What is a cryptographic hash function and its uses?

• A. Stores passwords in plaintext for quick access.
• B. Generates encryption keys for symmetric ciphers.
• C. Encrypts data for confidentiality.
• D. Produces fixed-size digest; used for integrity verification, file signing, and password storage with proper salting/hashing.

Answer: (D)

A cryptographic hash function generates a fixed-size digest from input data and is designed to be deterministic, fast, and hard to reverse or collide. This makes it ideal for integrity verification: you hash data and later recompute the hash to confirm nothing changed. For file signing, you hash the content and sign that hash with a private key, so recipients can verify both that the data is intact and who signed it. For password storage, you store a salted hash rather than plaintext, using a slow hashing algorithm so that even if the hash is stolen, guessing passwords is impractical. Since hashing produces a fingerprint without encryption or reversible protection, it isn’t used to hide data or to generate encryption keys.