Expansion system and method for 256-bit keys

Abstract

The invention discloses an expansion system and a method for 256-bit keys based on an advanced encryption standard (AES), and mainly solves the problems of low efficiency and high power consumption in a key expansion process in the existing 256-bit AES. The process includes storing an initial key in the first round of key expansion, taking the first four rows as a round key of the key expansion in the first round, and performing word cycle, byte replacement, and bitwise XOR operations; executing a new byte replacement and a secondary bitwise XOR operation according to serial number n; taking results of the two bitwise XOR operations as a round key and storing in a local register and an external storage cell for the usage of encryption process reading; and repeating the operations for round keys obtained in a former round in following rounds until 14 round keys are obtained, and finishing key expansion. According to the expansion system and the method for the 256-bit keys, instantaneity of key expansion and reusability of round keys are achieved simultaneously, key expansion with high efficiency and low power consumption is achieved, and the expansion system and the method are suitable for key expansion processes of the 256-bit AES.

Description

technical field [0001] The invention belongs to the technical field of safety, relates to data encryption, in particular to a key expansion method in the Advanced Encryption Standard AES, which can be used for network communication. Background technique [0002] The Advanced Encryption Standard AES is an encryption algorithm published by NIST in November 2001 to replace the data encryption standard DES. At present, the AES algorithm has been widely used in high-end products such as encryption protocols, communication terminals and servers. [0003] The AES algorithm adopts a subset of the Rijnddel symmetric key algorithm, and supports groups with a length of 128 bits and keys with lengths of 128, 192, and 256 bits. The algorithm obtains the round key by performing key expansion on the initial key, and uses the round key to encrypt and decrypt 128-bit data blocks. [0004] In the AES algorithm, depending on the length of the initial key, the number of rounds r of encryption...

AI Technical Summary

Problems solved by technology

[0005] There are currently two widely used key expansion methods: one is the real-time key expansion method used in "A Rijndael Cryptoprocessor Using Shared On-the-fly Key Scheduler", that is, the key expansion unit performs key expansion at the same time Provide a round key for the encryption process; the disadvantage of this method is that the round key cannot be reused, so for occasions where the amount of data is large and the round key needs to be used continuously, the power consumption caused by the continuous execution of the key expansion operation is relatively large; The other is the pre-key expansion method used in "An Optimized FPGA Implementation Method of AES Algorithm", that is, the key expansion is performed first to generate all the round keys and stored in the memory, and then encrypted; in this method In the process of encryption, since the encryption process can only be performed after the key expansion is completed, the time required for encryption is increased and the efficiency of the entire encryption process is reduced.

Images