Data Encryption Standard is a 56-bit Block Cipher which uses the same key to decrypt or decrypt information. Its underlying method involves complex permutations and shifting binary data into encrypted format as well as mixing and substituting. The procedure is repeated 16 times per round to confuse the relationship between plaintext and the encrypted ciphertext that results.

DES is difficult to crack. Each round is comprised of key mixing, an XOR operation using a 48-bit subkey, expansion permutation as well as S-box permutation. The security of DES is largely dependent on the latter. The 32-bit half-block is divided into eight 6 bit parts and is then processed using an array of eight nonlinear substitutions referred to as S-boxes, which are calculated in a function known as f. Each S-box replaces one of the input bits with four output bits and makes the cipher more difficult to break.

After the S-box procedure the expanded right plain text (RPT) is then combined with the left plain text (LPT) to create the final ciphertext block that is 64 bits. This is the beginning of a series XOR operations that use a 48-bit key that will serve as the basis for an XOR operation with the original key.

The XOR operation that uses the subkey of 48 bits obscures the initial relationship between the plaintext and the ciphertext as much as possible. This is the reason why DES is so secure. The encryption algorithm comes with other features, for instance counters that increase every time a new ciphertext block is created however, they aren’t significant in their ability to secure data.

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