Which property is essential for hash functions used to verify data integrity in a TA context?

• A. Produce a fixed-length digest; deterministic; preimage resistance; collision resistance
• B. Randomized digest with no determinism
• C. Invertible algorithms
• D. Unbounded digest length

Answer: (A)

When verifying data integrity in a TA context, you want a fingerprint that is reliable, compact, and hard to misuse. A fixed-length digest provides a predictable size for easy storage and comparison, which makes integrity checks efficient and straightforward. Deterministic behavior is essential because the same data must always produce the same digest, allowing repeatable verification over time or across systems. Preimage resistance protects the digest from being used to reveal the original data, so an attacker can’t easily reconstruct what was sent or stored. Collision resistance is also crucial because it prevents two different data inputs from producing the same digest, which would permit forgery or unnoticed data substitution.

The other options undermine these goals: a randomized digest loses reproducibility, so you can’t reliably verify integrity; an invertible algorithm would let someone recover the original data from the digest, weakening security; and an unbounded digest length becomes impractical to store and compare.