On Mon, Jan 29, 2018 at 09:54:23PM +0000, Gregory Maxwell via bitcoin-dev wrote:
> If times need to be accurate Bitcoin would need to use a rather
> different design (e.g. each block would commit to the observation time
> of the prior N blocks, and an iterative algorithm would solve for each
> blocks time and each miners local offset).
> 
> IIRC open-timestamp calendar servers provide more precise
> time-stamping under the assumption that the calendar server is
> behaving correctly.

That is incorrect. The OpenTimestamps servers are specifically designed not to
be trusted, and thus do not make any cryptographically verifiable attestations
as to when timestamps were created.

In the future I expect to add a trusted timestamping scheme via disposable keys
to the OpenTimestamps protocol, but that work isn't yet complete:

https://lists.opentimestamps.org/pipermail/ots-dev/2017-May/000001.html

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https://petertodd.org 'peter'[:-1]@petertodd.org