Blockchain timestamp on SKALE: what Chaindoc puts on chain and what it proves

A blockchain timestamp is a file's fingerprint written into a public ledger, so anyone can later show that the file existed, unchanged, by the time its block was sealed. Chaindoc writes them on SKALE at two moments: when you publish a document version, and when the last signer finishes. Neither record holds the document, a name or an email address. They hold hashes and signature proofs, and the transaction link lets the other side check them without asking us. What a blockchain timestamp doesn't do is make a signature valid. That comes from signing the document properly under eIDAS or the ESIGN Act.

Every e-signature tool keeps an audit trail. The trouble is where it lives: on the vendor's servers, in a database the vendor can edit, export and, on a bad day, lose. If your counterparty says the PDF you produce isn't the one they signed, the audit trail is your word plus your vendor's word.

A hash on a public chain changes who you have to trust. A hash is a fixed-length string computed from a file's bytes; change one comma and the string comes out completely different. Once it sits in a finalised block, nobody can quietly edit it. Not your counterparty, not Chaindoc, not a database admin at 2 a.m. Anyone who holds the file can recompute the hash and compare.

That's all blockchain timestamping is, and it's an old idea. OpenTimestamps has done it on Bitcoin for years, with free calendar servers that batch many hashes into one transaction so nobody pays a fee per file. Chaindoc does the same job inside the signing flow, so the proof exists without anyone having to remember to make it.

Honest caveat: the chain proves the file and a date. It says nothing about who's behind an email address. Non-repudiation, a signer's inability to plausibly deny signing, rests on the signature and the audit trail together. The chain alone can't carry it, and any vendor who tells you otherwise is overselling.

Any public chain can hold a hash. The choice comes down to three questions: who pays for each transaction, how long you wait for a final answer, and who secures the record afterwards. Chaindoc writes to Calypso, one of the public SKALE chains on Ethereum.

Gas the signer never pays

On most chains every transaction costs gas, paid in a token with a market price. For a signing tool that means a fee per document that moves with crypto markets, plus a wallet somewhere. SKALE's Ethereum chains run with zero gas fees: transactions still consume gas, but it's paid in sFUEL, a token that SKALE's documentation says has no monetary value. The chain's owner carries the cost, not the person sending the transaction. From the user's side it works like gasless transactions: the gas exists, but nobody pays money for it.

In practice Chaindoc's server sends the transactions. Signers never see a wallet, never buy a token and never pay per signature, and there's no gas line on anyone's invoice. What you pay for is the Chaindoc plan.

Finality you don't wait for

SKALE describes each of its chains as an EVM Layer 1 with instant finality: a block is final once two-thirds of the chain's validator committee signs it with a BLS threshold signature, so there are no reorganisations and no counting confirmations. For a signing flow that matters more than raw speed. The moment the record exists, it's final, and the verification report can point at it straight away. Bitcoin, by comparison, adds a block roughly every ten minutes, and careful verifiers wait for several.

What it costs in trust

Here's the trade-off, and it's a real one. SKALE says plainly that it isn't a rollup or a sidechain. Each chain keeps its own state and consensus, secured by a validator pool that stakes on Ethereum, while Ethereum hosts the contracts that run the network. So a record on Calypso is as durable as SKALE's validator set, not as Bitcoin's proof of work. For a document proof we think that's the right call: cheap enough to write for every document, fast enough to be in the report, public enough for the other side to check. If one file matters enough to want a second anchor, nothing stops you from stamping it with OpenTimestamps as well.

People tend to assume a blockchain timestamp stores far more than it does. Here's the complete list for Chaindoc, the same answer the home page gives. The split is deliberate. A public chain is permanent and readable by anyone, which is exactly why personal data stays off it, including the result of an optional identity check.

You don't need Chaindoc to be online for this, and you don't need to trust our verifier. You need the signed file, the verification report and a terminal.

1. 1.
   Hash your copy. On macOS or Linux, run shasum -a 256 contract.pdf. In Windows PowerShell, Get-FileHash contract.pdf uses SHA-256 by default. You get a 64-character string.
2. 2.
   Compare that string with the hash printed in the verification report. A single different character means a different file.
3. 3.
   Open the transaction link from the report. It's a page on SKALE's public block explorer, showing the transaction that carries the record, its block, and the block's date and time.
4. 4.
   Read the blockchain timestamp as "no later than". The block time tells you the file existed in exactly this form by that moment. It doesn't tell you when someone first wrote it.

Prefer not to open a terminal? Chaindoc's PDF verification service runs the same comparison once you confirm your email with a one-time code. For a file signed elsewhere with a qualified certificate, signature verification checks the certificate chain instead, which answers a different question.

Why bother doing it by hand at all? Because the point of a public record is that the other side can run the check too, with tools nobody controls.

Short answer: it isn't the thing that binds anyone. The signature does that. A blockchain timestamp is evidence about the file, namely that it existed by a certain time and hasn't changed since.

In the EU

Article 25 of the eIDAS Regulation says an electronic signature can't be denied legal effect just because it's electronic. Chaindoc issues advanced electronic signatures (AES, as PAdES-BES) and isn't a qualified trust service provider (QTSP), so where a law demands a qualified signature, you need a QTSP.

For the blockchain timestamp itself, two articles matter. Article 41(1) protects any electronic time stamp the same way: a court can't refuse it for being electronic or for not being qualified. Article 41(2) keeps the presumption of an accurate date and of integrity for qualified time stamps only, and article 42 sets that bar: a time source linked to UTC and a seal from a qualified trust service provider. A SKALE block time doesn't meet it, and Chaindoc doesn't sell it as one.

eIDAS 2.0 (Regulation 2024/1183) added electronic ledgers. Article 45k gives any ledger the same protection against being thrown out, and keeps the presumption of correct ordering and integrity for qualified ledgers, which only a QTSP can run under article 45l. SKALE is a ledger in the plain sense, not a qualified one. In Europe, then, the record is admissible, and how much it weighs is up to the judge.

In the US

The ESIGN Act (15 U.S.C. § 7001) and UETA give the signature its effect. For the evidence, Federal Rule of Evidence 902(14) lets data be self-authenticated through a "process of digital identification", certified by a qualified person, and the committee note to Rule 902 names hash values as the usual method. Arizona went a step further: A.R.S. § 44-7061 says a signature secured through blockchain technology is an electronic signature.

What a court still asks

Who controlled the email account. Whether the signer actually saw the document. Whether anyone pressured them. A hash answers none of that, which is the audit trail's job, and it's why we'd never pitch the chain as a replacement for one.

Plenty of sites sell digital notary services on blockchain, and the phrase borrows a word it hasn't earned. A notary checks who is in front of them, their capacity and their consent, and in many countries a notarial deed carries weight no private record gets. Blockchain notarization records that a hash existed. Useful, but different. If a transaction legally needs a notary, a blockchain timestamp won't stand in for one. Our guide to proving a fact with a notarial record covers when you need the real thing.

Search for SKALE and most of what comes back is the price of SKL, the network's staking token. You don't need it, or any other token, to sign or check a document in Chaindoc.

The SKALE network itself is a set of EVM-compatible chains that share one validator pool. Some chains belong to a single app. Others, like Calypso, Europa and Nebula, are public chains on Ethereum that many apps share. Because they run the Ethereum Virtual Machine, standard Ethereum tools can read what's written there, so the record isn't locked into a format only one vendor understands.

If you're weighing the SKALE blockchain for a product of your own, start with SKALE's developer documentation rather than this page. For a signer, one sentence covers it: SKALE is where the blockchain timestamp goes, and you'll never have to know more than that.

Most signed documents are never disputed, and for those the blockchain timestamp just sits there, costing nobody anything. It earns its keep in a narrower set of cases. A counterparty claims the version you hold isn't the one they signed. A contract outlives the tools that produced it, and the person checking it in ten years has never heard of Chaindoc. Someone in another country has to verify a document without an account in your systems. In each case the useful property is the same: the proof is public and doesn't depend on us.

It won't rescue a signature that was never valid, a signer who was misled, or a deal that the law reserves for a qualified signature or a notary. For those, read when a qualified signature is required and what an e-signature audit trail records first. If the trade-offs above suit you, compare the plans and send your next contract through Chaindoc. The blockchain timestamp comes with it.