How to timestamp a contract
Contract disputes are often not about what the agreement said in principle but about which version was in force, and whether a document produced later is the one that was actually signed. A timestamp settles both questions cheaply, without replacing your e-signature workflow.
The problem timestamping solves
E-signature platforms prove that named parties assented to a document. That is necessary and usually sufficient — until one of these comes up:
- Version disputes. Several drafts circulated. Which one was on the table on the 14th?
- Post-signature alteration. A party produces a copy differing in one clause.
- Pre-contractual documents. Term sheets, NDAs, specifications and side letters that were never formally signed but shape the deal.
- Provider risk. Your evidence lives in a vendor's account. Vendors get acquired, accounts lapse, exports go stale.
A blockchain timestamp addresses all four, because the proof is independent of any vendor and independent of the signature itself.
How it works for a contract
- Hash the final PDF or DOCX. Done in your browser; the contract never leaves your device — which matters when the document is confidential.
- Record the hash on Ethereum. A permanent public transaction. The hash reveals nothing about the contents.
- Store the certificate with the contract. It contains the hash, the transaction and a public verification link.
Later, re-hashing the document either matches the record or does not. There is no interpretation to argue over.
Confidentiality
Worth being explicit, because it is the first question counsel asks: nothing about the contract is published. A SHA-256 hash is a one-way fingerprint. It cannot be reversed, and it reveals neither the parties, the terms, nor the length of the document. What goes on-chain is 64 characters of hexadecimal.
This is what makes the technique usable for material that cannot be disclosed — which, in practice, is most commercial agreements.
Where it fits with e-signature
Use both. They prove different things:
| E-signature | Blockchain timestamp | |
|---|---|---|
| Proves who assented | Yes | No |
| Proves the version and its date | Within the platform | Independently, publicly |
| Survives the vendor disappearing | Not reliably | Yes |
| Covers unsigned documents | No | Yes |
| Reveals the contents | To the platform | Never |
See blockchain document signing for how the two combine, or the DocuSign comparison for the specific case.
What to timestamp, and when
- The executed contract, on the day of execution.
- Each material draft as it is exchanged, so the negotiation sequence is dated.
- NDAs and term sheets — the documents least likely to be formally signed and most likely to be disputed.
- Attachments and schedules, which are the parts that quietly get swapped.
Keep every timestamped file byte-identical; any edit changes the hash. Timestamp revisions as new records rather than replacing the old ones.
The record establishes existence and integrity at a time, not authorship or assent — see proof of existence vs proof of authorship. For contracts, that is precisely the contested fact.