Final answer:
The U.S. Patent 5,231,668 and FIPS 186 define the Digital Signature Algorithm (DSA), a standard for digital signatures established by NIST and part of public key cryptography algorithms utilized for document and communication authentication.
Step-by-step explanation:
U.S. Patent 5,231,668 and FIPS 186 define the Digital Signature Algorithm (DSA). DSA is a Federal Information Processing Standard for digital signatures. It was proposed by the National Institute of Standards and Technology (NIST) in 1991 for use in their Digital Signature Standard (DSS). The purpose of DSA is to enable users to sign documents and messages in such a way that the signatures can be authenticated and it is computationally infeasible to forge or repudiate a signature. The algorithm uses mathematical techniques from modular arithmetic and discrete logarithms, which are key concepts in the field of number theory.
DSA is part of the broader family of public key cryptographic algorithms, which includes RSA and Elliptic Curve (EC) cryptography. Unlike RSA, which can also be used for encryption, DSA is used exclusively for digital signatures. The use of algorithms like DSA is crucial in the field of digital security, especially in applications that require the authentication of digital documents and communications.