Bit-Mixer Round Key Generation for Cryptographic Security
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Solution Overview
Problem
Current cryptographic systems face inefficiencies in generating round keys for block ciphers, leading to slow operation speeds and high power consumption, while also leaking exploitable information through side channels due to the complexity of key generation and the use of correlated round keys.
Innovation Solution
The method involves using bit-mixer operations, such as XOR trees, substitution-permutation networks, and double-mix Feistel networks, to generate highly uncorrelated round keys from secret and public key materials, reducing side channel leakage and improving security and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If simple key-schedule algorithms like LFSR are used, then the key generation is fast and easy to compute, but the resulting round-keys are highly correlated and leak exploitable information through side channels
Solution Approach 1:
The patent introduces bit-mixer operations as intermediary components between the simple LFSR key schedule and the final round keys. These bit-mixers (including XOR trees, substitution-permutation networks, and Feistel networks) act as mediators that take the correlated output from LFSR and transform it into uncorrelated round keys, thereby maintaining fast key generation while eliminating correlation leakage.
Solution Approach 2:
The patent transforms the key generation process by changing the operational parameters from simple linear operations to complex non-linear bit-mixer operations. This parameter change includes introducing substitution boxes, permutation operations, and Feistel network structures that fundamentally alter how round keys are derived, converting correlated sequences into uncorrelated keys while maintaining computational efficiency.
2Reliability
If complex key-schedule algorithms are used to produce uncorrelated round-keys, then security is improved, but the cipher consumes much time and power at each round
Solution Approach 1:
The patent segments the key generation process into two distinct phases: a fast pre-computation phase using simple LFSR operations, and a transformation phase using efficient bit-mixer operations. This segmentation allows the system to leverage the speed of simple operations for generating key material while using optimized mixer operations to achieve uncorrelation, thereby reducing overall power consumption compared to using complex operations throughout.
Solution Approach 2:
The patent extracts the complex non-linear transformation requirements from the main key generation loop and isolates them into dedicated bit-mixer components. By separating the linear LFSR generation from the non-linear mixing operations, the system can optimize each part independently, using power-efficient implementations of the mixing operations that consume significantly less energy than traditional complex key-schedule algorithms.
3Reliability
If many key-schedule steps are performed to achieve uncorrelated round-keys, then security is improved, but the time consumed at each round increases considerably
Solution Approach 1:
The patent performs preliminary uncorrelation operations during the key generation phase using efficient bit-mixer structures. By pre-computing the non-linear transformations and storing the results, the system eliminates the need for repeated complex operations during actual encryption/decryption rounds. This preliminary action ensures that round keys are generated quickly with minimal time loss during operational phases.
Solution Approach 2:
The patent replaces traditional mechanical key-schedule operations (multiple sequential transformation steps) with optimized bit-mixer structures that achieve the same uncorrelation effect in fewer operations. The substitution includes using parallel XOR tree structures, compact substitution-permutation networks, and streamlined Feistel operations that reduce the number of computational steps required compared to conventional approaches.
4Reliability
If sequential round-key generation is used in hardware, then all round-keys must be generated before decryption can begin, but this causes an initial delay
Solution Approach 1:
The patent introduces dynamic key generation capabilities where the bit-mixer operations can be configured to generate round keys on-demand rather than requiring complete pre-generation. The system dynamically adapts the key schedule execution based on operational needs, allowing decryption to start as soon as the first round key is available while maintaining the ability to generate subsequent keys as needed, thereby eliminating the initial delay without compromising completeness.
Data Source
AI summary
System and methods for generating round keys for a cryptographic operation are disclosed. The systems and method can use logic circuits that are operable to: obtain first inputs and second inputs; perform a bit-mixer operation on each of the first inputs and the second inputs; and generate round keys based on the performing the bit-mixer operation. The first inputs include a plurality of equal sized subkeys from a key material that is divided into a plurality of equal sized key material sub-blocks, a cipher key and the second inputs include a random input, one or more previous round keys, a round number. The cryptographic operation includes a cipher, a hash function, or a stream generator. The bit-mixer operation includes an exclusive-OR (XOR) tree, a substitution-permutation network, or a double-mix Feistel network, or a Rotate-Add-XOR (RAX) construction.