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From: Btc Drak <btcdrak@gmail.com>
Date: Wed, 16 Sep 2015 23:40:06 +0100
Message-ID: <CADJgMzsPrg7VhTQC8aCvcQ3yAN8rtt+Qv_yfrCKMqOALpGPVyg@mail.gmail.com>
To: Mark Friedenbach <mark@friedenbach.org>
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Subject: Re: [bitcoin-dev] [BIP-draft] CHECKSEQUENCEVERIFY - An opcode for
relative locktime
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Where do we stand now on which sequencenumbers variation to use? We really
should make a decision now.
On Fri, Aug 28, 2015 at 12:32 AM, Mark Friedenbach via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:
> 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 bi=
t
> 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
>> of measurement.
>>
>> * 1 year of time with 1-second granularity requires 25 bits. However
>> since blocks occur at approximately 10 minute intervals on average, havi=
ng
>> a relative lock-time significantly less than this interval doesn't make
>> much sense. A granularity of 256 seconds would be greater than the Nyqui=
st
>> 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 wo=
uld
>> feel uncomfortable going less than a year for a hard maximum, and am hav=
ing
>> 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 relati=
ve
>> 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 h=
ow
>>> 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 mo=
re
>>>> > 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
>>>>
>>>
>>
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
>
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Content-Type: text/html; charset=UTF-8
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<div dir=3D"ltr">Where do we stand now on which=C2=A0sequencenumbers variat=
ion to use? We really should make a decision now.</div><div class=3D"gmail_=
extra"><br><div class=3D"gmail_quote">On Fri, Aug 28, 2015 at 12:32 AM, Mar=
k Friedenbach via bitcoin-dev <span dir=3D"ltr"><<a href=3D"mailto:bitco=
in-dev@lists.linuxfoundation.org" target=3D"_blank">bitcoin-dev@lists.linux=
foundation.org</a>></span> wrote:<br><blockquote class=3D"gmail_quote" s=
tyle=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div=
dir=3D"ltr"><div><div>So I've created 2 new repositories with changed =
rules regarding sequencenumbers:<br><br><a href=3D"https://github.com/maaku=
/bitcoin/tree/sequencenumbers2" target=3D"_blank">https://github.com/maaku/=
bitcoin/tree/sequencenumbers2</a><br><br></div>This repository inverts (un-=
inverts?) the sequence number. nSequence=3D1 means 1 block relative lock-he=
ight. nSequence=3DLOCKTIME_THRESHOLD means 1 second relative lock-height. n=
Sequence>=3D0x80000000 (most significant bit set) is not interpreted as =
a relative lock-time.<br><br><a href=3D"https://github.com/maaku/bitcoin/tr=
ee/sequencenumbers3" target=3D"_blank">https://github.com/maaku/bitcoin/tre=
e/sequencenumbers3</a><br><br></div>This repository not only inverts the se=
quence 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-or=
der bits for future use. Or, up to about 2 year relative lock times using s=
econds as units, and saves 4 bits for future use without second-level granu=
larity. More bits could be recovered from time-based locktimes by choosing =
a higher granularity (a soft-fork change if done correctly).<br></div><div =
class=3D"HOEnZb"><div class=3D"h5"><div class=3D"gmail_extra"><br><div clas=
s=3D"gmail_quote">On Tue, Aug 25, 2015 at 3:08 PM, Mark Friedenbach <span d=
ir=3D"ltr"><<a href=3D"mailto:mark@friedenbach.org" target=3D"_blank">ma=
rk@friedenbach.org</a>></span> wrote:<br><blockquote class=3D"gmail_quot=
e" 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 you wan=
t to be able to have up to 1 year relative lock-times. This choice is somew=
hat arbitrary and what I would like some input on, but I'll come back t=
o this point.<br><br></div><div>=C2=A0* 1 bit is necessary to enable/disabl=
e relative lock-time.<br></div><div><br></div><div>=C2=A0* 1 bit is necessa=
ry to indicate whether seconds vs blocks as the unit of measurement.<br><br=
></div><div>=C2=A0* 1 year of time with 1-second granularity requires 25 bi=
ts. However since blocks occur at approximately 10 minute intervals on aver=
age, having a relative lock-time significantly less than this interval does=
n'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></div><div>=
<br></div>So time-based relative lock time requires about 19 bits, and bloc=
k-based relative lock-time requires about 18 bits. That leaves 13 or 14 bit=
s for other uses.<br><br></div><div>Assuming a maximum of 1-year relative l=
ock-times. But what is an appropriate maximum to choose? The use cases I ha=
ve considered have only had lock times on the order of a few days to a mont=
h or so. However I would feel uncomfortable going less than a year for a ha=
rd maximum, and am having trouble thinking of any use case that would requi=
re more than a year of lock-time. Can anyone else think of a use case that =
requires >1yr relative lock-time?<br></div><div><br></div>TL;DR <br></di=
v><div><div><div class=3D"gmail_extra"><br><div class=3D"gmail_quote">On Su=
n, Aug 23, 2015 at 7:37 PM, Mark Friedenbach <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;padding-left:1ex"><p dir=3D"ltr">A power=
of 2 would be far more efficient here. The key question is how long of a r=
elative block time do you need? Figure out what the maximum should be ( I d=
on't know what that would be, any ideas?) and then see how many bits yo=
u 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>
</div></div><br>_______________________________________________<br>
bitcoin-dev mailing list<br>
<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org">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>
<br></blockquote></div><br></div>
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