What is the primary purpose for using a hash algorithm for a message?

Authentication verifies the identity of a user or system; hashing alone does not prove who created the data - that requires a keyed mechanism such as HMAC or a digital signature.

Confidentiality means keeping data secret from unauthorized parties, which requires encryption; a hash is a one-way function and does not hide the original data.

Availability ensures systems and data are accessible when needed; hashing has no direct role in maintaining uptime or redundancy.

A hash function maps input data of any size to a fixed-length output (digest), and even a single bit change in the input produces a completely different digest. This property allows a recipient to recompute the hash and compare it to a known-good value to detect any tampering or corruption. Integrity - ensuring data has not been modified in transit or at rest - is the core security service that hashing provides.