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Date: Sun, 17 Oct 2021 15:14:41 +0000
From: yanmaani@cock.li
To: vjudeu@gazeta.pl
In-Reply-To: <143289360-eb35e705fded3eb4175a6f8d7669b3a0@pmq5v.m5r2.onet>
References: <143289360-eb35e705fded3eb4175a6f8d7669b3a0@pmq5v.m5r2.onet>
Message-ID: <0d0b22a297d112939e11c86aa1f6d736@cock.li>
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Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Year 2038 problem and year 2106 chain halting
Precedence: list

What, no. The `k` value is calculated implicitly, because there's only 
one value of it that could ever be valid - if `k` is 1 too small, we're 
70 years too far back, and then the block will violate median of last 
11. If `k` is 1 too large, we're 70 years too far in the future, then 
the block will violate 2 hour rule. Nothing is added to coinbase or 
anywhere else.

It's possible that you'd need some extra logic for locktime, yes, but it 
would only be a problem in very special cases. Worst-case, you'll have 
to use block time locking in the years around the switch, or softfork in 
64-bit locking.

But unless I'm missing something, 32-bit would be enough, you just 
wouldn't be able to locktime something past the timestamp for the 
switch. After the switchover, everything would be back to normal.

This is a hardfork, yes, but it's a hardfork that kicks in way into the 
future. And because it's a hardfork, you might as well do anything, as 
long as it doesn't change anything now.

On 2021-10-15 22:22, vjudeu@gazeta.pl wrote:
> Your solution seems to solve the problem of chain halting, but there
> are more issues. For example: if you have some time modulo 2^32, then
> you no longer know if timestamp zero is related to 1970 or 2106 or
> some higher year. Your "k" value representing in fact the most
> significant 32 bits of 64-bit timestamp has to be stored in all cases
> where time is used. If there is no "k", then zero should be used for
> backward compatibility. Skipping "k" could cause problems related to
> OP_CHECKLOCKTIMEVERIFY or nLockTime, because if some transaction was
> timestamped to 0xbadc0ded, then that transaction will be valid in
> 0x00000000badc0ded, invalid in 0x0000000100000000, and valid again in
> 0x00000001badc0ded, the same for timelocked outputs.
> 
> So, I think your "k" value should be added to the coinbase
> transaction, then you can combine two 32-bit values, the lower bits
> from the block header and the higher bits from the coinbase
> transaction. Also, adding your "k" value transaction nLockTime field
> is needed (maybe in a similar way as transaction witness was added in
> Segwit), because in other case after reaching 0x0000000100000000 all
> off-chain transactions with timelocks around 0x00000000ffffffff will
> be additionally timelocked for the next N years. The same is needed
> for each OP_CHECKLOCKTIMEVERIFY, maybe pushing high 32 bits before the
> currently used value will solve that (and assuming zero if there is
> only some 32-bit value).