Hash comparison checks whether two files are identical by calculating a cryptographic hash for each and comparing the results. A hash is a fixed-length fingerprint of a file’s contents; even a small change usually produces a different value. Matching hashes provide strong evidence that the files are byte-for-byte the same, provided a secure hash algorithm is used.
In cyber security, hash comparison helps verify evidence integrity, detect unauthorized changes, and confirm that a downloaded or copied file matches a trusted original. During an investigation into an alleged data leak, investigators can compare hashes of collected files with known copies to check whether they changed during handling. Hashes do not prove who created a file, where it came from, or whether its contents are genuine; provenance and other evidence must be assessed separately.