---
title: "Timestamp (RFC 3161): definition | KYA glossary"
url: https://knowyouragent.ch/en/knowledge/glossary/rfc-3161-timestamp
lang: en
updated: 2026-10-12
license: © Innopulse Consulting GmbH
---

# Timestamp (RFC 3161)

An RFC 3161 timestamp is a timestamp authority's signed confirmation that a specific hash existed at a specific time.

The timestamp fixes a receipt in time: anyone who changes it afterwards breaks the binding. How much it proves depends on the timestamp authority. Qualified timestamps under ZertES or eIDAS have special legal effect but require a recognized provider.

## Example

A company has a timestamp authority sign the hash of every [receipt chain](https://knowyouragent.ch/en/knowledge/glossary/receipt-chain) each hour. The timestamp proves that the chain existed at that time at the latest, without the authority seeing the content.

## How it differs

The time in one's own log is a claim; a timestamp following RFC 3161 is evidence from an independent authority. It is qualified when the authority is legally recognized.

## In practice

- Have only the hash timestamped, never the content. This protects confidential data and is fully sufficient to prove the point in time.
- Choose a timestamp authority whose root certificate your verifying parties know and accept, ideally a recognized trust service for disputes.
- Keep timestamps together with the timestamped data. Without the original data, the timestamp's binding to the content can no longer be verified.

## Role in KYA

KYA verifies the timestamp's CMS signature, its purpose, the binding to the content and the path to the [trust anchor](https://knowyouragent.ch/en/knowledge/glossary/trust-anchor) provided. An anchored timestamp is required for level KYA-A4.

Related check: [Timestamp](https://knowyouragent.ch/en/method/checks) (`timestamp_assurance`). Is the RFC 3161 timestamp valid, bound to the content and traceable to an anchor of the [verifying party](https://knowyouragent.ch/en/knowledge/glossary/verifying-party)?

[Verify now: open a matching example](https://knowyouragent.ch/en/verify?beispiel=paket)

## Frequently asked questions

### What is a timestamp following RFC 3161?

A signed confirmation by a timestamp authority that a certain hash existed at a certain time.

### Does the timestamp authority see my data?

No. The authority receives only the hash, not the content.

### How do I verify a timestamp?

Paste the timestamp on the verification page or load it as a file, and provide the authority's anchor under “Trust of the verifying party”.

### How long does a timestamp remain verifiable?

As long as the authority's anchor is known and the method is secure. For very long periods, timestamps are renewed before they expire.

### Do I need a separate timestamp for every receipt?

No. Timestamping the current hash of a receipt chain is enough; it also secures all earlier entries in the chain.

### What does a timestamp cost?

That depends on the provider. There are freely accessible timestamp services for testing and paid services, including qualified providers with legal recognition. KYA verifies both kinds, provided the anchor is set.

## Sources

- [RFC 3161: Time-Stamp Protocol](https://www.rfc-editor.org/rfc/rfc3161)

## Related terms

- [Trust anchor](https://knowyouragent.ch/en/knowledge/glossary/trust-anchor)
- [Receipt chain](https://knowyouragent.ch/en/knowledge/glossary/receipt-chain)

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Quelle: https://knowyouragent.ch/en/knowledge/glossary/rfc-3161-timestamp · KYA – Know Your Agent