Digital Signature Algorithm

The Digital Signature Algorithm (DSA) is a public-key cryptosystem and Federal Information Processing Standard for digital signatures, based on the mathematical concept of modular exponentiation and the discrete logarithm problem. In a public-key cryptosystem, a pair of private and public keys are created: data encrypted with either key can only be decrypted with the other. This means that a signing entity that declared their public key can generate an encrypted signature using their private key, and a verifier can assert the source if it is decrypted correctly using the declared public key. DSA is a variant of the Schnorr and ElGamal signature schemes.^[1]: 486

The National Institute of Standards and Technology (NIST) proposed DSA for use in their Digital Signature Standard (DSS) in 1991, and adopted it as FIPS 186 in 1994.^[2] Five revisions to the initial specification have been released. The newest specification is: FIPS 186-5 from February 2023.^[3] DSA is patented but NIST has made this patent available worldwide royalty-free. Specification FIPS 186-5 indicates DSA will no longer be approved for digital signature generation, but may be used to verify signatures generated prior to the implementation date of that standard.