution image 908 (which may contain both installer image and payload image). In the final release stage, the complete distribution image 908 is itself hashed, and the result is encrypted with the integrity secret 907 to produce the signature 909.

[0136] Fig. 9c demonstrates how integrity control is integrated into the software build process. When the storage partition 904 is formatted, it is divided into two filesystems: a first filesystem 913 (VFAT), compatible with firmware 146, and a second filesystem 914 (CustomFS), adapted for the payload software supported by payload phase 1 , 147. The signature manifest 905 includes a section 915 listing files and corresponding hash values used to verify the integrity of files in the CustomFS 914 before control of the computer 104 is transferred to payload phase 2, 148.

[0137] The below table is an example of a signature manifest that specifies the partitions required for an image in a storage partition. This type of metadata is often used to integrate software build with product management. With symmetric keys / secrets, all images must have individual signatures corresponding to the verification in the target (computer). Regardless of manual or automated build, the result complies to the format described. For rapid prototyping, manual build is preferred, but for production, embedded should be considered.

[0138] In the above table, each row represents one of the six different storage partitions. The first column is the storage partition index. The second column is the status, indicating whether the storage partition is available or unavailable for loading images. There is also a flag for default, meaning that if there are multiple available options, default is the first option. The third column is the priority, for example if one wants to boot from external media before internal media. The fourth column indicates which device it points to: either internal flash memory (referring to persistent storage), SD card, or MMC. The other option is SDA, which refers to USB stick or removable storage. For each media type, there can be up to two partitions. There must be a Boot partition which can be read by firmware, and this should typically be VFAT32. The Root partition is assigned for the payload operating. The last column is the identity slot that controls access based on storage partition index. This provides strong isolation between different operators.

[0139] In the examples above, handover occurs between Operatori and Operator2, but it may involve any number of operators, as long as control of computer 104 is first transferred to Operatori . For products intended for general consumer use, this allows computer 104 to be owned by the end user, while still permitting operator changes. In this way, costly installations can be avoided when computer 104 is connected to an end user’s energy system, which would otherwise require service by a certified electrician.

[0140] Fig. 10 illustrates a sequence diagram in which a manufacturer, Operatori , 101 , provides isolation between two business operators, a civil operator 1001 and a defense operator 1002. Since the disclosed concept supports both offline and online operation, it could be deployed as part of drone. For agricultural applications, the drone could e.g. distribute fertilizer on low altitudes, for military applications, the drone could e.g. carry explosives. Experience from modern drone operations demonstrates the advantage of enabling dual-use systems through civilian applications such as aerial forestry fertilization. In the event of war, the drones can be equipped with alternative payloads and be reassigned to a new operator. This enables technology reuse at high volume and low cost.

[0141] In Fig. 10, a civil operator 1001 in step 1006 orders a drone equipped with computer 104 and, upon delivery, in step 1007 receives its civil distribution image installed. Step 1008 illustrates civil operation. In the event of military activation, the defense operator 1002 requests control of computer 104, resulting in handover from civil operator 1001 to Operatori , 101 , in steps 1009 and 1010. In steps 101 1 and 1012, handover takes place from Operatori to defense operator 1002. Step 1013 illustrates defense operation.

[0142] If computer 104 controls a drone, the drone may also be shared among additional operators contributing to functions such as forest-fire suppression. During civil operation, the drones can collect terrain data later used for navigation, providing an operational advantage when similar data quality is unavailable to other actors. The disclosed concept does not rely on continuous radio communication, thereby reducing vulnerability to interference.

[0143] Adversaries that attack computers via logic access often stay silent for a long period in order to learn about the victim’s infrastructure. After stealing data, the intruder encrypts backup, and finally destroys production data. By reinstalling the payload operating system on a scheduled basis, with different versions of the operating system, it is very hard for any ransomware to persist. This procedure involves two handovers, which include a complete erase of data from the current operator (including any ransomware). Monitoring of the handover combined with verification of backup data is also good practice that could be integrated into this procedure.

[0144] An arrangement for allowing handover of a computer 104 between a current and a designated operator is thus provided. The computer 104 preferably comprises: first and second physical storage media, each physical storage medium comprising at least three different logical storage partitions on which different types of operating systems may be remotely installed: two installer partitions, each configured to contain an installer version of an operating system, and one payload partition, configured to contain a payload operating system; a read-only memory comprising firmware for the computer boot process, the read-only memory being arranged to load the operating system; and a secret manager 105, comprising an integrity compartment 402, an identity compartment 403, and a handover compartment 404. The integrity compartment 402 preferably comprises one slot for each logical storage partition in the physical storage media, each slot configured to comprise an integrity secret to be used for verifying the integrity of the software in the storage partition. The identity compartment 403 preferably comprises first and second slots, each configured to comprise an identity secret associated with an operator, to be used for verifying the identity of the operator, and is preferably configured to be initialized with an identity secret for a first operator 101 in the first slot, where the first slot is only accessible by the first operator 101 , and the second slot is not accessible by the first operator 101 . The handover compartment 404 is preferably configured to comprise a handover secret that is entered by the current operator, after having been distributed from the designated operator to the current operator. The handover of the computer 104 from a current to a designated operator is preferably configured to always use the handover secret in the handover compartment 404 of the secret manager 105, which handover secret is usable only once. Either the current or the designated operator must be the first operator.

[0145] This enables handover between different operators to be made via a trusted first operator 101 , by the current operator first handing over to the trusted first operator 101 , and the trusted first operator 101 then handing over to the new operator.

[0146] In embodiments, the first operator 101 is the manufacturer of the computer 104. Other operators are typically business operators.

[0147] In embodiments, the arrangement is configured to use a prioritized list in order to select one of the four installer partitions to be used for loading the operating system, the prioritized list defining an order of prioritization for the four installer partitions.

[0148] In embodiments, the arrangement comprises a watchdog unit, arranged to detect failed attempts to load the operating system from a given logical storage partition, wherein upon a failed attempt, the failing installer partition is excluded from the prioritized list.

[0149] In embodiments, the first physical storage medium is a fixed storage medium and the second physical storage medium is an exchangeable removable storage medium.

[0150] In embodiments, the arrangement comprises a signature manifest 905 in each logical storage partition, which signature manifest 905 is arranged to enable integrity verification in order to cryptographically protect files located in the logical storage partition against tampering.

[0151] In embodiments, the integrity secrets, the identity secrets and the handover secrets in the secret manager 105 are based only on symmetric algorithms and / or one-way hash functions, so that verification may be performed by providing both the received and encrypted hash sum and the calculated hash sum as input, returning a result of the operation as a minimal binary verdict. This makes the arrangement quantum resistant.

[0152] In embodiments, some secrets in the secret manager 105 are arranged to be replaceable by the current operator when they have been used a predetermined number of times. This increases the security of the arrangement.

[0153] In embodiments, the computer 104 is arranged to be restorable so that the first operator 101 becomes the current operator by activating a reset, causing the installation image of the operating system to erase all data. This enables a safe factory reset of the computer 104. Figs. 11a-c illustrate a sequence diagram showing the handover procedure between two operators when a computer 104 is not connected to a network. The solution separates encrypted data and cryptographic keys through manual ordering and installation procedures performed via physical removable storage.

[0154] The sequence diagram in Fig. 11 a comprises three actors: Manufacturer / Operatorl 101 , Operator2 102, which will assume control of the computer, and the customer 1101. The process begins when the customer 1101 orders a computer 104 from Operatori , 101 , in step 1102. After delivery, the customer requests in step 1103 that Operator2, 102, shall take over control of the computer 104. In step 1104, Operator2, 102, generates a handover secret. In step 1105, the handover secret is transmitted to Operatori , 101. In step 1106, the handover secret is encrypted using the identity secret that already exists in the computer 104 (this identity secret was created when the computer 104 was initialized). In step 1107, an identity secret unique to the computer 104 is generated. In step 1108, an integrity secret, also unique to the computer 104, is generated. In step 1109, the secrets from steps 1107 and 1108 are encrypted with the handover secret. In step 1110, checksums protecting the distribution images are encrypted with Operator’s integrity secret. In step 1111 , the results from steps 1106, 1109 and 1110 are prepared for transfer. In step 1112, these data are manually written to removable physical storage.

[0155] The sequence diagram in Fig. 11 b comprises two actors: computer 104 on the left and secret manager 105 on the right. In step 1113, the removable physical media received from Operatori , 101 , is connected to the computer 104. In step 1114, the computer 104 boots and loads the installer software from its storage partition. In step 1115, the installer software detects the removable media and locates the handover secret encrypted with the identity secret of Operatori . Because the installer software is issued by Operatori , the computer can decrypt the handover secret and install it into the secret manager 105. In step 1116, the handover secret is used to decrypt the integrity secret of Operator2, which is then added to the secret manager 105. In step 1117, software is installed into storage partition 3 after verification using Operator’s integrity secret. In step 1118, storage partition 3 is set as the default boot partition, and in step 1119 the computer 104 is restarted.

[0156] The sequence diagram in Fig. 11 c comprises the same two actors as Fig. 11 b: computer 104 and secret manager 105. After the installer software has been verified and begins execution, the O P2_identity_secret, which was encrypted with the handover secret, is decrypted and added to the secret manager 105. Access control within the integrity subsystem ensures that identity secrets of Operatori and Operator2 are mutually exclusive. In step 1120, the handover secret is no longer needed and therefore deleted. In step 1 121 , payload software from Operator2 is installed into storage partition 5. The source of this software is the removable physical storage, which includes an additional partition beyond those previously mentioned. Before installation, the software is verified through signature validation. This extra partition allows subsequent installations also in partitions 4 and 6 on the same removable storage. After installation, in step 1 122 the computer 104 is instructed to boot primarily from storage partition 5. After reboot in step 1 123, the computer 104 has been successfully transferred to Operator2, 102, and now executes payload software issued by Operator2.

[0157] Fig. 12 schematically illustrates a method 1200 for allowing handover of a computer 104 between a current and a designated operator, the computer 104 comprising: first and second physical storage media, each physical storage medium comprising at least three different logical storage partitions on which different types of operating systems may be remotely installed: two installer partitions, each configured to contain an installer version of an operating system, and one payload partition, configured to contain a payload operating system; a read-only memory comprising firmware for the computer boot process, the read-only memory being arranged to load the operating system; and a secret manager 105, comprising an integrity compartment 402, an identity compartment 403, and a handover compartment 404. The method 1200 comprises:

[0158] Step 1210: configuring the integrity compartment 402 to comprise one slot for each logical storage partition in the physical storage media, each slot comprising an integrity secret to be used for verifying the integrity of the software in the storage partition.

[0159] Step 1215: configuring the identity compartment 403 to comprise first and second slots, each comprising an identity secret associated with an operator, to be used for verifying the identity of the operator.

[0160] Step 1240: initializing the identity compartment 403 with an identity secret for a first operator 101 in the first slot, which identity secret can never be removed from the first slot, where the first slot is only accessible by the first operator 101 , and the second slot is not accessible by the first operator 101 .

[0161] Step 1250: distributing a handover secret from the designated operator to the current operator.

[0162] Step 1260: providing, by the current operator, the handover secret to the computer 104, for entering into the handover compartment 404. Step 1270: effecting handover of the computer 104 from the current to the designated operator using the handover secret, which handover secret is usable only once, wherein either the current or the designated operator must be the first operator 101.

[0163] This enables handover between different operators to be made via a trusted first operator 101 , by the current operator first handing over to the trusted first operator 101 , and the trusted first operator 101 then handing over to the new operator.

[0164] The above steps may be effected in any order that makes technical sense, and some of the steps may be effected simultaneously with each other.

[0165] In embodiments, the first operator 101 is the manufacturer of the computer 104. Other operators are typically business operators.

[0166] The method 1200 may further comprise one or more of:

[0167] Step 1220: arranging the integrity secrets, the identity secrets and the handover secrets in the secret manager 105 to be based only on symmetric algorithms and / or one-way hash functions, so that verification may be performed by providing both the received and encrypted hash sum and the calculated hash sum as input, returning a result of the operation as a minimal binary verdict. This makes the method quantum resistant.

[0168] Step 1225: arranging some secrets in the secret manager 105 to be replaceable by the current operator when they have been used a predetermined number of times.

[0169] Step 1230: arranging the computer 104 to be restorable so that the first operator 101 becomes the current operator by activating a reset, causing the installation image of the operating system to erase all data. This enables a safe factory reset of the computer 104.

[0170] Step 1275: using a prioritized list in order to select one of the four installer partitions to be used for loading the operating system, the prioritized list defining an order of prioritization for the four installer partitions.

[0171] Step 1280: using a watchdog unit to detect failed attempts to load the operating system from a given logical storage partition.

[0172] Step 1285: upon a failed attempt, excluding the failing logical storage partition from the prioritized list. Step 1290: using a signature manifest 905 in each logical storage partition to enable integrity verification in order to cryptographically protect files located in the logical storage partition against tampering.

[0173] The above steps may be effected in any order that makes technical sense, and some of the steps may be effected simultaneously with each other.

[0174] The foregoing disclosure is not intended to limit the present invention to the precise forms or particular fields of use disclosed. It is contemplated that various alternate embodiments and / or modifications to the present invention, whether explicitly described or implied herein, are possible in light of the disclosure. Accordingly, the scope of the invention is defined only by the claims.

[0175] TERMINOLOGY

[0176] The following exemplifies how some of the terminology used in this disclosure could be explained.

[0177] Computer: The term “computer” refers to an embedded computing unit comprising at least one central processing unit (CPU), random access memory (RAM), and non-volatile memory (ROM or flash memory) containing firmware. The computer is designed to operate autonomously without the need for a user interface, such as a display or keyboard. It further comprises at least two physical storage devices or partitions used for persistent data and executable code. At least one of the storage devices may be removable, for example a USB memory device used for data exchange, firmware updates, or secure key storage. The computer may include communication interfaces for connecting to external systems or networks, but does not require any human-machine interaction during normal operation

[0178] Computer configuration: Defines unique parameters for the “computer”, as well as the list of all files and their hash values to be included in the “signature manifest”.

[0179] CustomFS: A file system within a partition that is readable by the second software executed at reset / start - either the “installer” or the first stage of the “payload”.

[0180] CustomFS list: List of all files, including hashes, to be verified when the “computer” starts. Integrity check is performed when “payload phase 1” executes. If everything is valid, control is passed to “payload phase 2”.

[0181] Custom configuration: Software that, based on a “computer configuration”, installs “software” and also generates a “signature manifest”. Custom operating system: “Software” that is customized and where all components are likely installed.

[0182] Distribution image: A format, e.g., ISO 9660, suitable for distribution and installation on a “computer”.

[0183] Firmware: Software that is an integral part of the “computer” and executes immediately after power- on / reset.

[0184] Handover secret: The term “handover secret” refers to a symmetric cryptographic secret / key used to securely transfer operational control of a computer between two operators. The handover secret is stored within a dedicated compartment of the secret manager and is used by the installer software. Before the payload software is installed, the handover secret is deleted to prevent its use after handover. During the handover process, the handover secret is used to install both the integrity and identity secrets associated with the operator that is taking over control of the computer. The handover secret can be exchanged and verified regardless of whether the computer is connected to a public network or operates in an isolated (stand-alone) mode

[0185] Installation: Standard software that installs “software” based on an “install configuration”.

[0186] Install configuration: Defines which packages from the “standard operating system” shall be installed in the “storage partition” as well as unique parameters for the “computer”.

[0187] Integrity secret: A symmetric secret / key, unique for each “computer”, used to encrypt a hash which constitutes a “signature”.

[0188] Operator: The operator is responsible for maintaining and delivering the payload software that adds commercial value to the computer, typically installed as part of a system. The operator manages all software in the computer throughout its entire lifecycle, including the secure transfer of control of the computer to a new operator.

[0189] Physical storage: Physical storage component such as solid state drive (SSD) or USB-stick.

[0190] Signature: A signature consists of a hash of a file, which is then encrypted. When verifying a signature, the receiver obtains both the file and the encrypted hash.

[0191] Signature manifest: A format in which all files to be verified for integrity are listed. Signature (manifest file): This file protects the “signature manifest” from tampering. The “firmware” first loads the “signature manifest” and computes its hash. The “signature” is then decrypted and compared with the calculated hash.

[0192] Software: “Software” refers to the content inside a distribution image. Software release: Process step where the “signature manifest” is included in the “distribution image” together with a signature. Finally, a “signature” is also created for the “distribution image”.

[0193] Standard operating system: “Software” that is part of a standard operating system where only a subset of packages is installed. Which packages are installed is defined in the “install configuration”. Storage partition: A portion of the physical storage, divided into logical sections. Each logical section could be divided into partitions, each partition having its own file system.

[0194] Target storage partition: Refers to the storage partition in which installation of the software is to take place when an installer is executed.

[0195] VFAT: A file system within a partition that is readable by the first software executed at reset / start (“firmware”).

[0196] VFAT list: List of all files, including hashes, to be verified when the “computer” starts. Integrity check is performed when “firmware” executes. If everything is valid, control is passed to “payload phase 1”.

Claims

AMENDED CLAIMS received by the International Bureau on 30 JAN 2026 (30.01.2026)1. Arrangement for allowing handover of a computer (104) between a current and a designated operator, the computer (104) comprising: first and second physical storage media, each physical storage medium comprising at least three different logical storage partitions on which different types of operating systems may be remotely installed: two installer partitions, each configured to contain an installer version of an operating system, and one payload partition, configured to contain a payload operating system; a read-only memory comprising firmware for the computer boot process, the read-only memory being arranged to load the operating system; and a secret manager (105), comprising an integrity compartment (402), an identity compartment (403), and a handover compartment (404), wherein: the integrity compartment (402) comprises one slot for each logical storage partition in the physical storage media, each slot configured to comprise an integrity secret to be used for verifying the integrity of the software in the storage partition; the identity compartment (403) comprises first and second slots, each configured to comprise an identity secret associated with an operator, to be used for verifying the identity of the operator, and is configured to be initialized with an identity secret for a first operator (101) in the first slot, where the first slot is only accessible by the first operator (101), and the second slot is not accessible by the first operator (101); and the handover compartment (404) is configured to comprise a handover secret that is provided by the current operator to the computer (104), after having been distributed from the designated operator to the current operator, wherein the handover of the computer (104) from a current to a designated operator is configured to always use the handover secret in the handover compartment (404) of the secret manager (105), which handover secret is usable only once, and wherein either the current or the designated operator must be the first operator (101).

2. Arrangement according to claim 1 , wherein the first operator (101) is the manufacturer of the computer (104).

3. Arrangement according to claim 1 or 2, configured to use a prioritized list in order to select one of the four installer partitions to be used for loading the operating system, the prioritized list defining an order of prioritization for the four installer partitions.

4. Arrangement according to claim 3, comprising a watchdog unit, arranged to detect failed attempts to load the operating system from a given logical storage partition, wherein upon a failed attempt, the failing installer partition is excluded from the prioritized list.

5. Arrangement according to one of claims 1-4, wherein the first physical storage medium is a fixed storage medium and the second physical storage medium is an exchangeable removable storage medium.

6. Arrangement according to any one of claims 1-5, comprising a signature manifest (905) in each logical storage partition, which signature manifest (905) is arranged to enable integrity verification in order to cryptographically protect files located in the logical storage partition against tampering.

7. Arrangement according to any one of claims 1-6, wherein the integrity secrets, the identity secrets and the handover secrets in the secret manager (105) are based only on symmetric algorithms and / or one-way hash functions, so that verification may be performed by providing both the received and encrypted hash sum and the calculated hash sum as input, returning a result of the operation as a minimal binary verdict.

8. Arrangement according to any one of claims 1-7, wherein some secrets in the secret manager (105) are arranged to be replaceable by the current operator when they have been used a predetermined number of times.

9. Arrangement according to any one of claims 1-8, wherein the computer (104) is arranged to be restorable so that the first operator (101) becomes the current operator by activating a reset, causing the installation image of the operating system to erase all data.

10. Method (1200) for allowing handover of a computer (104) between a current and a designated operator, the computer (104) comprising: first and second physical storage media, each physical storage medium comprising at least three different logical storage partitions on which different types of operating systems may beremotely installed: two installer partitions, each configured to contain an installer version of an operating system, and one payload partition, configured to contain a payload operating system; a read-only memory comprising firmware for the computer boot process, the read-only memory being arranged to load the operating system; and a secret manager (105), comprising an integrity compartment (402), an identity compartment (403), and a handover compartment (404); the method (1200) comprising: configuring (1210) the integrity compartment (402) to comprise one slot for each logical storage partition in the physical storage media, each slot comprising an integrity secret to be used for verifying the integrity of the software in the storage partition; configuring (1215) the identity compartment (403) to comprise first and second slots, each comprising an identity secret associated with an operator, to be used for verifying the identity of the operator; initializing (1240) the identity compartment (403) with an identity secret for a first operator (101) in the first slot, which identity secret can never be removed from the first slot, where the first slot is only accessible by the first operator (101), and the second slot is not accessible by the first operator (101); distributing (1250) a handover secret from the designated operator to the current operator; providing (1260), by the current operator, a handover secret to the computer (104), for entering into the handover compartment (404); ensuring that the handover secret is usable only once; and effecting (1270) handover of the computer (104) from the current to the designated operator, wherein either the current or the designated operator must be the first operator (101), using the handover secret.

11. Method (1200) according to claim 10, further comprising using (1275) a prioritized list in order to select one of the four installer partitions to be used for loading the operating system, the prioritized list defining an order of prioritization for the four installer partitions.

12. Method (1200) according to claim 11 , further comprising using (1280) a watchdog unit to detect failed attempts to load the operating system from a given logical storage partition, and upon a failed attempt, excluding (1285) the failing logical storage partition from the prioritized list.

13. Method (1200) according to any one of claims 10-12, further comprising using (1290) a signature manifest (905) in each logical storage partition to enable integrity verification in order to cryptographically protect files located in the logical storage partition against tampering.

14. Method (1200) according to any one of claims 10-13, further comprising arranging (1220) the integrity secrets, the identity secrets and the handover secrets in the secret manager (105) to be based only on symmetric algorithms and / or one-way hash functions, so that verification may be performed by providing both the received and encrypted hash sum and the calculated hash sum as input, returning a result of the operation as a minimal binary verdict.

15. Method (1200) according to any one of claims 10-14, further comprising arranging (1225) some secrets in the secret manager (105) to be replaceable by the current operator when they have been used a predetermined number of times.

16. Method (1200) according to any one of claims 10-15, further comprising arranging (1230) the computer (104) to be restorable so that the first operator (101) becomes the current operator by activating a reset, causing the installation image of the operating system to erase all data.

Images