The Bitcoin blockchain requires mining to solve double-spend - it's computationally infeasible to convince some subset of the network that you're spending a coi

The Bitcoin blockchain requires mining to solve double-spend - it's computationally infeasible to convince some subset of the network that you're spending a coin in one way, and also another subset of the network that you're spending the same coin in a different way. Notarization doesn't have a double-spend problem because there's no concept of "spending" - if you get the same document notarized by multiple people, that's perfectly fine. And because of that, you don't have a centralized authority problem. If you don't think people trust Cloudflare, have other Roughtime services sign your message. Each one adds additional confidence that the message was seen before a certain time. (Because you don't need mining to solve double-spend, you can do this without the effective requirement that any trustworthy Bitcoin-style blockchain must consume a significant fraction of computational power / useful energy in the known universe.)