A five-round algebraic property of the advanced encryption standard

This paper presents a five-round algebraic property of the Advanced Encryption Standard (AES). In the proposed property, we modify twenty bytes from five intermediate values at some fixed locations in five consecutive rounds, and we show that after five rounds of operations, such modifications do not change the intermediate result and finally still produce the same ciphertext. We introduce an algorithm named δ, and the algorithm accepts a plaintext and a key as two inputs and outputs twenty bytes, which are used in the five-round property. We demonstrate that the δ algorithm has 20 variants for AES-128, 28 variants for AES-192 and 36 variants for AES-256. By employing the δ algorithm, we define a modified version of the AES algorithm, the δAES. The δAES calls the δ algorithm to generate twenty bytes, and uses these twenty bytes to modify the AES round keys. The δAES employs the same key scheduling algorithm, constants and round function as the AES. For a plaintext and a key, the AES and the δAES produce the same ciphertext

Journal of Indian Academy of Dental Specialist Researchers : JIADSR

We present a five-round algebraic property of the advanced encryption standard (AES), and we show that this algebraic property can be used to analyse the internal structure of ALPHA-MAC whose underlying block cipher is AES. In the proposed property, we modify 20 bytes from five intermediate values at some fixed locations in five consecutive rounds, and we show that after five rounds of operations, such modifications do not change the intermediate result and finally, still produce the same ciphertext. By employing the proposed five-round algebraic property of AES, we provide a method to find second preimages of the ALPHA-MAC based on the assumption that a key or an intermediate value is known. We also show that our idea can also be used to find internal collisions of the ALPHA-MAC under the same assumption