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From: Kate Salazar <mercedes.catherine.salazar@gmail.com>
Date: Sat, 16 Oct 2021 23:34:32 +0200
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To: David Bakin <david@bakins-bits.com>, 
 Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
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Subject: Re: [bitcoin-dev] Year 2038 problem and year 2106 chain halting
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Hi, BIP 42 is a code base consensus soft fork that at the time of
activation does not really manifest as a fork because nobody is running any
code not already applying it. Can a similar thing be done in 17 years? (I
haven't really made sense of this year 2038 problem, I don't know or
understand what is required if there's something to be done).
Cheers!

On Sat, Oct 16, 2021 at 11:00 PM David Bakin via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> yes but ... just for the sake of argument ... if a change such as this
> wraparound interpretation is made anytime in the next 5 years it'll be ov=
er
> a *decade after that *before any wrapped-around timestamp is legitimately
> mined ... and by then nobody will be running incompatible (decade old) no=
de
> software (especially since it would mean that a decade had gone by withou=
t
> a *single* consensus change ... seems very unlikely).
>
> On Sat, Oct 16, 2021 at 11:57 AM vjudeu via bitcoin-dev <
> bitcoin-dev@lists.linuxfoundation.org> wrote:
>
>> > What happens if a series of blocks has a timestamp of 0xFFFFFFFF at th=
e
>> appropriate time?
>>
>> The chain will halt for all old clients, because there is no 32-bit valu=
e
>> greater than 0xffffffff.
>>
>> > 1. Is not violated, since "not lower than" means "greater than or equa=
l
>> to"
>>
>> No, because it has to be strictly "greater than" in the Bitcoin Core
>> source code, it is rejected when it is "lower or equal to", see:
>> https://github.com/bitcoin/bitcoin/blob/6f0cbc75be7644c276650fd98bfdb635=
8b827399/src/validation.cpp#L3089-L3094
>>
>> > 2. Is not violated, since it would be a past actual real time.
>>
>> If the current time is 0x0000000100000000, then the lowest 32 bits will
>> point to some time around 1970, so for old clients two rules are violate=
d
>> at the same time.
>>
>> > 3. Is not violated since 0xFFFFFFFF < 0x100000000.
>>
>> This is hard to change, because 32-bit timestamps are included in block
>> headers, so using any wider data type here will make it
>> hardware-incompatible and will cause a hard-fork. That's why I think new
>> timestamps should be placed in the coinbase transaction. But that still
>> does not solve chain halting problem.
>>
>> To test chain halting, all that is needed is starting regtest and
>> producing one block with 0xffffffff timestamp, just after the Genesis
>> Block. Then, median time is equal to 0xffffffff and adding any new block=
s
>> is no longer possible. The only soft-fork solution I can see require
>> overwriting that block.
>>
>> Example from https://bitcointalk.org/index.php?topic=3D5365359.0
>>
>> submitblock
>> 0100000006226e46111a0b59caaf126043eb5bbf28c34f3a5e332a1fc7b2b73cf188910f=
3663c0de115e2239e05df4df9c4bfa01b8e843aaf5dae590cac1d9bac0d44c0ffffffffffff=
f7f200100000001020000000001010000000000000000000000000000000000000000000000=
000000000000000000ffffffff03510101ffffffff0200f2052a010000001976a91462e907b=
15cbf27d5425399ebf6f0fb50ebb88f1888ac0000000000000000266a24aa21a9ede2f61c3f=
71d1defd3fa999dfa36953755c690689799962b48bebd836974e8cf90120000000000000000=
000000000000000000000000000000000000000000000000000000000
>> null
>> generatetoaddress 1 mpXwg4jMtRhuSpVq4xS3HFHmCmWp9NyGKt
>> CreateNewBlock: TestBlockValidity failed: time-too-old, block's timestam=
p
>> is too early (code -1)
>>
>> I don't know any timestamp that can be used in any next block and
>> accepted by old nodes.
>>
>> On 2021-10-16 01:01:54 user ZmnSCPxj <ZmnSCPxj@protonmail.com> wrote:
>> > Good morning yanmaani,
>>
>>
>> > It's well-known. Nobody really cares, because it's so far off. Not
>> > possible to do by softfork, no.
>>
>> I think it is possible by softfork if we try hard enough?
>>
>>
>> > 1.  The block timestamp may not be lower than the median of the last 1=
1
>> >     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)
>>
>> What happens if a series of blocks has a timestamp of 0xFFFFFFFF at the
>> appropriate time?
>>
>> In that case:
>>
>> 1.  Is not violated, since "not lower than" means "greater than or equal
>> to", and after a while the median becomes 0xFFFFFFFF and 0xFFFFFFFF =3D=
=3D
>> 0xFFFFFFFF
>> 2.  Is not violated, since it would be a past actual real time.
>> 3.  Is not violated since 0xFFFFFFFF < 0x100000000.
>>
>> In that case, we could then add an additional rule, which is that a
>> 64-bit (or 128-bit, or 256-bit) timestamp has to be present in the coinb=
ase
>> transaction, with similar rules except translated to 64-bit/128-bit/256-=
bit.
>>
>> Possibly a similar scheme could be used for `nLockTime`; we could put a
>> 64-bit `nLockTime64` in that additional signed block in Taproot SegWit v=
1
>> if the legacy v`nLockTime` is at the maximum seconds-timelock possible.
>>
>> Regards,
>> ZmnSCPxj
>>
>>
>> _______________________________________________
>> bitcoin-dev mailing list
>> bitcoin-dev@lists.linuxfoundation.org
>> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>

--000000000000843ca505ce7f142a
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr">Hi, BIP 42 is a code base consensus soft fork that at the =
time of activation does not really manifest as a fork because nobody is run=
ning any code not already applying it. Can a similar thing be done in 17 ye=
ars? (I haven&#39;t really made sense of this year 2038 problem, I don&#39;=
t know or understand what is required=C2=A0if there&#39;s something to be d=
one).<div>Cheers!</div></div><br><div class=3D"gmail_quote"><div dir=3D"ltr=
" class=3D"gmail_attr">On Sat, Oct 16, 2021 at 11:00 PM David Bakin via bit=
coin-dev &lt;<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org">bitco=
in-dev@lists.linuxfoundation.org</a>&gt; wrote:<br></div><blockquote class=
=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rg=
b(204,204,204);padding-left:1ex"><div dir=3D"ltr">yes but ... just for the =
sake of argument ... if a change such as this wraparound interpretation is =
made anytime in the next 5 years it&#39;ll be over a <i>decade after that=
=C2=A0</i>before any wrapped-around timestamp is legitimately mined ... and=
 by then nobody will be running incompatible (decade old) node software (es=
pecially since it would mean that a decade had gone by without a <i>single<=
/i>=C2=A0consensus=C2=A0change ... seems very unlikely).</div><br><div clas=
s=3D"gmail_quote"><div dir=3D"ltr" class=3D"gmail_attr">On Sat, Oct 16, 202=
1 at 11:57 AM vjudeu via bitcoin-dev &lt;<a href=3D"mailto:bitcoin-dev@list=
s.linuxfoundation.org" target=3D"_blank">bitcoin-dev@lists.linuxfoundation.=
org</a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"marg=
in:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1e=
x">&gt; What happens if a series of blocks has a timestamp of 0xFFFFFFFF at=
 the appropriate time?<br>
<br>
The chain will halt for all old clients, because there is no 32-bit value g=
reater than 0xffffffff.<br>
<br>
&gt; 1. Is not violated, since &quot;not lower than&quot; means &quot;great=
er than or equal to&quot;<br>
<br>
No, because it has to be strictly &quot;greater than&quot; in the Bitcoin C=
ore source code, it is rejected when it is &quot;lower or equal to&quot;, s=
ee: <a href=3D"https://github.com/bitcoin/bitcoin/blob/6f0cbc75be7644c27665=
0fd98bfdb6358b827399/src/validation.cpp#L3089-L3094" rel=3D"noreferrer" tar=
get=3D"_blank">https://github.com/bitcoin/bitcoin/blob/6f0cbc75be7644c27665=
0fd98bfdb6358b827399/src/validation.cpp#L3089-L3094</a><br>
<br>
&gt; 2. Is not violated, since it would be a past actual real time.<br>
<br>
If the current time is 0x0000000100000000, then the lowest 32 bits will poi=
nt to some time around 1970, so for old clients two rules are violated at t=
he same time.<br>
<br>
&gt; 3. Is not violated since 0xFFFFFFFF &lt; 0x100000000.<br>
<br>
This is hard to change, because 32-bit timestamps are included in block hea=
ders, so using any wider data type here will make it hardware-incompatible =
and will cause a hard-fork. That&#39;s why I think new timestamps should be=
 placed in the coinbase transaction. But that still does not solve chain ha=
lting problem.<br>
<br>
To test chain halting, all that is needed is starting regtest and producing=
 one block with 0xffffffff timestamp, just after the Genesis Block. Then, m=
edian time is equal to 0xffffffff and adding any new blocks is no longer po=
ssible. The only soft-fork solution I can see require overwriting that bloc=
k.<br>
<br>
Example from <a href=3D"https://bitcointalk.org/index.php?topic=3D5365359.0=
" rel=3D"noreferrer" target=3D"_blank">https://bitcointalk.org/index.php?to=
pic=3D5365359.0</a><br>
<br>
submitblock 0100000006226e46111a0b59caaf126043eb5bbf28c34f3a5e332a1fc7b2b73=
cf188910f3663c0de115e2239e05df4df9c4bfa01b8e843aaf5dae590cac1d9bac0d44c0fff=
ffffffffff7f200100000001020000000001010000000000000000000000000000000000000=
000000000000000000000000000ffffffff03510101ffffffff0200f2052a010000001976a9=
1462e907b15cbf27d5425399ebf6f0fb50ebb88f1888ac0000000000000000266a24aa21a9e=
de2f61c3f71d1defd3fa999dfa36953755c690689799962b48bebd836974e8cf90120000000=
000000000000000000000000000000000000000000000000000000000000000000<br>
null<br>
generatetoaddress 1 mpXwg4jMtRhuSpVq4xS3HFHmCmWp9NyGKt<br>
CreateNewBlock: TestBlockValidity failed: time-too-old, block&#39;s timesta=
mp is too early (code -1)<br>
<br>
I don&#39;t know any timestamp that can be used in any next block and accep=
ted by old nodes.<br>
<br>
On 2021-10-16 01:01:54 user ZmnSCPxj &lt;<a href=3D"mailto:ZmnSCPxj@protonm=
ail.com" target=3D"_blank">ZmnSCPxj@protonmail.com</a>&gt; wrote:<br>
&gt; Good morning yanmaani,<br>
<br>
<br>
&gt; It&#39;s well-known. Nobody really cares, because it&#39;s so far off.=
 Not<br>
&gt; possible to do by softfork, no.<br>
<br>
I think it is possible by softfork if we try hard enough?<br>
<br>
<br>
&gt; 1.=C2=A0 The block timestamp may not be lower than the median of the l=
ast 11<br>
&gt;=C2=A0 =C2=A0 =C2=A0blocks&#39;<br>
&gt;<br>
&gt; 2.=C2=A0 The block timestamp may not be greater than the current time =
plus two<br>
&gt;=C2=A0 =C2=A0 =C2=A0hours<br>
&gt;<br>
&gt; 3.=C2=A0 The block timestamp may not be greater than 2^32 (Sun, 07 Feb=
 2106<br>
&gt;=C2=A0 =C2=A0 =C2=A006:28:16 +0000)<br>
<br>
What happens if a series of blocks has a timestamp of 0xFFFFFFFF at the app=
ropriate time?<br>
<br>
In that case:<br>
<br>
1.=C2=A0 Is not violated, since &quot;not lower than&quot; means &quot;grea=
ter than or equal to&quot;, and after a while the median becomes 0xFFFFFFFF=
 and 0xFFFFFFFF =3D=3D 0xFFFFFFFF<br>
2.=C2=A0 Is not violated, since it would be a past actual real time.<br>
3.=C2=A0 Is not violated since 0xFFFFFFFF &lt; 0x100000000.<br>
<br>
In that case, we could then add an additional rule, which is that a 64-bit =
(or 128-bit, or 256-bit) timestamp has to be present in the coinbase transa=
ction, with similar rules except translated to 64-bit/128-bit/256-bit.<br>
<br>
Possibly a similar scheme could be used for `nLockTime`; we could put a 64-=
bit `nLockTime64` in that additional signed block in Taproot SegWit v1 if t=
he legacy v`nLockTime` is at the maximum seconds-timelock possible.<br>
<br>
Regards,<br>
ZmnSCPxj<br>
<br>
<br>
_______________________________________________<br>
bitcoin-dev mailing list<br>
<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" target=3D"_blank">=
bitcoin-dev@lists.linuxfoundation.org</a><br>
<a href=3D"https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev" =
rel=3D"noreferrer" target=3D"_blank">https://lists.linuxfoundation.org/mail=
man/listinfo/bitcoin-dev</a><br>
</blockquote></div>
_______________________________________________<br>
bitcoin-dev mailing list<br>
<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" target=3D"_blank">=
bitcoin-dev@lists.linuxfoundation.org</a><br>
<a href=3D"https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev" =
rel=3D"noreferrer" target=3D"_blank">https://lists.linuxfoundation.org/mail=
man/listinfo/bitcoin-dev</a><br>
</blockquote></div>

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