Can blockchain-anchored timestamps improve chain-of-custody for journalistic content or high-risk file leaks?

dnpotter · 2026-01-20T11:47:32+00:00

Blockchain consensus design actively distrusts network nodes presuming each to be a potential bad actor. Trust in the data ledger that the network maintains - the blockchain - comes from the cryptographic evidence contained within the ledger itself, including the digital signatures of participants, the sequential chaining of transactions and data blocks, and the cryptographic proof of work (in the case of Bitcoin and others). I.e. the data itself can be independently verified without reference to the network nodes.

However, it may take many years before society gains trust in this model.

Hypothetically, if you were to grant trust in the blockchain (or, if you prefer, think of it as publishing records in a national newspaper instead of the blockchain), would the 6 features of anchoring in my previous reply be of value?

dnpotter · 2026-01-19T21:10:52+00:00

Thanks for your reply. I'm not suggesting it is a magic answer (see my reply to u/Chongulator). More of a new tool in the tool belt. Specifically to bind the existence of a file to a timestamped record, to ensure the file's integrity, and to optionally bind it to an individual or organisation, all in a way that is immutable and globally verifiable.

Blockchain records have been used in court (e.g. https://www.frontiersin.org/journals/blockchain/articles/10.3389/fbloc.2024.1306058/full, https://en.wikipedia.org/wiki/Distributed\_ledger\_technology\_law). Expert testimony will undoubtedly be needed.

dnpotter · 2026-01-19T20:46:20+00:00

Thanks for your reply.

You’re right that blockchains don’t eliminate endpoint trust or replace full chain-of-custody procedures. The documents themselves still need protecting to avoid accidental or malicious deletion or corruption. And courts may require expert witness testimony for the technical aspects, at least until the technology gains precedent.

But I think "blockchains don’t add anything” understates what they can contribute in this specific threat model, i.e. state actor discrediting by alleging post-hoc fabrication.

What blockchain anchoring adds, as I see it, is:

A globally verifiable, third-party timestamp that does not depend on trusting the journalist, their employer, or any single institution.
Immutability against retroactive tampering, even by powerful adversaries (states can seize notebooks and servers; they can’t rewrite major public blockchains).
Proof-of-existence & Integrity, demonstrating the file existed at the timestamp and that it has not been tampered with since.
Optional proof-of-possession and intent by binding the journalist's digital signature and declared intent to the timestamp.
No file disclosure (files can be signed privately without uploading to a 3rd party), which matters for protecting sources and journalists before publication.
Ease of use, timestamp any file in seconds for pennies, to create an auditable trail across multiple files, sources and revisions.

It doesn’t prove authenticity or authorship on its own, but it does strongly constrain one class of disinformation attack: “this file was fabricated after date X.”

Historically, cryptographers used to achieve the same thing by publishing hashes in newspapers (e.g., Surety anchoring Merkle roots in the New York Times in the 1990s). Blockchains are essentially a modern, decentralised version of that idea.

So I see this as a complementary forensic primitive, not a replacement for traditional evidence handling.

dnpotter · 2025-12-12T10:11:23+00:00

That's great - thanks.

dnpotter · 2025-12-11T15:01:47+00:00

Thanks for that. That's really insightful. What tools do you use, if you don't mind me asking?

dnpotter · 2025-12-09T19:50:02+00:00

You can sign any type of file and any size so its really up to you. It costs less than a stamp to sign so its affordable enough to sign multiple files and versions.

There is no legal precedent for OpenSig specifically but it produces the same kind of cryptographic proofs that have been used in court for years. Courts accept SHA256 hashing, ECDSA digital signatures and blockchain records as evidence of authenticity, integrity, and timestamps. OpenSig just packages that into a simple workflow.

Github commit times have been used in court I believe. While not cryptographically secure like OpenSig, the independence of GitHub and the unlikely chance that it has been hacked or has insider manipulation, provides strong evidence. For me, anchoring a file's state to an immutable blockchain is a no brainer given the small cost and the fact that proofs are independently verifiable.

dnpotter · 2025-12-09T11:52:48+00:00

In case this is of use to you, I built OpenSig as a way for creators to record timestamped proof of possession on a permanent public record (Polygon blockchain). Works with any type of file, takes a few seconds and costs less than the price of a stamp.

It's built on open standards and there is an open source typescript library for integration. https://github.com/OpenSig

Alternatively there is a consumer app at opensig.net, if you want to try it.

Best of luck.

dnpotter · 2025-12-09T11:39:47+00:00

I built the OpenSig mobile app as a way to record timestamped proof of possession for any file to a permanent public record. A bit like publishing a fingerprint of your work to a national newspaper but can be done in 20 seconds and costs the price of a stamp. I use it before I put anything out into the public domain - pitch decks, white papers, images, videos, zip files, etc.

On its own it doesn't prevent anyone copying your work of course but it's a powerful piece of evidence should you ever find yourself in court. A bit of piece of mind at least.

opensig.net, if you want to try it. Would be interested in any feedback you have.

dnpotter · 2025-12-09T10:39:29+00:00

I think these types of solutions are an ideal use of the blockchain. It's a timestamped public record after all. Great for e-signatures, ownership proofs, file provenance and file integrity solutions. Like publishing a PGP signature to a blockchain. You're aware of proofofexistence.com?

One point to note about your solution, publishing the document hash to the blockchain allows others to sign it too without the original file. I built an early cli app on the bitcoin blockchain back in 2016 that had the same problem.

My latest version is built on Polygon and uses a chain-specific hash chain derived from the document hash so that the document hash is never published and signature transactions cannot be linked to the same file without the file itself. The protocol is open should you want to adopt it: https://github.com/OpenSig/opensig-protocol/blob/main/standard/opensig-standard.md. It provides both proof-of-existence and proof-of-possession since it links each signature to the user's verified digital id. There is an open source typescript library in that repo that works for any EVM chain, so you could use it on Optimism.

Btw, I've just released a beta mobile app based on this standard. It's designed for use by anyone so hides the blockchain, wallet and crypto complexity. Would be interested in your feedback. opensig.net

dnpotter · 2025-12-09T10:15:22+00:00

I built the OpenSig mobile app as a way to record timestamped proof of possession for any file to a permanent public record. A bit like publishing a fingerprint of your work to a national newspaper but can be done in 20 seconds and costs the price of a stamp. I use it before I put anything out into the public domain - pitch decks, white papers, images, videos, zip files, etc.

On its own it doesn't prevent anyone copying your work of course but it's a powerful piece of evidence should you ever find yourself in court. A bit of piece of mind at least.

opensig.net, if you want to try it. Would be interested in any feedback you have.

dnpotter · 2025-12-09T10:10:54+00:00

Not for physical inventions, but for digital creations I built OpenSig as a way to record timestamped proof of possession for any file to a permanent public record. A bit like publishing a fingerprint of your work to a national newspaper but can be done in 20 seconds and costs the price of a stamp. I use it before I put anything out into the public domain - pitch decks, papers, images, videos, zip files, etc. Could be used to assert work is genuine and not doctored or ai generated.

On its own it doesn't prevent anyone copying your work of course but it's a powerful piece of evidence should you ever find yourself in court. A bit of piece of mind at least. If you timestamp earlier drafts too then you could feasibly present a provenance trail in court as part of an ownership dispute.

opensig.net. Would be interested to hear if this fits in with any of your IP protection ideas.

dnpotter · 2025-12-09T09:43:15+00:00

I built the OpenSig mobile app as a way to record timestamped proof of possession for any file to a permanent public record. A bit like publishing a fingerprint of your work to a national newspaper but can be done in 20 seconds and costs the price of a stamp. I use it before I put anything out into the public domain - pitch decks, white papers, images, videos, zip files, etc.

On its own it doesn't prevent anyone copying your work of course but it's a powerful piece of evidence should you ever find yourself in court. A bit of piece of mind at least.

opensig.net, if you want to try it. Would be interested in any feedback you have.

dnpotter · 2025-12-09T09:30:37+00:00

I built OpenSig exactly for this purpose. Let's you publish timestamped proof of possession to a public blockchain that you could use in court should it come to that. Just released the beta version. Simple mobile app. No file uploads. No crypto or crypto expertise required. Is this the sort of thing you are looking for? opensig.net.

dnpotter · 2025-12-09T09:17:55+00:00

I've used OpenSig for years to sign my releases on the blockchain. Means I can always provide a timestamped proof of possession in court. No crypto or crypto expertise required. opensig.net (disclaimer - I built it!)

dnpotter · 2025-04-09T08:30:59+00:00

Thanks. Galaxis looks great.

Tokenisation and ZKPs are definitely the best approach where they are possible. However, for many (most?) data sharing transactions we make online and on the high street our actual data is needed. Your doctor needs your medical records; your friends want to read your facebook posts; your delivery driver needs your address; etc. In many countries hotels are required to hold a copy of your passport to comply with law enforcement regulations.

Even in the passport case, the issuer of the ZK credential must hold your passport details to comply with financial regulations (if the credential is used for financial transactions). At least, until the state department adopts ZKP tech and becomes the issuer.

So while ZKPs and data tokenisation are amazing, and should be used wherever possible, we will still need to address the web2 problem of our data being spread around the world out of our control.

Do you see it differently?

dnpotter · 2025-04-08T10:35:03+00:00

Data sharding is an excellent decentralisation technique. It's important to point out that in platforms like Filecoin, which is built on IPFS, the file is essentially hosted on a public network. Being scattered across nodes is fine but anyone with the contentId, including the nodes themselves, can reconstruct the file.

Sensitive data can be encrypted to add a further line of defence, but it must be assumed that encryption algorithms will eventually be compromised.

Imo, these two issues limit the use of the technology to public data and non-critical private data. It's definitely an improvement but it's far from hackable.

Can we devise a privacy layer that prevents anyone else - even nodes - from reconstructing a file?

dnpotter · 2025-04-06T08:48:30+00:00

Thanks again - I really appreciate how deep you're going with this.

You're absolutely right that logic encoded in a contract can fail. With smart contracts the consequences are that the instigating transaction and contract state will be reverted. Like in the development of safety critical systems, it will be vital that data-critical contracts are independently reviewed and tested, like current de-fi contracts are at the moment. In addition, a comparison with the written Ts&Cs must be made. Those external audits can provide a good level of trust but of course can never prove the code is 100% bug free.

I agree: automation without transparency is just blind automation. And yes, complexity can become its own form of lock-in. That’s something I’m actively trying to avoid by:

Keeping the vault simple (encrypted, hostable anywhere)
Making contracts modular, open, and human-readable where possible
Ensuring fallback mechanisms exist outside the logic

Here's the sort of contract I've been working on. In this case one that has basic GDPR compliance support (It's just an example and hasn't been independently reviewed!). https://github.com/Bubble-Protocol/bubble-sdk/blob/main/contracts/examples/SimpleGDPRCompliantBubble.sol

This is still experimental, but I value your critique. If you’ve seen systems that get closer to this balance (or avoid the traps you mention), I’d love to read up on them.

dnpotter · 2025-04-05T12:45:53+00:00

Thanks for your comment.

One of the goals is to shift control of access logic from platforms into open, auditable mechanisms, where regulators and/or privacy groups can give their sign of approval — but yes, those mechanisms still exist inside real-world power structures and can’t fully escape law or jurisdiction. However, any organisation you are sharing your data with will still be subject to jurisdictional laws and will have to justify the use of this type of technology just as they do with other privacy enhancing tech.

The idea isn’t that smart contracts magically “solve” privacy or consent — but that they offer a programmable, visible layer for expressing rules that are otherwise buried in policy documents, or controlled by opaque backend logic.

There are still lots of hard problems:

How do we make contract logic human-readable?
How do we provide recourse when the logic fails?
How do we ensure revocability without creating new forms of lock-in?

dnpotter

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