DES

DES A.K.A. Data Encryption Standard is a symmetric cryptographic algorithm. It uses the same key for encryption and decryption. It is a block cipher that encrypts data 64 bits at a time using a 56-bit key. The key is sometimes completed with an additional byte for parity check. DES is now considered insecure and has been replaced by AES.

Variations such as Triple DES (3DES) and DES-X have been created to improve the security of DES.

Attacks

• Weak keys - Wikipedia CryptoHack

  DES allows for weak keys which are keys that produce the same ciphertext when used for encryption and decryption.

  Some weak keys with valid parity check are:

  • 0x0101010101010101
  • 0xFEFEFEFEFEFEFEFE
  • 0xE0E0E0E0F1F1F1F1
  • 0x1F1F1F1F0E0E0E0E

  Using multiple of these keys in 2 or 3 keys triple DES can also produce a symmetric 3DES block cipher.