Authenticated Encryption Masking with Variable Secret Value Size
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Solution Overview
Problem
Existing authenticated encryption using a block cipher minimizes the secret value size only when the block size of a plaintext is set to b=s or b=0.5s, limiting flexibility and efficiency.
Innovation Solution
An authenticated encryption device that includes an initial processing unit to generate a secret value, a function F processing unit to update the secret value using a block cipher, and a ciphertext processing unit to perform encryption or decryption, allowing the secret value to be minimized to s+b bits even when the block size of a plaintext is set to any value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the block size of plaintext is set to specific values (b=s or b=0.5s) in existing authenticated encryption, then the secret value size is minimized, but the flexibility and efficiency are reduced
Solution Approach 1:
The patent applies dynamics by making the secret value size adaptable rather than fixed. The secret value is constructed to include a variable-length first value (derived from the key) and a second value, allowing the total size to dynamically adjust based on the plaintext block size b. This enables the system to maintain optimal secret value size s+b for any block size b, rather than requiring fixed block sizes like b=s or b=0.5s.
Solution Approach 2:
The patent changes the parameter structure of the secret value from a fixed-size conventional approach to a variable composition. The secret value is divided into two components: a first value with size varying based on the security parameter s, and a second value that adjusts based on the block size b. This parameter change allows the system to optimize secret value size while accommodating any plaintext block size, resolving the contradiction between minimizing secret value size and maintaining flexibility.
2Adaptability or versatility
If the block size of plaintext is set to any value, then the flexibility is improved, but the secret value size increases compared to existing methods
Solution Approach 1:
The patent implements a dynamic secret value construction where the size adapts to the block size parameter. The secret value consists of a first value (size determined by security parameter s) and a second value (size determined by block size b), creating a total size of s+b. This dynamic structure allows the system to accept any block size while maintaining an optimized secret value size, rather than forcing fixed block sizes that would minimize size but reduce flexibility.
Solution Approach 2:
The patent transforms the secret value from a fixed-parameter construct to a variable-parameter construct. By changing how the secret value is composed (separating it into key-derived and block-size-dependent components), the system achieves both goals: any block size can be used while the secret value size remains optimized at s+b, which is smaller than conventional approaches would require for arbitrary block sizes.
3Reliability
If masking is implemented with block ciphers, then the security against side-channel attacks is improved, but the implementation size increases
Solution Approach 1:
The patent applies dynamics to the masking implementation by making the secret value size adaptable to the block size. This allows the masking scheme to be implemented with an optimized secret value size of s+b, reducing the implementation size compared to fixed-size approaches. The dynamic structure enables efficient masking while maintaining security, as the secret value can be properly divided and protected without requiring excessive overhead.
Solution Approach 2:
The patent changes the parameter structure of the secret value to enable more efficient masking implementation. By organizing the secret value into components sized according to the security parameter s and block size b, the system achieves compact masking implementations. This parameter change reduces the implementation size while maintaining the required security level against side-channel attacks, as the masking can be applied more efficiently to the optimized secret value structure.
Data Source
AI summary
An initial processing unit (21) generates a secret value B from a secret key in authenticated encryption. A function F processing unit (22) repeats a process of setting the secret value B generated by the initial processing unit (21) as an input block of a block cipher, and updating the secret value B using the block cipher. A ciphertext processing unit (23) executes at least one of a process of encrypting a plaintext M and a process of decrypting a ciphertext C, using the secret value B updated by the function F processing unit (23).