Mastering Blockchain - Second Edition

Block ciphers

Block ciphers are encryption algorithms that break up the text to be encrypted (plaintext) into blocks of a fixed length and apply the encryption block-by-block. Block ciphers are generally built using a design strategy known as a Feistel cipher. Recent block ciphers, such as AES (Rijndael) have been built using a combination of substitution and permutation called a Substitution-Permutation Network (SPN).

Feistel ciphers are based on the Feistel network, which is a structure developed by Horst Feistel. This structure is based on the idea of combining multiple rounds of repeated operations to achieve desirable cryptographic properties known as confusion and diffusion. Feistel networks operate by dividing data into two blocks ...