Encryption method, decryption method, device, and program

An encryption/decryption device, comprising:

• a hardware processor;
• a generalized Feistel structure in which data is divided into n pieces and mixing processing with key data is performed;
• and
• at least one diffusion processing unit, under control of the hardware processor, which performs data transformation via linear operation, between rounds of said generalized Feistel structure, wherein
• said diffusion processing unit
• performs linear transformation in which each of n pieces of output data is operated on by two or more pieces of input data, by using an exclusive OR, the linear transformation being placed between rounds of the generalized Feistel structure to compensate for weakness of a diffusion of the generalized Feistel structure;
• and
• wherein said device is adapted for encryption or decryption.

A non-transitory computer readable medium storing an encryption program that causes a computer to perform:

• non-linear transformation processing a plurality of times using a generalized Feistel structure in which data is divided into n pieces and mixing processing with key data is performed;
• and
• diffusion processing, in which data transformation via linear operation is performed, at least once between rounds of said generalized Feistel structure, wherein
• in said diffusion processing,
• linear transformation processing is performed in which each of n pieces of output data is operated on by two or more pieces of input data, by using an exclusive OR, the linear transformation being placed between rounds of the generalized Feistel structure to compensate for weakness of a diffusion of the generalized Feistel structure;
• and
• wherein said program is adapted for encryption or decryption.

An information processing device that has a function to perform an encryption/decryption method for encrypting or decrypting data,

• wherein the information processing device comprises a hardware processor,
• wherein in the encryption/decryption method, by using a generalized Feistel structure in which data is divided into n pieces and mixing processing with key data is performed, diffusion processing, in which data transformation via linear operation is executed, is performed at least once between rounds of said generalized Feistel structure under control of the hardware processor,
• wherein in said diffusion processing, linear transformation is performed in which each of n pieces of output data is operated on by two or more pieces of input data, by using an exclusive OR, the linear transformation being placed between rounds of the generalized Feistel structure to compensate for weakness of a diffusion of the generalized Feistel structure, and
• wherein the method is adapted for encryption or decryption.