The Digital Signature Algorithm (DSA) is a cryptographic method used to ensure the authenticity and integrity of digital messages or documents. It generates a unique digital signature for a given message, which can be verified by others using the sender's public key. This process helps confirm that the message has not been altered and that it indeed comes from the claimed sender. DSA is part of the Digital Signature Standard (DSS) established by the National Institute of Standards and Technology (NIST) in the United States. It relies on mathematical principles of modular arithmetic and discrete logarithms, making it secure against various types of attacks.