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The roughtime protocol gives a secure timestamp right now. Can it be used as a timestamp authority, to sign a document and later prove that it existed before a certain time?

joeforker
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The simplest way would be to just use a cryptographic hash of your file as a nounce in your request to the roughtime servers.

Somebody apparently even implemented a proof of concept, including a more sophisticated method.

Delphinator
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  • URL of that blog post has changed; https://blog.merovius.de/posts/2018-10-10-using-roughtime-as-a-cryptographic-notary/ is now current. – chrysn Jul 05 '23 at 09:13