Abstract -This paper develops analytical models for the avalanche characteristics of a class of block ciphers usually referred to as substitution-permutation encryption networks or SPNs. An SPN is considered to display good avalanche characteristics if a one bit change in the plaintext input is expected to result in close to half the ciphertext output bits changing. Good avalanche characteristics are important to ensure that a cipher is not susceptible to statistical attacks and the strength of an SPN's avalanche characteristics may be considered as a measure of the randomness of the ciphertext. The results presented in this paper demonstrate that the avalanche behaviour of encryption networks can be improved by using larger S-boxes. As well, it is shown that increasing the diffusion properties of the S-boxes or replacing the permutations by diffusive linear transformations is effective in improving the network avalanche characteristics.
Good avalanche features are important to ensure that an algorithm is not susceptible to statistical attacks and ensure randomness of the ciphertext REF .
Avalanche Characteristics of Substitution-Permutation Encryption Networks
IEEE Trans. Computers
IEEE Trans. Computers
Computer Science