Method for acquiring lower bound of number of active S boxes in block ciphers
A block cipher and active technology, which is applied to the public key and key distribution of secure communication, can solve the problem of not being able to calculate the lower bound of the number of active S-boxes in the block cipher, and achieve the effect of reducing workload and error probability.
Inactive Publication Date: 2013-12-04
INST OF INFORMATION ENG CAS
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Therefore, the existing methods cannot calculate the lower bound of the number of active S-boxes of these block ciphers
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[0082] In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings and examples.
[0083] see Figure 4 As shown, the method for obtaining the lower bound of the number of active S-boxes of a block cipher in the present invention mainly includes the following processes.
[0084] Step 1. For each input bit and each output bit of each S-box in the block cipher using bit-level permutation as the diffusion layer, introduce a differential variable, and introduce an active variable for each of the S-boxes;
[0085] Step 2. For each of the S-boxes, analyze the limitations of the S-box operation, the round key XOR operation and the bit-level permutation operation on the propagation of the differential mode, and minimize the active variables of all S-boxes in the block cipher. and giving the restriction to the differential variable of eac...
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The invention discloses a method for acquiring a lower bound of the number of active S boxes in block ciphers of bit-level substitution linear diffusion layers. The method includes introducing difference variables into each input bit and each output bit of each S box in the block ciphers with the diffusion layers formed by means of bit-level substitution, and introducing an active variable into each S box; analyzing constraints of S box operation and bit substitution operation on difference-mode propagation, giving constraints on the difference variable of each input bit of each S box, the difference variable of each output bit of each S box and the active variable of each S box in order to minimize the sum of the active variables of all the S boxes in the block ciphers, and creating a mixed integer linear programming problem; solving the mixed integer linear programming problem to acquire the lower bound of the number of the active S boxes. The method has the advantages that cipher design workload and the error probability are greatly reduced, a gap in the field is filled, and the method is similarly applicable to linear diffusion layers constructed by non-maximum distance separable codes.
Description
technical field [0001] The invention relates to the field of information security block cipher design and analysis, in particular to a method for obtaining the lower bound of the number of active S-boxes in the block cipher. Background technique [0002] Symmetric cipher refers to a cryptographic algorithm that uses the same key for encryption and decryption, and is mainly used for data encryption. The block cipher is a widely used symmetric cipher. The encryption of the block cipher refers to changing the plaintext of a fixed length (such as n bits) into a ciphertext of the same length (if the length of the plaintext is n, the length of the ciphertext is also n) under the control of the master key with a length of m bits. Decryption refers to restoring the ciphertext to the plaintext under the control of the same key. Wherein, n is the packet length of the plaintext, m is the length of the primary key, m is a positive integer, and n is a positive integer. [0003] Block ...
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Inventor 胡磊孙思维解永宏宋凌王鹏
Owner INST OF INFORMATION ENG CAS