OpenTimestamps (OTS) is an open-source[2] project that aims to provide a standard format for blockchain timestamping.

[3] With the advent of systems like Bitcoin, it is possible to create and verify proofs of existence of documents (timestamps) without relying on a trusted third party; this represents an enhancement in terms of security, since it excludes the possibility of a malicious (or careless) trusted third party to compromise the timestamp.

OTS provides users multiple and easy ways to create and independently verify timestamps:[citation needed] In the following sections it is shown an example of the usage of the Python client.

Each of the calendar servers will add the received hash to its Merkle tree and return the necessary response to generate the initial OTS file.

This will communicate with the calendar servers and update the OTS file with the Bitcoin block header attestation.

The user must also have an up-to-date Bitcoin node[f] on their own machine to perform the verification without relying on trusted third parties.