You really should add timestamping to ArchiveBox. The easiest way to do that would be via my OpenTimestamps protocol, https://opentimestamps.org It's open source and free to use, and uses Bitcoin for the actual timestamps. Users of it do not need to make Bitcoin transactions themselves as a set of community calendar servers do that for you. You also don't need a Bitcoin node to create an OTS timestamp, and you can va…
We're going to add TLSNotary support for real cryptographic signing, see my comments below :) Timestamping is also on my roadmap, definitely as a plugin (and likely paid) as it's more corporate users that really need it. We need to keep some of the really advanced attestation features paid to be able to support the rest of the business.
Last I checked TLSNotary requires a trusted third party. I would strongly suggest timestamping TLSNotary evidence, to be able to prove that evidence was created prior to any of these trusted third parties being compromised.