[137335] in cryptography@c2.net mail archive
Re: Bitcoin P2P e-cash paper
daemon@ATHENA.MIT.EDU (Satoshi Nakamoto)
Tue Nov 11 09:30:13 2008
Date: Tue, 11 Nov 2008 06:18:20 +0800
From: "Satoshi Nakamoto" <satoshi@vistomail.com>
Reply-To: satoshi@vistomail.com
To: jamesd@echeque.com
Cc: cryptography@metzdowd.com
James A. Donald wrote:
> So what happened to the coin that lost the race?
>
> ... it is a bit harsh if the guy who came second=20
> is likely to lose his coin.
When there are multiple double-spent versions of the same transaction, o=
ne and only one will become valid.
The receiver of a payment must wait an hour or so before believing that =
it's valid. The network will resolve any possible double-spend races by=
then.
The guy who received the double-spend that became invalid never thought =
he had it in the first place. His software would have shown the transac=
tion go from "unconfirmed" to "invalid". If necessary, the UI can be ma=
de to hide transactions until they're sufficiently deep in the block cha=
in.
> Further, your description of events implies restrictions
> on timing and coin generation - that the entire network
> generates coins slowly compared to the time required for
> news of a new coin to flood the network
Sorry if I didn't make that clear. The target time between blocks will =
probably be 10 minutes.
Every block includes its creation time. If the time is off by more than=
36 hours, other nodes won't work on it. If the timespan over the last =
6*24*30 blocks is less than 15 days, blocks are being generated too fast=
and the proof-of-work difficulty doubles. Everyone does the same calcu=
lation with the same chain data, so they all get the same result at the =
same link in the chain.
> We want spenders to have certainty that their
> transaction is valid at the time it takes a spend to
> flood the network, not at the time it takes for branch
> races to be resolved.
Instantant non-repudiability is not a feature, but it's still much faste=
r than existing systems. Paper cheques can bounce up to a week or two l=
ater. Credit card transactions can be contested up to 60 to 180 days la=
ter. Bitcoin transactions can be sufficiently irreversible in an hour o=
r two.
> If one node is ignoring all spends that it does not=20
> care about, it suffers no adverse consequences.
With the transaction fee based incentive system I recently posted, nodes=
would have an incentive to include all the paying transactions they rec=
eive.
Satoshi Nakamoto
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