Which statement about a hash and document integrity is correct?

• A. A hash provides user authentication.
• B. A hash encrypts the document for confidentiality.
• C. A hash helps verify that the content has not been altered since signing.
• D. A hash compresses the document.

Answer: (C)

Hashes create a unique fingerprint of data, so any change to the content yields a different digest. When you sign that hash with a private key, someone else can recompute the hash and verify the signature with the public key to confirm both that the content is unchanged and who signed it. In that sense, a hash helps verify that the content has not been altered since signing. The other statements don’t fit: a hash doesn’t provide user authentication, it doesn’t encrypt data to keep it confidential, and while a hash output has a fixed size, hashing isn’t intended as a method of data compression.