Re: e-postage still doesn't work, why IPv6 isn't ready for prime time, SMTP edition

["John R. Levine" <johnl () iecc com>]

> " Contrary to the commonly held belief that this is fundamentally
> impossible, we propose several solutions that do achieve a reasonable level
> of double spending prevention"

Yes, that's Bitcoin's claim to fame.

> Perhaps the number of zeroes doesn't make a difference; but solving the 
> double spending problem would seem to play a much bigger role in making 
> a difference to your conclusion from ten years ago.  Note that one of 
> the concepts around the double spending problem is that of offline 
> spending being able to happen in massively large scale in very short 
> time before the network is rejoined; however, in the case of email, that 
> situation is largely a dead end; if you're not online, you're not going 
> to be making very many mail connections.

If you actually care about this, you might consider what would happen to 
the Bitcoin blockchain if it were attacked with millions of double 
spending transactions.  This paper claims it can't prevent double 
spending, only prevent overspending by a factor of 100, which may be of 
theoretical interest but isn't of much practical use.  We already know how 
to do approximate bulk counting.  Oh, and on the last page, they think 
that hashcash works, to limit transaction rates.

Anyway, if you reread my paper from a decade ago, the bank problem is only 
one of many problems with e-postage, each of which is fatal.

R's,
John