Cryptographic Circuit Scrambled Substitution Table Side-Channel Protection
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Solution Overview
Problem
Existing cryptographic systems are vulnerable to side-channel attacks, particularly those targeting power consumption and timing signals during substitution operations, as hackers can exploit the visibility of these operations to recover the secret key.
Innovation Solution
Implementing a method that uses scrambled substitution tables with a series of substitution operations, including a real set based on a real scrambling key and multiple dummy sets based on false scrambling keys, where the position of the real set is randomly selected, and the same group of false scrambling keys is applied across multiple dummy sets, generated by shifting the real scrambling key.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dummy substitution operations are added to protect against side-channel attacks, then security against side-channel attacks is improved, but computational overhead increases
Solution Approach 1:
The substitution operation is segmented into multiple series, where each series contains one real substitution operation and multiple dummy substitution operations. This segmentation allows the system to distribute the protective dummy operations across different segments (series) while maintaining the core functional substitution operation, thereby achieving security protection with controlled computational overhead.
Solution Approach 2:
The patent applies partial action by performing only the necessary number of dummy operations (m-1 dummies per real operation) rather than excessive redundant operations. The parameter m is optimized to provide sufficient protection against side-channel attacks while minimizing the time overhead, representing a balanced partial action approach rather than complete or excessive dummy operations.
2Difficulty of detecting and measuring
If multiple dummy substitution operations with different scrambling keys are performed, then the correlation between side-channel signals and secret key is complicated, but the complexity of key management increases
Solution Approach 1:
The false scrambling keys are pre-generated from the real scrambling key using a deterministic function (cyclic shifts) before the substitution operations are executed. This preliminary action eliminates the need for separate key management systems for dummy operations, as all keys are derived from a single real key, thereby complicating side-channel analysis while maintaining simple key management.
Solution Approach 2:
A key derivation function (cyclic shift operation) acts as an intermediary between the real scrambling key and the multiple false scrambling keys. This intermediary mechanism allows the system to generate multiple distinct keys from a single source key, achieving the goal of complicating side-channel correlations without requiring multiple independent key management systems.
3Reliability
If the position of the real substitution operation is randomly selected, then protection against timing attacks is improved, but the complexity of operation selection increases
Solution Approach 1:
The selection of the real substitution operation position follows a periodic pattern based on a random value r, where the position is determined by a systematic selection process within the series. This periodic yet randomized selection provides protection against timing attacks while maintaining relatively simple operation selection logic compared to completely random selection mechanisms.
Data Source
AI summary
A cryptographic circuit performs a substitution operation of a cryptographic algorithm based on a scrambled substitution table. For each set of one or more substitution operations of the cryptographic algorithm, the circuit performs a series of sets of one or more substitution operations of which: one is a real set of one or more substitution operations defined by the cryptographic algorithm, the real set of one or more substitution operations being based on input data modified by a real scrambling key; and one or more others are dummy sets of one or more substitution operations, each dummy set of one or more dummy substitution operations being based on input data modified by a different false scrambling key.