RFC 3161 timestamp or blockchain anchoring?
Whoever wants to prove that evidence existed at a point in time needs an independent party. RFC 3161 timestamps and blockchain anchoring solve this differently, with different legal effect.
Leutrim Miftaraj, Founder, Innopulse Consulting GmbH
Published
Key points
- An RFC 3161 timestamp confirms a hash through a timestamp authority, anchoring through a network.
- Only qualified timestamps carry a legal presumption of accuracy.
- For receipt chains, timestamping the current hash regularly is enough.
What this is about
A timestamp following RFC 3161 is a timestamp authority's signed confirmation that a certain hash existed at a certain time. The authority sees only the hash. If it is legally recognized, a qualified timestamp with a legal presumption of accuracy results.
With blockchain anchoring, a hash is written into a transaction on a public blockchain. The time follows from the block in which the transaction was included and can be traced without a central party.
The comparison
| Feature | RFC 3161 timestamp | Blockchain anchoring |
|---|---|---|
| Trust in | A timestamp authority and its anchor | The network and its consensus rules |
| Precision | Seconds, with a stated accuracy | Depends on block time, minutes or longer |
| Cost | Low to moderate per timestamp | Transaction fees, fluctuating |
| Legal effect | With qualified providers, legal presumption (eIDAS, ZertES) | No special legal presumption |
| Verification | Signature and certificate chain up to the anchor | Transaction and block in the network |
| Verification in KYA | Full | Not supported |
When to use what
- RFC 3161 timestamps for evidence that must hold up in audits or court, especially with a qualified provider.
- Blockchain anchoring for scenarios in which no single party is to be considered trustworthy and a legal presumption is not needed.
- Both are possible: the same hash of a receipt chain can be timestamped and anchored.
What counts for agent evidence
Agent evidence is mainly verified when there is a dispute, and then what courts and auditors recognize counts. RFC 3161 timestamps are established there, and qualified timestamps bring a legal presumption in the EU and Switzerland. For receipt chains, timestamping the current hash regularly is enough.
The role of KYA
KYA verifies RFC 3161 timestamps up to the verifying party's trust anchor; an anchored timestamp is required for the highest level, KYA-A4. KYA does not verify blockchain anchoring. You can read a timestamp with the timestamp inspector.
Common misconceptions
- “A blockchain automatically carries more weight as evidence.” Courts assess both as evidence; only qualified timestamps have a legal presumption.
- “A timestamp reveals the content.” The timestamp authority sees only the hash, not the data.
- “Every piece of evidence needs its own timestamp.” With receipt chains, timestamping the current hash regularly is enough; it covers all earlier entries.
Decision guide in three questions
- Must the evidence hold up in court or in an audit? Then an RFC 3161 timestamp, ideally qualified.
- Should no single party enjoy trust? Then anchoring can complement it.
- How precise must the time be? For seconds, RFC 3161 is the better choice.
Cost and operation
RFC 3161 timestamps are billed per request or purchased as a quota; operation is limited to one interface and keeping the responses. Blockchain anchoring incurs transaction fees that fluctuate with network load and requires a funded wallet as well as monitoring of the transactions.
A practical example
A company has the hash of its receipt chain timestamped every hour by a qualified timestamp authority and keeps the responses next to the chain. During an audit, it can show for every entry that it existed by the next full hour at the latest. Additional anchoring would change nothing about this and was therefore not introduced.
Frequently asked questions
Is blockchain anchoring more secure than a timestamp?
It rests on a different trust model, not necessarily on more security. For legal effect, qualified RFC 3161 timestamps clearly have the advantage today.
Does blockchain anchoring have legal effect?
It can be assessed as evidence but has no special legal presumption like qualified timestamps under eIDAS or ZertES.
How precise is an RFC 3161 timestamp?
Usually to the second; the timestamp can also contain a statement of accuracy.
Can KYA verify blockchain anchoring?
No. KYA verifies RFC 3161 timestamps. Blockchain anchoring can be kept in addition but is not counted toward the level.
How often should a receipt chain be timestamped?
As often as the risk requires, for example hourly or daily. Every timestamp proves the state of the chain up to that time.
Can I obtain a timestamp later?
A timestamp only proves that data existed at its own time. A timestamp obtained later does not prove the earlier time.
What happens if a timestamp authority ceases operation?
Timestamps already issued remain verifiable as long as the anchor and certificates are kept. Qualified providers must make provisions for this case.
Sources
- RFC 3161: Time-Stamp Protocol: https://www.rfc-editor.org/rfc/rfc3161
- Verordnung (EU) Nr. 910/2014 (eIDAS): https://eur-lex.europa.eu/eli/reg/2014/910/oj