Re: Open Timestamps

Mountie - You bring up a good point.  Generating accurate timestamps can be
problematic if you are relying on any outside system.

In version 1.0 of Chainpoint <http://chainpoint.org> we included a
"timestamp" field that contained a non-authoritative Unix timestamp of the
target_hash.  Upon further consideration and feedback from customers, we
removed this field from the proof format.  We didn't like having a field
that didn't represent verifiable data. With Chainpoint 2.0, we use JSON-LD.
If you need accurate timestamps, you can include a trusted timestamp in the
data being represented by the targetHash, or you can embed a Chainpoint
proof inside a JSON-LD document that includes a trusted timestamp.

A hash calendar <https://en.wikipedia.org/wiki/Hash_calendar> is a type of
merkle tree that calculates a merkle root once per second has hashed are
continually added to the tree. This captures the state of the tree in one
second intervals.  Systems such as Guardtime's KSI
<https://eprint.iacr.org/2013/834.pdf> use a hash calendar to generate a
partial proof. They then aggregate all the merkle roots from the hash
calendar, construct a new merkle tree, anchor the merkle root in one or
more sources, extract the proof path for each item in the tree, and append
the partial proofs with the new data to generate the final proofs.  You can
build a system using a hash calendar that generates Chainpoint proofs.  Not
everyone requires this capability so we didn't build it into the base
protocol.

Accuracy in timestamping is important. For this reason, and others, I don't
consider Chainpoint to be a timestamping protocol. Instead, I think of it
as a proof protocol.

If this topic interests you, I hope you'll join the Chainpoint Community
Group <https://www.w3.org/community/chainpoint/>.

Wayne
----------

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On Fri, Sep 16, 2016 at 1:40 AM, Mountie Lee <mountie@paygate.net> wrote:

> how to handle time accuracy?
> existing timestamping service use atomic clock.
> in your document, seams out-of-scope.
> 2016년 9월 16일 (금) 00:05, Peter Todd <pete@petertodd.org>님이 작성:
>
>> On Thu, Sep 15, 2016 at 03:14:40PM +0200, Melvin Carvalho wrote:
>> > I thought I'd pass on some really interesting work from Peter Todd
>> (cc'd)
>> > entitled Open Timestamps
>> >
>> > https://petertodd.org/2016/opentimestamps-announcement
>> >
>> > It might be a great input to some of the work that is hoping to be
>> > standardized at the w3c
>>
>> Thanks!
>>
>> Yes, I absolutely do think a W3C standard would be appropriate for this,
>> once
>> it's gotten community peer review and usage.
>>
>> --
>> https://petertodd.org 'peter'[:-1]@petertodd.org
>>
>