Which process ensures data integrity verification?

• A. Hashing
• B. Symmetric encryption
• C. Public-key cryptography
• D. Digital signatures

Answer: (A)

Data integrity verification relies on producing a fingerprint of the data that stays the same as long as the data is unchanged. Hashing creates that fingerprint: you run the data through a hash function to produce a fixed-size digest. The critical property is determinism—same input yields the same digest—and the sensitivity to changes—any alteration to the data results in a different digest with overwhelming probability. To verify integrity, you recompute the hash on the received data and compare it to the original digest you trusted or transmitted. If they match, the data is considered intact; if not, something has altered the content.

This works well because hash functions are fast and designed to be collision-resistant and preimage-resistant, meaning it's hard to find two different inputs that produce the same digest or reproduce the original data from the digest. Encryption, by contrast, is about keeping content secret; on its own it doesn’t provide a straightforward check that the data hasn’t been tampered with. Public-key cryptography covers a broader set of techniques, including digital signatures, which do provide integrity along with authenticity and non-repudiation, but the direct, simplest method to verify that data hasn’t changed is hashing. Digital signatures do involve hashing as part of their process, but they add extra layers (authentication and non-repudiation) beyond basic integrity verification.