Optical Signal Encryption via Continuous Analogue Waveforms
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Solution Overview
Problem
Current optical communications systems lack effective physical layer security, as intercepted analogue signals can be easily converted back into digital form for cryptanalysis, especially in high-rate transmissions where storage and processing of analogue signals become cumbersome due to noise and dispersion.
Innovation Solution
The method involves digital signal processing to generate an encrypted optical signal with no symbol definition, using filtering and modulation to convert the signal into a continuous analogue form, making it difficult for eavesdroppers to recover the digital bit sequence, and includes chromatic dispersion compensation to mitigate transmission impairments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional intensity modulated optical transport systems transmit discrete symbols with well-defined signal levels, then the signal can be easily converted back into digital form for storage and cryptanalysis, but security is compromised
Solution Approach 1:
The patent applies parameter changes by transforming the optical signal from discrete symbol levels to continuous analogue waveforms through encryption functions. The encrypted signal varies continuously rather than maintaining fixed discrete levels, making it impossible to convert back to digital form without the encryption key. This fundamentally changes the signal parameter from discrete to continuous, achieving both security and reliable transmission.
2Ease of operation
If analogue signals are intercepted and converted to digital form for storage and processing, then cryptanalysis can be performed, but storage and processing capacity requirements increase significantly at high bit rates
Solution Approach 1:
The patent introduces an intermediary encryption function that transforms the original digital signal into an encrypted analogue waveform before optical transmission. This intermediary encrypted signal acts as a mediator that prevents direct conversion to digital form by eavesdroppers. The encryption function embeds the digital information within continuous analogue variations, requiring the specific decryption key to extract the original data, thereby avoiding the need for high-capacity analogue storage and processing.
3Reliability
If encryption is applied at multiple layers of the OSI stack, then security is enhanced, but system complexity increases
Solution Approach 1:
The patent extracts security functionality from the higher-layer OSI protocols and implements it directly at the physical layer through optical signal encryption. Instead of applying encryption at multiple layers (SONET/SDH, IPSec, TLS), the invention takes out the essential encryption function and applies it once at the optical carrier level. This single-layer physical layer encryption provides security equivalent to or exceeding multi-layer approaches while significantly reducing system complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly increases the difficulty of intercepting and decoding optical communications by requiring higher storage and processing capacity for analogue signals, providing enhanced security without significant increases in system complexity, especially in long-haul fiber optic cables.
Implementation Method 1
modulating an optical source using the encrypted electrical signal to generate a corresponding encrypted optical signal
Data Source
AI summary
A method of encrypting an optical communications signal involves determining an encryption function, filtering an electrical input signal using the encryption function to generate an encrypted electrical signal, and modulating an optical source using the encrypted electrical signal to generate a corresponding encrypted optical signal. This is then transmitted through an optical communications system. The encryption is selected such as to substantially remove symbol definition from the optical signal. This method provides digital signal processing of an electrical input signal in order to derive a signal for controlling an optical modulator in such a way that the optical signal transmitted over the link is a continuous analogue signal rather than a series of discrete symbols which alternate between well-defined signal values. This makes it difficult for a third party to derive the binary bit sequence encoded by the optical signal.