What is the purpose of a hash in information security?

• A. To ensure data confidentiality.
• B. To ensure data integrity.
• C. To replace passwords.
• D. To compress data.

Answer: (B)

Hashes provide a fixed-length fingerprint of data that is used to verify integrity. By computing a hash of the original data and storing or transmitting that digest, you can later recompute the hash and compare it to the stored value. If the data has been altered in any way, even a tiny change typically yields a completely different hash, signaling that the integrity has been compromised. This is why hashes are foundational for ensuring data integrity in transmission, storage, and verification processes. Hashes are not designed to hide content or protect secrecy (that would be encryption), they do not compress data, and they aren’t intended to replace passwords—though hashed (often salted) passwords are stored to protect against disclosure. In practice, you’ll also see hashes used alongside digital signatures or HMACs to provide both integrity and authentication, but the core role of a hash itself is to detect tampering and verify that data remains unchanged.