Julian Sanchez's

post about the difficulty
of evaluating technical arguments has been circulating
fairly widely. In the
middle is a somewhat strained analogy to cryptography:

Sometimes, of course, the arguments are such that the specialists can
develop and summarize them to the point that an intelligent layman can
evaluate them. But often--and I feel pretty sure here--that's just not
the case. Give me a topic I know fairly intimately, and I can often
make a convincing case for absolute horseshit. Convincing, at any
rate, to an ordinary educated person with only passing acquaintance
with the topic. A specialist would surely see through it, but in an
argument between us, the lay observer wouldn't necessarily be able to
tell which of us really had the better case on the basis of the
arguments alone--at least not without putting in the time to become
something of a specialist himself. Actually, I have a possible
advantage here as a peddler of horseshit: I need only worry about what
sounds plausible. If my opponent is trying to explain what's true, he
may be constrained to introduce concepts that take a while to explain
and are hard to follow, trying the patience (and perhaps wounding the
ego) of the audience.
Come to think of it, there's a certain class of rhetoric I'm going to
call the "one way hash" argument. Most modern cryptographic systems in
wide use are based on a certain mathematical asymmetry: You can
multiply a couple of large prime numbers much (much, much, much, much)
more quickly than you can factor the product back into primes. A
one-way hash is a kind of "fingerprint" for messages based on the same
mathematical idea: It's really easy to run the algorithm in one
direction, but much harder and more time consuming to undo. Certain
bad arguments work the same way--skim online debates between biologists
and earnest ID afficionados armed with talking points if you want a
few examples: The talking point on one side is just complex enough
that it's both intelligible--even somewhat intuitive--to the layman and
sounds as though it might qualify as some kind of insight. (If it
seems too obvious, perhaps paradoxically, we'll tend to assume
everyone on the other side thought of it themselves and had some good
reason to reject it.) The rebuttal, by contrast, may require
explaining a whole series of preliminary concepts before it's really
possible to explain why the talking point is wrong. So the setup is
"snappy, intuitively appealing argument without obvious problems"
vs. "rebuttal I probably don't have time to read, let alone analyze
closely."

Unfortunately, Sanchez has the cryptography pretty much wrong.
He's confused two totally separate
cryptographic concepts: public key cryptography, and one-way
hashes. Some PKC (but not all) involves multiplying large
prime numbers. Hash functions (with the exception of VSH,
which is impractically slow and not in wide use), don't
involve prime numbers at all. Neither does symmetric
encryption, which is what you actually use to encrypt data
(PKC is used primarily for key exchange and authentication/signature). Now, it's
true that prime multiplication is indeed a one-way function
(or at least we hope it is) and hash functions are
intended to be as well, but other than that, there's not
much of a connection.^{1}
That said, however, I've seen this post referenced
several places, and with the exception of Paul Hoffman,
who pointed it out to me, few seem to have noticed, that,
well, it's horseshit. I suppose this is an argument in
favor of Sanchez's thesis.

^{1.}Hash functions are actually one-way in
an important sense that prime number multiplication is not:
any given integer only has one unique factorization, whereas
there are many messages that hash to a single value,
so it's always possible with enough computational effort
to reconstruct the original primes. However, given
a hash value and no other information, it's not possible
to determine which of the possible input messages was
fed in.