Masking Method for Asymmetric Cryptography Side-Channel Protection
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Solution Overview
Problem
Asymmetric cryptography implementations in on-board devices are vulnerable to attacks via auxiliary channels, such as side-channel attacks that exploit information leaks through current consumption or electromagnetic radiation, with existing standards like FIPS 186 and RFC 7748-8031-8032 failing to adequately address these issues, especially with the advancement of learning techniques that extract pertinent information from traces.
Innovation Solution
A masking method is introduced that applies a conditional exchange formula using random numbers to mask the exchange operation between vectors manipulating input bits of a secret key, breaking the link between operations and the condition of the input bit, thereby providing protection against information leaks and advanced attacks. This involves drawing random numbers to form intermediate formulas that are equivalent to the original exchange formula, increasing protection without significantly increasing calculation burden.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conditional exchange operations are used in asymmetric cryptography implementations, then cryptographic functionality is achieved, but vulnerability to side-channel attacks increases
Solution Approach 1:
The patent introduces random masks as intermediary elements that are combined with the secret key bits before processing. These masks act as mediators between the secret key and the cryptographic operations, preventing direct correlation between the key bits and the operational traces that side-channel attacks exploit. The masks are systematically eliminated through compensation terms to maintain cryptographic correctness while breaking the information leakage path.
Solution Approach 2:
The patent transforms the original conditional exchange operation parameters by introducing random masking values that change the operational parameters dynamically. The secret key bits are combined with random masks to create masked versions that have different statistical and physical characteristics, making it difficult for attackers to correlate traces with the original key values. This parameter transformation maintains functional equivalence while enhancing security.
2Reliability
If masking operations with random numbers are applied to protect against side-channel attacks, then security against information leaks is improved, but calculation complexity increases
Solution Approach 1:
The patent applies masking operations in advance of the main cryptographic computations by combining secret key bits with random masks before they are used in conditional exchange operations. This preliminary masking prepares the data in a protected form that maintains security throughout subsequent operations. The masks are systematically managed and eliminated through pre-planned compensation terms, avoiding the need for complex post-processing operations.
Solution Approach 2:
The patent segments the cryptographic computation into distinct phases: key masking, conditional exchange operations with masked inputs, and compensation term application. Each phase handles specific aspects of the computation with clearly defined security requirements. This segmentation allows for optimized implementation of each phase while maintaining overall security, reducing the complexity burden compared to a monolithic approach.
3Reliability
If advanced masking techniques are used to counter learning-based attacks, then resistance to sophisticated attacks is improved, but additional calculation time is increased
Solution Approach 1:
The patent integrates masking operations continuously throughout the cryptographic computation rather than as separate pre- and post-processing steps. The masked key bits are used directly in the conditional exchange operations, and compensation terms are applied incrementally to maintain correctness. This continuous approach ensures that security protection is active throughout the entire computation timeline, preventing attackers from isolating and analyzing specific vulnerable operations, while minimizing idle computational time.
Data Source
AI summary
An integrated circuit including a set of security modules configured to implement an asymmetric cryptography operation, the set of modules including a conditional exchange module configured to exchange first and second vectors used to manipulate input bits of a secret key, the conditional exchange module being suitable for applying an exchange formula including a combination of a condition of the input bit with the first and second vectors so that the latter are interchanged only if the condition of the input bit is equal to ‘1’, the conditional exchange module including a masking module suitable for making use of at least one random number to mask said exchange formula before it is applied.