Safe-Error Defensive Measure for Cryptographic Key Results
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Solution Overview
Problem
Existing cryptographic methods are vulnerable to 'safe error' attacks, particularly when used with algorithms lacking complementation properties like AES, as attackers can determine key bits by observing malfunctions during cryptographic calculations.
Innovation Solution
A method that compares two or more key results and their complementary results for agreement, discarding the complementary result if there's no match, and outputs an error code instead of the result, effectively protecting against single and multiple fault attacks without requiring both keys to be available simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cryptographic calculations are performed with a key in a key register, then the cryptographic function is achieved, but the system becomes vulnerable to safe error attacks where attackers can determine key bits by observing malfunctions
Solution Approach 1:
The patent applies preliminary action by performing cryptographic calculations with both the original key and its complement before final output. The system pre-calculates both key variants and their results, then compares them to detect any anomalies. This advance preparation allows the system to identify potential attacks before they can compromise security, as any deviation between expected and actual results triggers an error response.
Solution Approach 2:
The patent implements feedback by comparing the results of cryptographic calculations performed with complementary keys. The system feeds back the comparison result to determine whether to output the cryptographic result or generate an error. This feedback mechanism allows the system to detect safe error attacks by identifying inconsistencies between calculations performed with complementary key values, thereby maintaining security through continuous verification.
2Reliability
If calculations are performed randomly with the key or its complement, then protection against safe error attacks is provided, but the complexity of the cryptographic system increases
Solution Approach 1:
The patent applies asymmetry by utilizing the complementary relationship between keys (where one key is the bitwise inverse of the other) to create an asymmetric verification process. The system performs calculations with both the original key and its complement, leveraging the mathematical asymmetry between these two key forms to detect attacks. This approach provides robust security without requiring entirely symmetric or identical verification procedures.
Solution Approach 2:
The patent implements parameter changes by systematically varying the key parameter between its original form and its complement form during cryptographic calculations. By changing the key parameter from K to K' (complement), the system performs parallel calculations that can be compared for consistency. This parameter variation approach enables attack detection while maintaining relatively simple implementation, as it only requires modifying the key input parameter rather than the entire cryptographic algorithm.
3Reliability
If multiple key results are compared for agreement, then protection against multiple fault attacks is achieved, but the processing time and computational overhead increase
Solution Approach 1:
The patent applies copying by creating a complementary copy of the cryptographic calculation using the complement key. Instead of performing entirely independent verification calculations, the system generates a copied version of the cryptographic operation with the complementary key and compares the results. This copying approach efficiently detects multiple fault attacks by identifying inconsistencies between the original and complementary calculations, reducing the computational overhead compared to fully independent verification processes.
Data Source
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AI summary
The invention provides a method having a defensive measure designed to protect the calculation against safe-error attacks, said measure comprising the use of a consistency check, which operates without comparison of key results (EK1, EK2, ...) with complementary key results (EK1', EK2'), for example by comparison of key results (EK1, EK2, ...) only among each other and of complementary key results (EK1', EK2') only among each other, or by a consistency check on the key, or by both.