> It should not [take?] 20 minutes either. Fair enough; the tech I know and mentioned (OpenTimestamps) is tied indirectly to Bitcoin's blockchain confirmation

> It should not [take?] 20 minutes either. Fair enough; the tech I know and mentioned (OpenTimestamps) is tied indirectly to Bitcoin's blockchain confirmation speed, thus both slow-ish, and also probabilistic rather than guaranteed. On the other hand, it gives good assurance that the tool will be around for a long time, and able to survive any single service provider's failure. > The crypto involved should be pretty trivial. Depends on the requirements. The tech I know and use (OTS) is privacy-conscious and handles timestamping of documents without revealing their actual content. Instead you submit hash(hash(document) + random, private IV) [1], which provides for both anonymous use, and ability to keep the signed content private, as the signed hash cannot be directly tied to any plaintext. This isn't strictly necessary for publicly-posted web pages, but certainly is useful for private documents, security-sensitive documents, etc. All in all, it's a starting point. Another possible approach would be to standardize submission to, and verification through a service like https://archive.is/ https://archive.is/, but that puts all trust into one 3rd party. > Input: [plain]text Directly timestamping the plaintext fails badly if the timestamping service provider is dishonest and creates an earlier timestamp for the content in their name, only to turn around and accuse the author of stealing the content. Or - a slightly paranoid scenario, but probably warranted in the post-Snowden era - if a whistleblower tries to timestamp some materials before distribution, but the timestamping service provider's filters catch the document and instead alert the government. Ergo, I'd prefer a blind timestamp, with the ability to reveal at the discretion of the author or whistleblower, even at the cost of more complex workflow. [1] sadly this means the author needs to keep a file containing the IV and a bit of other metadata.