What is a hash function used for in the context of digital signatures?

What is a hash function used for in the context of digital signatures?

• A. Encrypts message
• B. Provides confidentiality of content
• C. Creates a digital fingerprint of a message for signing or verification
• D. Serves as a random number generator

Answer: (C)

The main concept tested is that a hash function acts as a digital fingerprint of the message that is signed or verified in a digital signature process. In practice, you compute a fixed-size digest of the message, then sign that digest with your private key. The recipient uses the sender’s public key to verify the signature against the digest they compute from the received message. If any part of the message changes, the digest changes and the signature won’t verify, proving integrity and authenticity. This approach is also efficient because signing a small digest is much faster than signing the entire message. A hash by itself does not provide confidentiality, since the content remains visible and the hash doesn’t hide it, and it’s not a random number generator.

The main concept tested is that a hash function acts as a digital fingerprint of the message that is signed or verified in a digital signature process. In practice, you compute a fixed-size digest of the message, then sign that digest with your private key. The recipient uses the sender’s public key to verify the signature against the digest they compute from the received message. If any part of the message changes, the digest changes and the signature won’t verify, proving integrity and authenticity. This approach is also efficient because signing a small digest is much faster than signing the entire message. A hash by itself does not provide confidentiality, since the content remains visible and the hash doesn’t hide it, and it’s not a random number generator.