Glossary
File Hash
A cryptographic fingerprint of a file — a fixed-length string that changes if any byte of the file changes.
File Hash
A file hash is a cryptographic fingerprint of a file — a fixed-length string (typically 64 hex characters for SHA-256) computed from the file's bytes. If any byte changes, the hash changes; if the file is identical, the hash is identical.
Papyrus computes SHA-256 hashes on every uploaded document. Uses:
- Deduplication: identical files are detected on upload regardless of filename
- Integrity: a stored hash can be re-computed later to verify the file hasn't been corrupted
- Audit evidence: a signed PDF's audit certificate includes the document hash at the moment of signing
- Chain anchoring: the audit log's hash chain uses file hashes as inputs
SHA-256 is collision-resistant: practically impossible to construct two different files that produce the same hash. This is what makes hashes admissible as integrity evidence.