Explainers

Anchoring writes a hash of your file into a Bitcoin transaction. Because the ledger is public and append-only, anyone can later check that the hash existed no later than that block, without asking you or any provider. The file itself is never on the chain; only its fingerprint is.

RFC 3161 is the technical protocol: a client sends a hash to a timestamp authority, which returns a signed token binding the hash to a time. eIDAS is the legal layer: when the authority is qualified under eIDAS, Article 41 gives the token a presumption of accuracy across the EU.

A hash is a fixed-length fingerprint of a file. The same file always gives the same hash; any change, however small, gives a different one. A hash proves identity between two copies of a file. Combined with a timestamp, it proves that this exact file existed at that time. Alone, it proves nothing about time.