[cryptography] Bitcoin observation

dan at geer.org dan at geer.org
Tue Jul 5 07:59:38 EDT 2011

Jon Callas writes:
 | Did you know that if a Bitcoin is destroyed, then the value of all
 | the other Bitcoins goes up slightly? That's incredible. It's amazing
 | and leads to some emergent properties.

I suspect that this is true of gold as well -- send it into
space or bury it in dead people's bridgework and the economic
value of the remaining gold surely rises at least insofar as the
recovery of that lost gold, while possible, would require new
work to do so.

In any case, I just finished reading Glieck's _The Information_
and on page 361-362 of the hardcover edition, there is a passage
discussing how Von Neumann got it wrong when he concluded that
"every elementary act of information processing, every choice
between two alternatives" pays an energy price.  This claim was
refuted by Landauer who showed that "most logical operations
have no entropy cost at all.  When a bit flips from zero to one,
or vice versa, the information is preserved.  The process is
reversible.  Entropy is unchanged, no heat needs to be dissipated.
Only an irreversible operation increases entropy."

Landauer was followed by Bennett who "pursued Landauer's principle
by analyzing every kind of computer he could imagine, real and
abstract, from Turing machines and messenger RNA to 'ballistic'
computers, carrying signals via something like billiard balls.
He confirmed that a great deal of computation can be done with
no energy cost at all.  In every case, Bennett found, heat
dissipation occurs only when information is erased.  Erasure is
the irreversible operation.  When the head on a Turing machine
erases one square of the tape, or when an electronic computer
clears a capacitor, a bit is lost and _then_ heat must be
dissipated.  Forgetting takes work."

I may be mulling this over for some time.


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