Wednesday, April 29, 2009

“One Way Hash” Arguments

Julian Sanchez has made an excellent post on Climate Change argument fallacies where he coins the term “one way hash” arguments. The context of the post is a discussion about the difficulties of refuting false arguments concerning the state of climate change (the politically correct term for global warming), in particular, the difficulties of lay people to understand the arguments of specialists.

Sometimes 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 … 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.

from which he concludes that

… 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 aficionados 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. … 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.”

I found a link to Sanchez’s analysis in a post by Eric Rescorla, who was correcting Sanchez, somewhat pedantically, on the point that hash functions aren’t based on factoring. Sanchez defended himself by stating that he was constructing a metaphor not giving a cryptography lesson.

In any case, crypto nitpicks aside, I like the metaphor, as did others in the comments to Sanchez’s post. I think “one way hash” argument might be a bit wordy, and I would prefer simply a “hashed” argument (but this could be a botched argument), or a even a “product” argument (referring to factoring).

When Sanchez says above that arguments can often reduce to “snappy, intuitively appealing argument without obvious problems” vs. “rebuttal I probably don’t have time to read, let alone analyze closely”, I am reminded of some recent remarks from Marcus Ranum, The Anatomy of Security Disasters, where he observes that

Since we’re not working in a field where the probabilities are simple, like they are on a roulette wheel, we’ve had to resort to making guesses, and trying to answer unanswerable questions … I don’t know a single senior security practitioner who has not, at some point or other, had to defend an estimated likelihood of a bad thing happening against an estimated business benefit.

Often business has the “snappy intuitively appealing arguments without obvious problems” - plus Excel - while if the security practitioner objects, then by contrast, the “rebuttal may require explaining a whole series of preliminary concepts before it’s really possible to explain why the talking point (i.e. business case) is wrong”. Snappy and plausible usually wins out over lengthy, detailed and correct. There is asymmetry at work here, a “one way hash” argument, and security people have ended up with the hard inversion problem.

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2 comments:

pastasid said...

A snappy response:
"plus Excel" - that is what Taleb also mentioned in his book "The Black Swan" - it is such a dangerous tool when applied to make a point - especially about predicting future events (and possible profits - or as is today more popular: losses).

boy labyog said...

Why you don't try mens trousers for your outlook?