An alternative to OpenTimestamps
OpenTimestamps is genuinely good software: free, open source, Bitcoin-anchored, and the closest thing this field has to a standard. If you are technical and comfortable at a command line, it may well be all you need. This page is about the cases where it isn't.
What OpenTimestamps does
OpenTimestamps aggregates many hashes into a Merkle tree and commits the tree root to Bitcoin, so a huge number of timestamps share the cost of one transaction. That is why it can be free, and it is an elegant design.
You run a client (CLI, Python library, or the web page), submit a hash, and get back an .ots proof file. Once the aggregated commitment is confirmed, you upgrade the proof and it becomes independently verifiable against the Bitcoin chain.
Created by Peter Todd, it is open source and widely respected. Nothing here is a criticism of the software.
Where the friction is
The trade-offs are real, and they are mostly about operational burden rather than cryptography:
- You must keep the
.otsfile. The proof lives in that file. Lose it and the timestamp is gone — the Bitcoin transaction alone will not help you, because it commits to a Merkle root, not to your hash directly. - Upgrading is a manual step. A fresh proof is "incomplete" until the aggregation is confirmed and you run the upgrade. Plenty of people never do, and discover it years later.
- It assumes technical fluency. The calendar-server model, Merkle aggregation and proof upgrading are not concepts a non-technical claimant will be explaining under pressure.
- The output is not a document. You get a binary proof file, not something you can hand to a lawyer, a client or an insurer.
- Support is community-based. Appropriate for free software; less comfortable when something matters.
Where we are different
| OpenTimestamps | BlockchainSign | |
|---|---|---|
| Cost | Free | One-time fee per certificate |
| Chain | Bitcoin, via aggregation | Ethereum, direct transaction |
| What you keep | An .ots proof file |
A readable certificate with the transaction link |
| Proof completeness | Needs a manual upgrade step | Complete when confirmed |
| If you lose the artefact | Timestamp unrecoverable | The hash is in the transaction itself |
| Interface | CLI / library / web page | Browser, no install |
| Explaining it to a lawyer | You are the documentation | Certificate plus a public Etherscan link |
| Support | Community | Direct |
The substantive difference is the direct transaction. We put your payload hash into the input data of its own Ethereum transaction, so it is readable on Etherscan with "View as UTF-8" by anyone, with no client software and no proof file. That is more expensive per timestamp — which is why we charge and OpenTimestamps doesn't — and much easier to present as evidence.
Be clear about what neither does
Both prove the same narrow thing: a file existed by a time and has not changed. Neither proves authorship, and neither creates a legal right. See proof of existence vs proof of authorship — it applies identically to both tools.
Choose OpenTimestamps if
- You are comfortable with a CLI and will reliably manage proof files.
- You are timestamping at volume and cost matters more than convenience.
- You prefer Bitcoin anchoring, or want to self-host a calendar.
- You are integrating timestamping into software you control.
Choose us if
- You want a certificate you can hand to someone, not a binary proof file.
- You would rather not have a step you can forget.
- You want the hash readable directly in a public transaction.
- You are doing this for a specific document that matters, not at scale.
Both are legitimate. If OpenTimestamps fits how you work, use it — the design is sound and the price is unbeatable.