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From: Eric Lombrozo <elombrozo@gmail.com>
Date: Wed, 16 Sep 2015 19:23:18 -0400
To: Btc Drak <btcdrak@gmail.com>,
Btc Drak via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org>,
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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I'd rather replace the whole nSequence thing with an explicit relative locktime with clear semantics...but I'm not going to fight this one too much.
On September 16, 2015 6:40:06 PM EDT, Btc Drak via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> wrote:
>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=1
>> means 1 block relative lock-height. nSequence=LOCKTIME_THRESHOLD
>means 1
>> second relative lock-height. nSequence>=0x80000000 (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
>>> of measurement.
>>>
>>> * 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.
>>>
>>> * 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 would
>>> feel uncomfortable going less than a year for a hard maximum, and am
>having
>>> 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
>relative
>>> 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 how
>>>> many bits you have left over.
>>>> On Aug 23, 2015 7:23 PM, "Jorge Timón" <
>>>> 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 more
>>>>> > 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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<html><head></head><body>I'd rather replace the whole nSequence thing with an explicit relative locktime with clear semantics...but I'm not going to fight this one too much.<br><br><div class="gmail_quote">On September 16, 2015 6:40:06 PM EDT, Btc Drak via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> wrote:<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<div dir="ltr">Where do we stand now on which sequencenumbers variation to use? We really should make a decision now.</div><div class="gmail_extra"><br /><div class="gmail_quote">On Fri, Aug 28, 2015 at 12:32 AM, Mark Friedenbach via bitcoin-dev <span dir="ltr"><<a href="mailto:bitcoin-dev@lists.linuxfoundation.org" target="_blank">bitcoin-dev@lists.linuxfoundation.org</a>></span> wrote:<br /><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div><div>So I've created 2 new repositories with changed rules regarding sequencenumbers:<br /><br /><a href="https://github.com/maaku/bitcoin/tree/sequencenumbers2" target="_blank">https://github.com/maaku/bitcoin/tree/sequencenumbers2</a><br /><br /></div>This repository inverts (un-inverts?) the sequence number. nSequence=1 means 1 block relative lock-height. nSequence=LOCKTIME_THRESHOLD means 1 second relative lock-height. nSequence>=0x80000000 (most
significant bit set) is not interpreted as a relative lock-time.<br /><br /><a href="https://github.com/maaku/bitcoin/tree/sequencenumbers3" target="_blank">https://github.com/maaku/bitcoin/tree/sequencenumbers3</a><br /><br /></div>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).<br /></div><div class="HOEnZb"><div class="h5"><div class="gmail_extra"><br /><div class="gmail_quote">On Tue, Aug 25, 2015 at 3:08 PM, Mark Friedenbach <span dir="ltr"><<a href="mailto:mark@friedenbach.org" target="_blank">mark@friedenbach.org</a>></span> wrote:<br /><blockq
uote
class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div><div>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.<br /><br /></div><div> * 1 bit is necessary to enable/disable relative lock-time.<br /></div><div><br /></div><div> * 1 bit is necessary to indicate whether seconds vs blocks as the unit of measurement.<br /><br /></div><div> * 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> * 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 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 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 would feel uncomfortable going less than a year for a hard maximum, and am having 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 relative lock-time?<br /></div><div><br /></div>TL;DR <br /></div><div><div><div class="gmail_extra"><br /><div class="gmail_quote">On Sun, Aug 23, 2015 at 7:37 PM, Mark Friedenbach <span dir="ltr"><<a href="mailto:mark@friedenbach.org" target="_blank">mark@friedenbach.org</a>></span> wrote:<br /><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-lef
t:1px
#ccc solid;padding-left:1ex"><p dir="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 ideas?) and then see how many bits you have left over.</p><div><div>
<div class="gmail_quote">On Aug 23, 2015 7:23 PM, "Jorge Timón" <<a href="mailto:bitcoin-dev@lists.linuxfoundation.org" target="_blank">bitcoin-dev@lists.linuxfoundation.org</a>> wrote:<br type="attribution" /><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">On Mon, Aug 24, 2015 at 3:01 AM, Gregory Maxwell via bitcoin-dev<br />
<<a href="mailto:bitcoin-dev@lists.linuxfoundation.org" target="_blank">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? 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 />
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</blockquote></div>
</div></div></blockquote></div><br /></div>
</div></div></blockquote></div><br /></div>
</div></div><br />_______________________________________________<br />
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<br /></blockquote></div><br /></div>
<p style="margin-top: 2.5em; margin-bottom: 1em; border-bottom: 1px solid #000"></p><pre class="k9mail"><hr /><br />bitcoin-dev mailing list<br />bitcoin-dev@lists.linuxfoundation.org<br /><a href="https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev">https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev</a><br /></pre></blockquote></div><br>
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