Checksum

A checksum (more generally a cryptographic hash such as SHA-256) is a short digest computed from a file's bytes. Recalculating and comparing digests later reveals whether the file has changed—whether by accidental Bit rot, transfer error, or tampering.

In archives

Repositories record checksums at ingest and re-verify on a schedule. Mismatches trigger repair from another copy (LOCKSS-style networks rely on this comparison across peers).

See also

• Digital preservation
• LOCKSS
• WARC

Sources

• NIST and library fixity guidance (general).
• OAIS-related practice notes.