CyberGlossary

Cryptography

DES (Data Encryption Standard)

Also known as: Data Encryption Standard

Definition

An obsolete 64-bit block cipher with a 56-bit key, standardized by NBS in 1977 and now considered broken because its key space can be exhausted in hours.

DES is a symmetric block cipher based on a 16-round Feistel network that operates on 64-bit blocks with a 56-bit effective key (the 64-bit key has 8 parity bits). It was published as FIPS 46 in 1977 and dominated commercial cryptography for two decades. The 56-bit key is far too short for modern security: the EFF's Deep Crack machine recovered DES keys in under three days in 1998, and modern GPU/FPGA clusters or cloud-based attacks complete an exhaustive search in hours. DES is therefore considered broken and is forbidden by NIST, PCI DSS, and most other standards. It survives only in legacy systems and historical protocols and has been replaced by AES, with Triple DES as a transitional bridge that itself was deprecated in 2023.

Examples

  • DES was used in the original Kerberos v4 protocol.
  • Early ATM PIN-encryption pads used single DES before migrating to 3DES and AES.

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