Proof of Work -> atmospheric carbon

[Nicolas Williams]

On Wed, Jan 28, 2009 at 04:35:50PM -0500, Jerry Leichter wrote:
> [Proposals to use reversible computation, which in principle consume  
> no energy, elided.]
> 
> There's a contradiction here between the computer science and economic
> parts of the problem being discussed.  What gives a digital coin value
> is exactly that there is some real-world expense in creating it.

For some definition of "digital coin."

An alternative design where all coins are double-spend checked against
on-line infrastructure belonging to the issuer don't have this
constraint.  Though they have different properties.  For example,
anonymity might then depend on trusting mixmaster-type networks to
exchange coins the issuer knows you have for coins that the issuer
doesn't know you have, but that might make anonymity entirely
impractical.  But then, how practical are POW coins anyways?

I suspect most people in the formal sectors of most economies would
gladly live with digital credit/bank cards most of the time and to heck
with digital coins.

> So, how do you tie the cost of a token to power?  Curiously, something  
> of the sort has already been proposed.  It's been pointed out - I'm  
> afraid I don't have the reference - that CPU's keep getting faster and  
> more parallel and a high rate, but memories, while they are getting  
> enormously bigger, aren't getting much faster.  So what the paper I  
> read proposed is hash functions that are expensive, not in CPU  
> seconds, but in memory reads and writes.  Memory writes are inherently  
> non-reversible so inherently cost power; a high-memory-write algorithm  
> is also one that uses power.

Clever!

Nico
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