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From: Mark Friedenbach <mark@friedenbach.org>
Date: Thu, 27 Aug 2015 16:32:55 -0700
Message-ID: <CAOG=w-tuFtX2t+0FVfkoObw_a9-7j4LwX87YJU1n7adYu=DMdQ@mail.gmail.com>
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Subject: Re: [bitcoin-dev] [BIP-draft] CHECKSEQUENCEVERIFY - An opcode for
relative locktime
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So I've created 2 new repositories with changed rules regarding
sequencenumbers:
https://github.com/maaku/bitcoin/tree/sequencenumbers2
This repository inverts (un-inverts?) the sequence number. nSequence=3D1
means 1 block relative lock-height. nSequence=3DLOCKTIME_THRESHOLD means 1
second relative lock-height. nSequence>=3D0x80000000 (most significant bit
set) is not interpreted as a relative lock-time.
https://github.com/maaku/bitcoin/tree/sequencenumbers3
This repository not only inverts the sequence number, but also interprets
it as a fixed-point number. This allows up to 5 year relative lock times
using blocks as units, and saves 12 low-order bits for future use. Or, up
to about 2 year relative lock times using seconds as units, and saves 4
bits for future use without second-level granularity. More bits could be
recovered from time-based locktimes by choosing a higher granularity (a
soft-fork change if done correctly).
On Tue, Aug 25, 2015 at 3:08 PM, Mark Friedenbach <mark@friedenbach.org>
wrote:
> To follow up on this, let's say that you want to be able to have up to 1
> year relative lock-times. This choice is somewhat arbitrary and what I
> would like some input on, but I'll come back to this point.
>
> * 1 bit is necessary to enable/disable relative lock-time.
>
> * 1 bit is necessary to indicate whether seconds vs blocks as the unit o=
f
> measurement.
>
> * 1 year of time with 1-second granularity requires 25 bits. However
> since blocks occur at approximately 10 minute intervals on average, havin=
g
> a relative lock-time significantly less than this interval doesn't make
> much sense. A granularity of 256 seconds would be greater than the Nyquis=
t
> frequency and requires only 17 bits.
>
> * 1 year of blocks with 1-block granularity requires 16 bits.
>
> So time-based relative lock time requires about 19 bits, and block-based
> relative lock-time requires about 18 bits. That leaves 13 or 14 bits for
> other uses.
>
> Assuming a maximum of 1-year relative lock-times. But what is an
> appropriate maximum to choose? The use cases I have considered have only
> had lock times on the order of a few days to a month or so. However I wou=
ld
> feel uncomfortable going less than a year for a hard maximum, and am havi=
ng
> trouble thinking of any use case that would require more than a year of
> lock-time. Can anyone else think of a use case that requires >1yr relativ=
e
> lock-time?
>
> TL;DR
>
> On Sun, Aug 23, 2015 at 7:37 PM, Mark Friedenbach <mark@friedenbach.org>
> wrote:
>
>> A power of 2 would be far more efficient here. The key question is how
>> long of a relative block time do you need? Figure out what the maximum
>> should be ( I don't know what that would be, any ideas?) and then see ho=
w
>> many bits you have left over.
>> On Aug 23, 2015 7:23 PM, "Jorge Tim=C3=B3n" <
>> bitcoin-dev@lists.linuxfoundation.org> wrote:
>>
>>> On Mon, Aug 24, 2015 at 3:01 AM, Gregory Maxwell via bitcoin-dev
>>> <bitcoin-dev@lists.linuxfoundation.org> wrote:
>>> > Seperately, to Mark and Btcdrank: Adding an extra wrinkel to the
>>> > discussion has any thought been given to represent one block with mor=
e
>>> > than one increment? This would leave additional space for future
>>> > signaling, or allow, for example, higher resolution numbers for a
>>> > sharechain commitement.
>>>
>>> No, I don't think anybody thought about this. I just explained this to
>>> Pieter using "for example, 10 instead of 1".
>>> He suggested 600 increments so that it is more similar to timestamps.
>>> _______________________________________________
>>> bitcoin-dev mailing list
>>> bitcoin-dev@lists.linuxfoundation.org
>>> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>>>
>>
>
--001a113f9694224806051e536422
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Content-Transfer-Encoding: quoted-printable
<div dir=3D"ltr"><div><div>So I've created 2 new repositories with chan=
ged rules regarding sequencenumbers:<br><br><a href=3D"https://github.com/m=
aaku/bitcoin/tree/sequencenumbers2">https://github.com/maaku/bitcoin/tree/s=
equencenumbers2</a><br><br></div>This repository inverts (un-inverts?) the =
sequence number. nSequence=3D1 means 1 block relative lock-height. nSequenc=
e=3DLOCKTIME_THRESHOLD means 1 second relative lock-height. nSequence>=
=3D0x80000000 (most significant bit set) is not interpreted as a relative l=
ock-time.<br><br><a href=3D"https://github.com/maaku/bitcoin/tree/sequencen=
umbers3">https://github.com/maaku/bitcoin/tree/sequencenumbers3</a><br><br>=
</div>This repository not only inverts the sequence number, but also interp=
rets it as a fixed-point number. This allows up to 5 year relative lock tim=
es using blocks as units, and saves 12 low-order bits for future use. Or, u=
p to about 2 year relative lock times using seconds as units, and saves 4 b=
its for future use without second-level granularity. More bits could be rec=
overed from time-based locktimes by choosing a higher granularity (a soft-f=
ork change if done correctly).<br></div><div class=3D"gmail_extra"><br><div=
class=3D"gmail_quote">On Tue, Aug 25, 2015 at 3:08 PM, Mark Friedenbach <s=
pan dir=3D"ltr"><<a href=3D"mailto:mark@friedenbach.org" target=3D"_blan=
k">mark@friedenbach.org</a>></span> wrote:<br><blockquote class=3D"gmail=
_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:=
1ex"><div dir=3D"ltr"><div><div>To follow up on this, let's say that yo=
u want to be able to have up to 1 year relative lock-times. This choice is =
somewhat arbitrary and what I would like some input on, but I'll come b=
ack to this point.<br><br></div><div>=C2=A0* 1 bit is necessary to enable/d=
isable relative lock-time.<br></div><div><br></div><div>=C2=A0* 1 bit is ne=
cessary to indicate whether seconds vs blocks as the unit of measurement.<b=
r><br></div><div>=C2=A0* 1 year of time with 1-second granularity requires =
25 bits. However since blocks occur at approximately 10 minute intervals on=
average, having a relative lock-time significantly less than this interval=
doesn't make much sense. A granularity of 256 seconds would be greater=
than the Nyquist frequency and requires only 17 bits.<br><br></div><div>=
=C2=A0* 1 year of blocks with 1-block granularity requires 16 bits.<br></di=
v><div><br></div>So time-based relative lock time requires about 19 bits, a=
nd block-based relative lock-time requires about 18 bits. That leaves 13 or=
14 bits for other uses.<br><br></div><div>Assuming a maximum of 1-year rel=
ative lock-times. But what is an appropriate maximum to choose? The use cas=
es I have considered have only had lock times on the order of a few days to=
a month or so. However I would feel uncomfortable going less than a year f=
or a hard maximum, and am having trouble thinking of any use case that woul=
d require more than a year of lock-time. Can anyone else think of a use cas=
e that requires >1yr relative lock-time?<br></div><div><br></div>TL;DR <=
br></div><div class=3D"HOEnZb"><div class=3D"h5"><div class=3D"gmail_extra"=
><br><div class=3D"gmail_quote">On Sun, Aug 23, 2015 at 7:37 PM, Mark Fried=
enbach <span dir=3D"ltr"><<a href=3D"mailto:mark@friedenbach.org" target=
=3D"_blank">mark@friedenbach.org</a>></span> wrote:<br><blockquote class=
=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padd=
ing-left:1ex"><p dir=3D"ltr">A power of 2 would be far more efficient here.=
The key question is how long of a relative block time do you need? Figure =
out what the maximum should be ( I don't know what that would be, any i=
deas?) and then see how many bits you have left over.</p><div><div>
<div class=3D"gmail_quote">On Aug 23, 2015 7:23 PM, "Jorge Tim=C3=B3n&=
quot; <<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" target=
=3D"_blank">bitcoin-dev@lists.linuxfoundation.org</a>> wrote:<br type=3D=
"attribution"><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;=
border-left:1px #ccc solid;padding-left:1ex">On Mon, Aug 24, 2015 at 3:01 A=
M, Gregory Maxwell via bitcoin-dev<br>
<<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" target=3D"_bla=
nk">bitcoin-dev@lists.linuxfoundation.org</a>> wrote:<br>
> Seperately, to Mark and Btcdrank: Adding an extra wrinkel to the<br>
> discussion has any thought been given to represent one block with more=
<br>
> than one increment?=C2=A0 This would leave additional space for future=
<br>
> signaling, or allow, for example, higher resolution numbers for a<br>
> sharechain commitement.<br>
<br>
No, I don't think anybody thought about this. I just explained this to<=
br>
Pieter using "for example, 10 instead of 1".<br>
He suggested 600 increments so that it is more similar to timestamps.<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>
</div></div></blockquote></div><br></div>
</div></div></blockquote></div><br></div>
--001a113f9694224806051e536422--
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