1 January 2003

Date: Wed, 1 Jan 2003 14:42:03 +0100 (CET)
From: Eugen Leitl <eugen@leitl.org>
To: <cypherpunks@lne.com>
Subject: Re: biological systems and cryptography 

On Wed, 1 Jan 2003 you wrote:

> What's the latest news on Adelman's cryptological
> soup? Once his DNA crypto was touted as a 
> substantial breakthrough for crypto, though since
> overshadowed by quantum crypto smoke-blowing.

DNA computes very slowly; it's bound by viscous drag and brownian noise to
sample nucleotide pair matching. Dry NEMS operates roughly in 100 GHz
regime, tops (complex devices would typically run at 10-100 MHz).  
Electronical components already operate in multiple THz range, I presume
the ceiling for suitable molecular scale components suitably cooled and/or
running in ballistic or even superconducting regime, using mostly
reversible logic (the ratio of ones to zeroes of adjacent bits never
changes much during each step) lies somewhat higher, though it is
difficult to predict how high.

So they are faster than current computers, but the real power comes
because you count your individual computer components in moles. That's the
big jump, as seen from our current capabilities. Once you're there you can
only scale up by making more moles of computronium (a molecular crystal
with units being individual computers). You can make lots of moles from
free floating junk in space by automatic autoamplifying fabbing, but
clearly other people would want to use that resource for themselves, at
least on the long run. But a few cubic miles looks rather doable.

Given a circumsolar cloud of hardware a few lightminutes across (you need
about the mass of Mercury to completely intercept the entire solar output
in a relatively low, uncomfortably hot orbit) you can do a lot of brute
forcing, but it's still finite. The interesting part is when you can make
your molecular stuff act as qubits at high rates of entanglement. QM is
much overhyped, so it's dubious one can make handheld devices equivalent
to above circumsolar machine.

I expect first hybrid 2d molecular memories in about a decade, 3d
integrated stuff will take another decade, or so. That's all without 
invoking machine-phase autoassembly, just synthetic chemistry/biology.