Encryption Device Segmentation for (b+r)-Bit Security
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Solution Overview
Problem
Existing authenticated ciphers using Tweakable block ciphers face integrity breaches due to collisions of b-bit values, limiting bit security to b bits, and require frequent key updates to maintain security, which is time-consuming and costly.
Innovation Solution
An encryption device that divides plaintext into b-bit and r-bit values, using an encryption function to generate ciphertext and an authenticator, updating a (b+r)-bit value for decryption, thereby achieving (b+r) bits of bit security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Tweakable block cipher with b-bit block size is used for authenticated encryption, then the encryption and decryption functions can be implemented, but the integrity security is limited to b bits due to collisions of b-bit values
Solution Approach 1:
The patent segments the b-bit value updated by the decryption function into two parts: a first b-bit value and a second r-bit value. By updating both values in parallel and using their combination for authentication, the system achieves (b+r)-bit security without increasing the block size of the underlying cipher, thus resolving the contradiction between integrity security and device complexity.
2Reliability
If key updates are performed frequently to maintain security against collisions, then integrity security is improved, but time and computational cost increase
Solution Approach 1:
The patent changes the parameter of security strength from b bits to (b+r) bits by introducing an additional r-bit value. This parameter change allows the system to achieve higher security without frequent key updates, as the effective security level is increased through the extended value space rather than through frequent rekeying.
Data Source
AI summary
A division unit (22) divides a plaintext M every b bits from a beginning, thereby generating b-bit values M1, . . . , Mm-1 and a value Mm having 1 or more bits to b or less bits. An S1 calculation unit (241) assigns a b-bit value H1 to a value M0, and for each integer i of i=1, . . . , m in an ascending order, takes a value Mi-1 as input to an encryption function E, thereby calculating a value S1(i), and calculates a value Ci from the value S1(i) and a value Mi. An S2 calculation unit (242) assigns an r-bit value H2 to a value S2(0), and for each integer i of i=1, . . . , m in an ascending order, calculates a value S2(i) from the value S1(i) and from a value S2(i−1). A ciphertext generation unit (243) generates a ciphertext C from a value Ci for each integer i of i=1, . . . , m. An authenticator generation unit (25) generates a (b+r)-bit authenticator T by using a value S1(m) and a value S2(m).