2047 bit keys in PGP

[Mark Grant, M.A. (Oxon)]

On 4 Jan 1996, Ian Goldberg wrote:

> in a brute-force search.  From Applied Crypto, 2nd ed, pp157-158,
> setting or clearing one bit takes at _least_ 4.4*10^-16 erg of energy.

I thought reversible computing could use an arbitarily small amount of 
energy in computations ? Or is it that you can use it to get down to this 
level of energy loss, but not below ? I'm not sure.

	Mark