Feistel Network Structure - 16 Rounds of Encryption
DES was adopted as a federal standard in 1977 and uses a 56-bit key to encrypt 64-bit blocks. The Feistel structure splits data into left and right halves, applying 16 rounds of substitution and permutation. Each round uses a different subkey derived from the main key. While DES is now considered insecure due to its short key length, its Feistel design influenced many modern ciphers including 3DES and Blowfish.