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Crypto Archives: Re: [honig<img src="/imgs/at.gif" align="middle" border="0">sprynet.com: Re: secure time-stampe

Re: [honigsprynet.com: Re: secure time-stamped envelopes]

Bill Stewart (bill.stewartpobox.com)
Wed, 29 Sep 1999 00:33:51 -0700

At 05:46 PM 09/28/1999 -0500, Jim Choate wrote:
>----- Forwarded message from David Honig <honigsprynet.com> -----
> > So, how many moles of the chemical do you need to do this?
> > How long are the sequences?
>
> > This was the downfall of the briefly interesting DNA search computers
> > (e.g., TSP).

>The DNA sequences themselves can be of infinite length as far as I am aware.
>They are terminated by special ends. The number of base pairs between them
is
>unlimited.
>
>Don't know what TSP is and I've certainly never heard of ANY downfall of DNA
>computers. So far today they've made pretty impressive progress.

The DNA sequences can't be of infinite length unless you've got
infinite quantities of amino acids, a long or infinite time to cook,
an infinite space to cook them in, and a potentially-infinite size or time
to decide if a sequence you get works.

TSP is, of course, the Travelling Salesman Problem, the NP-hard problem
that Adleman used to demonstrate his DNA computer with.
The big problem with DNA computers is that they don't give you a way
to do exponentially many things in polynomial time (unlike
quantum computers, which can (for small exponents) and which
may be able to do for larger exponents). They just speed up the
calculations by a hopefully large constant that's proportional
to the quantity of liquid computer virus you're using.
Solving an exponentially-large problem a million times faster,
is a good start, but that just means the other side needs to add
20 bits to the difficulty of the problem, which isn't many
and doesn't slow them down much.

You can argue about whether this means that DNA computers are meaningful;
they're definitely cool stuff, but don't make any long-term change in
cryptographer-vs-cryptanalyst power struggles - encryption wins.

                                Thanks!
                                        Bill
Bill Stewart, bill.stewartpobox.com
PGP Fingerprint D454 E202 CBC8 40BF 3C85 B884 0ABE 4639

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