Date: Fri, 16 Oct 2020 21:58:20 +0000
To: "yanmaani@cock.li" <yanmaani@cock.li>,
 Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
From: Pieter Wuille <bitcoin-dev@wuille.net>
Reply-To: Pieter Wuille <bitcoin-dev@wuille.net>
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Subject: Re: [bitcoin-dev] Suggestion: Solve year 2106 problem by taking
	timestamps mod 2^32
Precedence: list

On Saturday, September 19, 2020 5:36 AM, yanmaani--- via bitcoin-dev <bitco=
in-dev@lists.linuxfoundation.org> wrote:

> Currently, Bitcoin's timestamp rules are as follows:
>
> 1.  The block timestamp may not be lower than the median of the last 11
>     blocks'
>
> 2.  The block timestamp may not be greater than the current time plus two
>     hours
>
> 3.  The block timestamp may not be greater than 2^32 (Sun, 07 Feb 2106
>     06:28:16 +0000)
>
>     Thus, Bitcoin will "die" on or about 2106-02-07, when there is no
>     timestamp below 2^32 that exceeds the median of the last 11 blocks.
>
>     If the rules were changed to the following, this problem would be
>     solved:
>
> 4.  The block timestamp plus k*2^32 may not be lower than the median of
>     the last 11 blocks'
>
> 5.  The block timestamp plus k*2^32 may not be greater than the current
>     time plus two hours
>
> 6.  k is an integer, whose value must be the same for the calculations of
>     Rule 1 and Rule 2

I believe that is equivalent to: we treat block headers (as abstract data
structure) as having a 64-bit timestamp, which have the requirement that
the difference between the timestamp and the median timestamp of the past 1=
1
blocks is at least one and at most 2^32 (I don't think we need to support
less than 6 blocks per 136 years).

On serialization, only the lower 32 bit are encoded. On deserialization,
the higher 32 bits are set equal to that of the median of the past 11 block=
s.
If that violates the rule above, set it one higher.

That's in line of how I'd expect this will eventually be addressed. There i=
s
no rush, of course.

>     What do you think of this idea? Is it worth a BIP?

Probably, at some point.

Cheers,

--
Pieter