Elementary Information Security, 3rd Edition

▶ 9.2 Block Ciphers

The strongest and most respected modern ciphers are block ciphers. While stream ciphers encrypt bit by bit, block ciphers encrypt fixed-sized blocks of bits. The block cipher takes the block of data and encrypts it into an equal-sized block of data. The old Data Encryption Standard worked with 64-bit blocks of data. The new Advanced Encryption Standard works on 128-bit blocks. To apply a block cipher, we must break the data into block-sized chunks and add padding as needed to match the data to the block size (FIGURE 9.2).

The plaintext that reads “The quick brown fox jumps over the lazy dog” is broken into fixed sized ...