Choosing a Digital Timestamping Service

How to Choose a Digital Timestamping Service: Seven Questions Worth Asking

A digital timestamping service gives you a verifiable record that a particular file existed in a particular form at or before a particular moment. Services differ in how they create that record, who has to be trusted, what happens to your file, and how much the result is worth if someone challenges it. The right choice depends mostly on what you need the timestamp for.

This guide walks through the questions that actually separate one service from another. It doesn't rank vendors. Certelo is one of the options in this space, and where it fits you'll find it described near the end.

Start with what a timestamp can and can't tell you

Almost every timestamping service works the same way at the core. Your file is run through a hash function such as SHA-256, which produces a short fixed-length fingerprint. That fingerprint, not the file, is what gets timestamped. Change a single byte of the file and the fingerprint changes completely.

So what you end up with is evidence that a file matching this fingerprint existed by this time. That's useful, and it's also all it is. A timestamp on its own doesn't tell anyone who made the file, who owns it, or whether the content is original. If you need those things, a timestamp is one piece of a larger record, alongside drafts, correspondence, version history and, where relevant, formal registration.

Keep that in mind, because it filters out a lot of marketing. A service promising to "prove you own it" is promising something timestamping cannot do.

The seven questions

1. What will you use the timestamp for?

This is the question that decides everything else.

If you want a dated record for your own protection, such as a manuscript, a design, a dataset, a draft contract or a research notebook, almost any reputable method will serve. Your goal is to have something independent of your own computer clock and your own claims.

If you expect the timestamp to be examined in a regulated or legal setting, the requirements get stricter. In the EU, for example, the eIDAS Regulation gives a special status to qualified electronic timestamps. These are issued by providers on the EU trusted list, and they carry a legal presumption of accurate date and time and data integrity. Other electronic timestamps are not automatically rejected as evidence. Article 41 says they can't be denied legal effect merely because they're electronic or not qualified. But they don't get the presumption, so you'd have to establish their reliability another way.

If you have a regulatory requirement for a specific kind of timestamp, find out what that is before you shop. Your lawyer or compliance team should tell you, not a vendor.

2. What kind of timestamp is it?

There are broadly three families, and they rest on different kinds of trust.

Trusted third-party timestamps. The standard here is RFC 3161, the IETF's Time-Stamp Protocol. You send a hash to a Time-Stamping Authority, which signs it together with the current time using its private key. The resulting token is only as trustworthy as the authority and its key. This is well-established and widely supported in document signing workflows. Qualified timestamps under eIDAS are a regulated version of this model.

Blockchain-anchored timestamps. The hash is written into a transaction on a public blockchain, and the block's place in the chain provides the time evidence. Nobody has to trust a single authority's signing key. Anyone can check the record against the chain. The trade-off is that block times are approximate, so the honest claim is "at or before the time this block was recorded", and that the strength of the evidence depends on the chain's security and continued existence.

Hybrid or aggregated approaches. Some services collect many hashes, combine them into a single Merkle root, and anchor only that root. This keeps costs low and is perfectly sound, provided the service gives you the proof path that links your hash to the anchored root.

None of these is simply "better". A qualified RFC 3161 timestamp is often the right answer for EU legal workflows. A public blockchain anchor is attractive when you want verification that doesn't depend on any one company surviving.

3. Does the service ever see your file?

Some services ask you to upload the document so they can hash it. Others hash locally, in your browser or app, and only the fingerprint leaves your device.

For a public poem that's a minor point. For an unreleased product design, a draft patent application, client records or anything under an NDA, it matters a great deal. Check the documentation for where hashing actually happens, and don't rely on the homepage tagline. If you're technical, open your browser's network tab during a test and see what is sent.

Note that local hashing also changes your own responsibility. If the service never holds the file, you have to keep it. If you lose the original, the timestamp can't be matched to anything.

4. Can you verify the result without the vendor?

Imagine the company disappears in five years. Can you still prove the timestamp is genuine?

With a good service the answer is yes, as long as you kept the right pieces. For an RFC 3161 token, you need the token itself and the ability to validate the authority's certificate chain. For a blockchain anchor, you need the transaction reference and any proof path, and then anyone can look up the chain.

Ask whether the proof is exportable in a documented format, whether the verification steps are published, and whether a third party could replicate them with open tools. A proof that can only be checked on the vendor's website is a vendor's assurance, not independent evidence.

5. What exactly gets timestamped?

Hashing a single file is straightforward. But real work is often a folder, a set of versions, a database export or an AI-assisted project with prompts and outputs.

Look at how the service handles several files. Can you timestamp a manifest of hashes? Can you add later versions and keep a clear sequence? A single timestamp on a final PDF says little about how it developed. A chain of dated versions says much more.

One more point is easy to miss. If you hash a document, the fingerprint matches that exact file. Re-saving it in another program, converting it to PDF or letting an editor "normalize" it will produce a different fingerprint. Decide what your canonical version is and keep it unchanged.

6. Does it identify you, and do you want it to?

Timestamping and identity are separate things. Some services tie the record to an account, an email or a verified identity. Others stay anonymous and record only the hash.

Neither is wrong. An identity link can help if you need to show who requested the timestamp, though that still doesn't prove who created the work. Anonymity suits privacy-sensitive uses. Just be sure that the level of identification matches your purpose, and be skeptical of anything suggesting the timestamp establishes authorship by itself.

7. What does it cost over time, and what happens to the proofs?

Look past the first price. Some services charge per timestamp, others by subscription, others by volume through an API. Ask whether proofs remain valid and retrievable if you stop paying. A proof that depends on an active subscription is a weaker archive than one that stays verifiable permanently.

If you timestamp frequently, such as for every build, every report or every batch of research data, check API access and rate limits too.

A short worked example

This is a hypothetical scenario, not a customer case.

A freelance illustrator finishes a commission and wants a dated record before sending it to the client. She doesn't need a court-grade qualified timestamp. She needs something simple and private, because the artwork is confidential until delivery.

Her priorities are local hashing (question 3), independent verification (question 4) and no identity requirement beyond her own account (question 6). A blockchain-anchored service with client-side hashing fits. She keeps the original file, the hash and the proof reference together in her project folder.

Now change the scenario. A company in Germany has to show a supervisory authority when a compliance report was finalized. Here a qualified timestamp from a provider on the EU trusted list is the safer path, because the legal presumption does the work. The same illustrator's blockchain anchor would be a poor fit for that job, and the right advice is to say so plainly.

Red flags

Be careful with services that:

* claim a timestamp proves ownership, originality or authorship

* use words like "court-proof" or "legally bulletproof" with no reference to a jurisdiction or standard

* won't say where hashing happens

* can't tell you how to verify a record without logging into their site

* are vague about which blockchain or authority they use

* make claims about legal acceptance without citing the relevant law or standard

Where Certelo fits

Certelo is a blockchain timestamping and proof-of-existence service. Hashing happens locally in your browser using SHA-256, so the original file doesn't need to be uploaded to create the proof. The hash is anchored on the Electra Protocol blockchain, and the record can later be checked using the original file, the hash or the certificate information.

In terms of the questions above, that means it sits in the blockchain-anchored family, with local hashing and public verification. It provides evidence that a specific fingerprint existed by the recorded blockchain time. It does not establish authorship, ownership or originality, and a blockchain anchor on its own is not a qualified electronic timestamp under eIDAS. If your situation calls for one, you will need a qualified provider, and the two approaches can also be used side by side.

You can see how this works in practice on the Certelo verification page, and the how-it-works page covers the full workflow.

Let's deep dive

What is a digital timestamping service?

It's a service that creates verifiable evidence that a digital file, represented by its hash, existed at or before a given time. The method might be a signing authority, a public blockchain or a combination.

What's the difference between a trusted timestamp and a blockchain timestamp?

A trusted timestamp, usually based on RFC 3161, relies on a time-stamping authority signing your hash. A blockchain timestamp relies on the hash being recorded in a public ledger that anyone can inspect. The first depends on trusting the authority. The second depends on trusting the chain's integrity.

Do I need a qualified timestamp?

Only if a law, regulation or contract asks for one, or if you want the legal presumption eIDAS gives them in the EU. For personal records and many business uses, a non-qualified timestamp is a reasonable choice. Ask a legal professional if the stakes are high.

Does a timestamping service see my file?

It depends on the service. Some require upload, others hash on your device and receive only the hash. Check the documentation. With Certelo, hashing is done locally in the browser.

Can a timestamp prove I created a file?

No. It shows that a file with that fingerprint existed by a certain time. It says nothing about who made it. Authorship is shown through other evidence such as drafts, version history and communications.

What happens if I change the file after timestamping?

The new version has a different hash and won't match the original record. You'd need to timestamp the new version separately. Keep the exact original file if you may need to verify it later.

Is a timestamp the same as a digital signature?

No. A signature ties data to a key holder, which can identify who approved it. A timestamp ties data to a time. They are often used together.

Before you choose

Write down what the timestamp must do, who might examine it, and how sensitive the file is. Those three answers will narrow the field faster than any feature comparison. Then test the verification process yourself before you rely on it. If you can't check a proof without the vendor's help, keep looking.