Block size (cryptography) facts for kids
In modern cryptography, symmetric key ciphers are generally divided into stream ciphers and block ciphers. Block ciphers operate on a fixed length string of bits. The length of this bit string is the block size. Both the input (plaintext) and output (ciphertext) are the same length; the output cannot be shorter than the input – this is logically required by the Pigeonhole principle and the fact that the cipher must be invertible – and it is simply undesirable for the output to be longer than the input.
The DES is using a block size of 64 bits (8 bytes) while the AES is using a block size of 128 bits (16 bytes). Rijndael, supports block sizes of 128, 192, and 256 bits, although the extra block sizes were not adopted by the AES standard.
Block size (cryptography) Facts for Kids. Kiddle Encyclopedia.