Cipher Structure Resistance Evaluation Method
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Solution Overview
Problem
There is a need for evaluating and optimizing cipher structures in terms of resistance to differential and linear cryptanalysis, particularly for those using differently-sized substitution boxes, as existing methods lack efficiency and effectiveness in assessing their cryptographic strength.
Innovation Solution
A method and apparatus for evaluating resistance to differential and linear cryptanalysis by determining the generalized minimum number of non-zero symbols in a diffusion element, dividing the input into subset inputs, calculating the maximum differential or linear characteristic probability using specific equations, and selecting transformations or confusion elements to enhance resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If differently-sized S-boxes are used in a cipher structure, then cryptographic strength may be improved, but the ability to evaluate resistance to differential and linear cryptanalysis becomes insufficient
Solution Approach 1:
The patent segments the evaluation process by dividing the cipher structure into diffusion elements and confusion elements, and further dividing the input into subset inputs corresponding to each confusion element. This segmentation allows the complex evaluation of differently-sized S-boxes to be broken down into manageable calculations of generalized minimum numbers and subset numbers, making the evaluation feasible while maintaining comprehensive cryptographic analysis.
Solution Approach 2:
The patent introduces new evaluation parameters including the generalized minimum number NG of non-zero symbols, subset numbers NSi for each subset input, and the derived quantity NW = NG - SN. These parameters transform the complex cryptographic evaluation into systematic calculations that can assess resistance to differential and linear cryptanalysis for differently-sized S-boxes in a structured manner.
2Ease of manufacture
If identically-sized S-boxes are used, then design simplicity is maintained, but cryptographic optimization for differently-sized S-boxes cannot be achieved
Solution Approach 1:
The patent enables the evaluation and optimization of differently-sized S-boxes by introducing the generalized minimum number NG and subset numbers NSi as calculable parameters. These parameters allow cryptographers to systematically assess and compare different S-box configurations, making it possible to optimize cryptographic strength while maintaining design feasibility through structured evaluation procedures.
Data Source
AI summary
Disclosed is a method for evaluating resistance to cryptanalysis of a cipher structure having a diffusion element including a linear transformation placed between differently-sized confusion elements at an input and an output of the diffusion element. A generalized minimum number of non-zero symbols at the diffusion element's input and output is determined. The diffusion element's input is divided into subset inputs, each having a size corresponding to the size of each confusion element at the diffusion element input. For each subset input, a subset number of non-zero symbols at the subset input and the diffusion element output is determined. Each subset number is summed to generate a summed subset number. The summed subset number is subtracted from the generalized minimum number to generate a worst-case number. An upper bound of a maximum differential characteristic probability is calculated and used to evaluate the cipher structure.