Cipher Calculation Using Stored Intermediates Against Side-Channel Bias
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Solution Overview
Problem
Existing methods to prevent side-channel attacks using random information are vulnerable to new attack methods that exploit the bias of random information, potentially exposing secret information during cryptographic calculations.
Innovation Solution
A method of calculating a cipher that involves storing a first intermediate result and using it at a different time point from the calculation of a second intermediate result, combined with random values and secret information, to make the value impossible to calculate even if the side-channel attack succeeds, using a physically unclonable function (PUF) for unpredictable digital values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If random information is used for secret calculations to prevent side-channel attacks, then security against traditional side-channel attacks is improved, but vulnerability to new side-channel attacks exploiting random information bias increases
Solution Approach 1:
The patent introduces an intermediary value (first intermediate result) that is stored separately and used at a different time point. This intermediary acts as a mediator between the secret information and the random values, preventing direct exposure of secret information while maintaining the security benefits of randomization. The separation of calculation steps with intermediate storage breaks the direct correlation that new side-channel attacks exploit.
Solution Approach 2:
The patent performs preliminary calculation of the first intermediate result and stores it before the actual cryptographic operation. This preliminary action separates the secret information processing from the random value usage, ensuring that even if random information is later exposed through side-channel attacks, the secret information remains protected because it was already transformed into the intermediate result.
2Reliability
If intermediate results are stored and used at different time points, then security against new side-channel attacks is improved, but calculation complexity increases
Solution Approach 1:
The patent segments the cryptographic calculation into distinct steps with intermediate storage. The calculation is divided into: (1) computing the first intermediate result, (2) storing it, (3) generating random values, (4) computing the second intermediate result, and (5) performing final scalar point multiplication. This segmentation adds structure that improves security while keeping each individual step relatively simple.
Solution Approach 2:
The patent creates a copy of the intermediate result that is stored separately and used later. This copying approach allows the system to maintain the security benefits of separated operations without requiring complex hardware modifications. The stored intermediate result acts as a reusable component that simplifies the overall process while enhancing security.
Data Source
AI summary
Disclosed are a method of calculating a cipher and an electronic device performing the method. The method of calculating the cipher according to an embodiment of the present invention includes reading predetermined secret information t and a first intermediate result based on the secret information t, generating a random value k, calculating a second intermediate result l using the secret information t and the random value k, and performing scalar point multiplication using the first intermediate result and the second intermediate result, wherein the first intermediate result is determined at a different time point from the calculating of the second intermediate result l and stored in a chip and/or memory included in the electronic device.