(What is a digital signature?)

A digital signature is a cryptographic mechanism used to demonstrate the authenticity, data integrity, and non-repudiation of a digital message or document. It is the digital equivalent of a handwritten signature. The process involves creating a message hash and then encrypting the hash with the sender's private key. The recipient can use the sender's public key to decrypt the hash and verify that it matches a hash of the received message. This confirms the sender's identity (authenticity) and that the message has not been altered (integrity).

A. Encryption provides confidentiality (secrecy), whereas a digital signature's primary goals are authenticity, integrity, and non-repudiation.

C. A digital signature is a cryptographic scheme or protocol that uses algorithms (e.g., hashing and asymmetric encryption), not an encryption algorithm itself.

D. A hash function creates a unique identifier (digest) for a file, which is a component of a digital signature, but not the complete signature.

1. National Institute of Standards and Technology (NIST). (2013). FIPS PUB 186-4: Digital Signature Standard (DSS). Section 1, "Introduction," p. 1.

2. Katz, J., & Lindell, Y. (2014). Introduction to Modern Cryptography (2nd ed.). CRC Press. Chapter 12, "Digital Signatures," provides a formal definition and security properties. (A standard textbook in university cryptography courses).

3. Rivest, R. L., Shamir, A., & Adleman, L. (1978). A method for obtaining digital signatures and public-key cryptosystems. Communications of the ACM, 21(2), 120–126. https://doi.org/10.1145/359340.359342 (The foundational academic paper introducing the concept).