FEISTEL-BASED VARIABLE LENGTH BLOCK CIPHER APPARATUS AND METHOD THEREOF

摘要

Provided are an apparatus and a method for variable length block cipher having a Feistel structure, which may: generate a cipher text having the same bit length as a plain text when encrypting the plain text having a bit length of 8-128; and decode a cipher text to a plain text having the same length as the cipher text. The provided apparatus comprises: an encryption/decryption key generating unit which generates encryption/decryption keys corresponding to the number of rounds set in accordance with the length of a secret key on the basis of the secret key, the length of the secret key, the length of a plain text, and round constant; an encryption/decryption tweak generating unit which generates an encryption/decryption tweak based on the tweak, the length of the tweak, and the length of the plain text; and a cipher text output unit which outputs a cipher text having the same length as the plain text based on the plain text, the length of the plain text, the length of the secret key, the encryption/decryption key, and the encryption/decryption tweak.