[bitcoin-dev] Fill-or-kill transaction

[jl2012 at xbt.hk]

Peter Todd via bitcoin-dev 於 2015-09-17 18:44 寫到:

> It can be implemented by a "treat like Coinbase" flag in the
> UTXO set, set when the output is created.

I think this is the cleanest way to implement the maturity requirement. 
I understand why we need maturity, However, requiring 100 block maturity 
will unfortunately make the system much less appealing since the 
recipient may not like it. A fill-or-kill tx may still be used as the 
initial funding tx to the Lightning Network, as long as the counterparty 
is willing to take the extra risk.

Actually, a fill-or-kill tx is slight safer than a coinbase tx, 
depending on the difference between the absolute kill time and actual 
confirmation time. In a re-org, an orphaned coinbase tx is permanently 
invalidated and has no hope to be included again. However, an orphaned 
fill-or-kill tx may still be confirmed by another miner. If there is 
still a few days until the absolute kill time, a fill-or-kill tx is 
basically as safe as a normal tx.

With possibility of re-org and unpredictable block interval in mind, 
height-based fill-or-kill is not very useful since it is difficult for 
users to determine the actual kill time. If we could abolish the idea of 
height-based fill-or-kill, the resolution of time-based fill-or-kill 
might be improved.


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Chun Wang 於 2015-09-17 18:33 寫到:
> We are currently using nLockTime for share info and nSequence for
> extranonce2. I have carefully reviewed the reference implementation of
> BIP68 and it should be compatible, but this proposal may break the
> implementation unless it does not affect coinbase transactions.
> 

The fill-or-kill system is totally optional, using a bit flag in tx 
nVersion to indicate. Everything should be fine unless you are also 
messing with the nVersion


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Btc Drak 於 2015-09-17 15:12 寫到:
> Forgive me if I have missed the exact use-case, but this seems overly
> complex. Surely fill-or-kill refers to getting a transaction confirmed
> within a few confirms or to drop the tx from the mempool so it wont be
> considered for inclusion anymore. As such, you could just repurpose a
> small range of nLocktime such that a TX will be accepted into mempool
> for a specific period before expiring.

What I'm describing is to implement fill-or-kill as consensus rule. 
Certainly, we could implement it at the P2P network level: everything is 
the same as I described, but the nLockTime2 and nKillTime are for 
reference only and tx validity depends only on the nLockTime. Benevolent 
miners should drop the tx after the suggested kill time but there is no 
guarantee


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I made a mistake in this example:

> A user wants his tx get confirmed in the block 630000, the first block
> with reward below 10BTC. He is willing to pay high fee but don't want
> it gets into another block. He will set nLockTime2 = 210,000 and
> nKillTime = 0

The correct nLockTime2 for this example should be 210000/4 = 52500