10 Facts About Block cipher

In cryptography, a block cipher is a deterministic algorithm operating on fixed-length groups of bits, called blocks.

Root of all cryptographic block formats used within the Payment Card Industry Data Security Standard and American National Standards Institute standards lies with the Atalla Key Block cipher, which was a key innovation of the Atalla Box, the first hardware security module.

Further, a good block cipher is designed to avoid side-channel attacks, such as branch prediction and input-dependent memory accesses that might leak secret data via the cache state or the execution time.

Finally, the Block cipher should be easily cryptanalyzable, such that it can be shown how many rounds the Block cipher needs to be reduced to, so that the existing cryptographic attacks would work – and, conversely, that it can be shown that the number of actual rounds is large enough to protect against them.

One important type of iterated block cipher known as a substitution–permutation network takes a block of the plaintext and the key as inputs, and applies several alternating rounds consisting of a substitution stage followed by a permutation stage—to produce each block of ciphertext output.

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Informally, a block cipher is secure in the standard model if an attacker cannot tell the difference between the block cipher and a random permutation.

The block cipher E is a pseudo-random permutation if no adversary has an advantage significantly greater than 0, given specified restrictions on q and the adversary's running time.

International Data Encryption Algorithm is a block cipher designed by James Massey of ETH Zurich and Xuejia Lai; it was first described in 1991, as an intended replacement for DES.

RC5 is a block cipher designed by Ronald Rivest in 1994 which, unlike many other ciphers, has a variable block size, key size and number of rounds.

Rijndael Block cipher developed by Belgian cryptographers, Joan Daemen and Vincent Rijmen was one of the competing designs to replace DES.