AES (Advanced Encryption Standard) key extension method

Abstract

The invention discloses an AES (Advanced Encryption Standard) key extension method, and belongs to the technical field of information security. Regarding a condition in which lengths of AES keys are 128 bits and 192 bits, a specific key interception rule is given; and by using the key interception rule, a key with a corresponding length can be intercepted from an output abstract of a sha256 hash function. Regarding an AES encryption algorithm for 128-bit, 192-bit and 256-bit keys, even though an attacker knows a corresponding interception rule, the attacker first needs to obtain an abstract generated by a key via a sha256 hash abstract function; and according to characteristics of the sha256, unless otherwise an output abstract is guessed by traversing, abstract information cannot be obtained by collision; and moreover, the complexity of the output abstract guessed by traversing is as shown in the specification and is obviously higher than the complexity of a 128-bit key and a 192-bitkey. By using the irreversibility of the sha256 hash abstract function, the unidirectionality of the AES key extension method is guaranteed; with the non-collision capability of the sha256, the difficulty of cracking a key violently is improved; and thus, the security of AES key extension is improved.

Description

technical field [0001] The invention belongs to the technical field of information security, and in particular relates to an AES key expansion method. Background technique [0002] In 2001, the US federal government adopted the Rijndael encryption algorithm as the Advanced Encryption Standard (AES) to replace the DES algorithm that could not meet the security requirements. Since its publication, AES has become one of the most popular algorithms in symmetric cryptographic algorithms, and is widely used in communication scenarios such as wireless communication. [0003] AES is an encryption algorithm that supports a plaintext block length of 128 bits. Its key length is divided into three cases, namely 128 bits, 192 bits and 256 bits. The corresponding data processing rounds are 10, 12 and 14 rounds. The round processing part of the AES encryption algorithm is divided into 4 steps: row shifting, column confusion, byte replacement and round key addition. The iterative process ...

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Problems solved by technology

[0005] Since the current AES key expansion algorithm cannot resist the differential key attack, the attacker can deduce the round key above this round and the key of this round through several rounds of differential key analysis while knowing some subkey bytes The following round keys bring hidden dangers to the security of the system

Relevant scholars have used double S-boxes instead of the original single S-boxes on the basis of the original key expansion method, but the increase of S-boxes means the increase of occupied memory, which will increase the hardware requirements of the system

At the same time, relevant literature uses a hash function with an output of 160 bits for key expansion. However, the 160-bit hash function has been broken by scholars such as Wang Xiaoyun, which cannot guarantee the security of key expansion.

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