Modular Exponentiation Randomization via Key Product Auxiliary Number

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Solution Overview

Problem

Existing cryptographic systems face challenges in protecting secret data from side-channel attacks, particularly in modular exponentiation processes, where randomization of exponents is necessary but often requires calculation of Carmichael or Euler's phi functions, which can be cumbersome and resource-intensive.

Innovation Solution

A method for determining a result of modular exponentiation using a randomization auxiliary number calculated as the product of public and private keys minus 1, which is a multiple of the Carmichael function, allowing for efficient randomization without the need for additional function calculations, and can be implemented using the Chinese Remainder Theorem for enhanced security.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If randomization of the exponent is performed using Carmichael function or Euler's phi function, then security against side-channel attacks is improved, but computational complexity and resource consumption increase

Engineering Contradiction:
Improvesecurity against side-channel attacksVSAvoidcomputational complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts only the necessary component for randomization (the auxiliary number derived from key product minus one) without requiring full calculation of Carmichael function or Euler's phi function. This selective extraction maintains security requirements while reducing computational overhead by eliminating unnecessary function calculations.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The auxiliary number for randomization is pre-calculated as the product of public and private keys minus one, which is a multiple of the Carmichael function. This preliminary calculation allows subsequent randomization operations to proceed efficiently without repeatedly computing complex number-theoretic functions during actual cryptographic operations.

Inventive Principle:
Principle #10Preliminary action

2Productivity

If randomization auxiliary number is calculated as product of keys minus one, then computational overhead is reduced, but requirement for pre-known key values increases

Engineering Contradiction:
Improvecomputational efficiencyVSAvoidflexibility in key usage
Core Design Contradiction:
ProductivityVSAdaptability or versatility

Solution Approach 1:

The system uses its own key materials (public key e and private key d) to generate the randomization auxiliary number through the calculation (e×d−1). This self-service approach eliminates dependency on external pre-computed values like Carmichael function or Euler's phi function, allowing the system to autonomously perform efficient randomization using only its existing key pairs.

Inventive Principle:
Principle #25Self-service

Data Source

PatentUS7908641B2Modular exponentiation with randomized exponent
Publication Date: 2011.03.15 INFINEON TECHNOLOGIES AG
  • US7908641B2 patent drawing
  • US7908641B2 patent drawing
  • US7908641B2 patent drawing

AI summary

For the determination of a result of a modular exponentiation, a randomization auxiliary number is employed for the randomization of the exponent on the basis of the product of the public key and the private key less “1”. This randomization auxiliary number may be derived from the private RSA dataset without special functionalities. Thus, low-overhead exponent randomization may be performed for each security protocol universally, to perform a digital signature secure against side-channel attacks.