The
Data Encryption Standard (
DES, or ) was once a predominant
symmetric-key algorithm for the
encryption of electronic data. It was highly influential in the advancement of modern
cryptography in the academic world. Developed in the early 1970s at
IBM and based on an earlier design by
Horst Feistel, the algorithm was submitted to the
National Bureau of Standards (NBS) following the agency's invitation to propose a candidate for the protection of sensitive, unclassified electronic government data. In 1976, after consultation with the
National Security Agency (NSA), the NBS eventually selected a slightly modified version (strengthened against
differential cryptanalysis, but weakened against
brute force attacks), which was published as an official
Federal Information Processing Standard (FIPS) for the
United States in 1977. The publication of an NSA-approved encryption standard simultaneously resulted in its quick international adoption and widespread academic scrutiny. Controversies arose out of
classified design elements, a relatively short
key length of the
symmetric-key block cipher design, and the involvement of the NSA, nourishing suspicions about a
backdoor. The intense academic scrutiny the algorithm received over time led to the modern understanding of block ciphers and their
cryptanalysis.