Blockchain Notarization Glossary

SHA-256: A cryptographic hash function that turns any input into a fixed 256-bit (64-hex) fingerprint. It is one-way (you cannot recover the input) and collision-resistant (two different files effectively never share one). notaros uses it to fingerprint your document client-side.
Hash / fingerprint: The fixed-length output of a hash function — a compact, unique stand-in for a file. Anchoring the hash proves the file existed without revealing it.
Proof of existence: Cryptographic evidence that a specific file existed at or before a point in time. See the full explainer.
Anchoring: Recording a hash on a blockchain so the block’s timestamp binds the hash in time. notaros anchors to Base and Bitcoin.
Tamper-evident: A record whose alteration is detectable. Because any change to a file changes its hash, an anchored fingerprint makes tampering obvious.
Timestamp: The time associated with a record. In blockchain notarization, it comes from the block’s own timestamp — set by the network, not the issuer.
Base: An Ethereum layer-2 blockchain offering fast, low-cost transactions. notaros anchors fingerprints in a smart contract on Base for quick, queryable confirmation.
Bitcoin: The most established public blockchain, prized for long-term permanence. notaros commits fingerprints to Bitcoin via OpenTimestamps.
OpenTimestamps: An open standard for Bitcoin-based timestamping that aggregates many hashes into one transaction. notaros’ Bitcoin tier produces a standard .ots proof. See the comparison.
Merkle tree: A structure that combines many hashes into a single root hash, letting one blockchain record commit to many documents efficiently — the mechanism behind OpenTimestamps aggregation.
Timestamping Authority (TSA): A trusted party that signs timestamps under RFC 3161. Blockchain timestamping removes the need to trust such an authority.
RFC 3161: The standard for trusted timestamping via a TSA. Compared with blockchain timestamping here.
notarizedAt(hash): The smart-contract read that returns the on-chain timestamp for a given fingerprint, or zero if it was never anchored. It is how verifiers confirm a proof independently.
Certificate: The self-contained JSON (and full-service PDF) deliverable — {hash, algorithm, chainId, contract, txHash, blockNumber, logIndex, timestamp} plus optional ots — everything needed to verify a proof.
Issuer pin: A security check: the trusted contract is pinned by the verifier from configuration, not read from the certificate, so a self-deployed look-alike contract cannot forge a valid-looking proof.

Blockchain notarization glossary.