Subject: Re: [bitcoin-dev] Why OpenTimestamps does not "linearize" its transactions

From: Peter Todd <[email-masked]>
Date: Tue, 14 Jun 2022 11:34:36 -0400

On Tue, Jun 14, 2022 at 08:45:43AM -0400, Undiscussed Horrific Abuse, One Victim of Many via bitcoin-dev wrote:
> > The basic service that a timestamp service provides is “this content (or at
> > least a digest of this content) existed at least as early as this
> > timestamp.” It says nothing about how long before the timestamp the content
> 
> OTS needlessly adds the requirement that the user publicize their .ots
> files to everybody who will make use of the timestamp.
>
> This does not provide the service you describe. It would be trivial to
> include enough cryptographic information in the original OP_RETURN, so
> as to obviate the need for publicizing the .ots file.

That approach does not scale. Via merkle trees, the OpenTimestamps system
routinely timestamps tens of thousands of messages with a single transaction:

https://petertodd.org/2016/opentimestamps-announcement#scalability-through-aggregation

Client-side validated .ots files are a necessary requirement to achieve this
scalability.

FWIW the most I've personally done is timestamped 750 million items from the
Internet Archive with a single transaction.

> If I send my .ots file to another party, a 4th party can replace it
> with their own, because there is no cryptographic pinning ensuring its
> contents. This changes the timestamp to one later, no longer proving
> the earliness of the data.

They can also simply delete their copy of the data, making it impossible to
prove anything about it.

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