You wrote:

You don't always need the correct answer. You just need the correct answer most of the time. You're trying to create a presumption about behavior. Ensuring that you can't read almost all of the traffic is a pretty good way to assure people that you don't try to make sense of any of it.

I'm still not making my point. Encryption is not a data 'state' that can be tested for in the way that liquid/solid/vapour are states of matter. Encryption is a data 'interpretation' for which there are an arbitrairly large number of interpretations available for any given dataset. There is no algorithmic test that can applied to a dataset that will be able to establish the existance or non-existance of a given interpretation. If you're given an unkown dataset and are asked the question, 'Is this an image file' or 'Is this an encrypted file' or 'Is this an audio clip', there is no algorithmic test that can answer any of these questions in either the affermative or the negative. This is just an alternate phrasing of Goedel's Undecidability Theorem. This problem lies permanantly outside the outer boundary of algorithmic capability. Let me now spin a little tale as to how this affects an operator of a re-mailer or datahaven. This tale has two characters, Paco the child pornogropher and Eric the honest RM/DH operater. Paco begins by inventing the new 'Foolproof Barometric Graphic Image Format' (aka FooBar GIF) of which only Paco knows the internals. A FooBar GIF has a statistical profile that looks remarkably like a PGP file, in fact it even comes with a PGP header! Nothing illegal here. Now Paco writes a FooBar GIF Viewer which he sales to child-porn types. Again, there's nothing illegal about the sale of such a piece of software. Paco now anonymously loads Eric's DH with lots of child-porn FooBar GIF's via Eric's anon-RM. These files of course sail right through Eric's filters with nary a scratch. As far as Eric knows he's holding PGP encrypt files. Now Paco advertises the availability of lots of 'good' picture on Eric's DH that can be used with the newly purchased FooBar GIF Viewers. Then the cops get ahold of one of Paco's FooBar GIF Viewers and downloads some FooBar GIFs from Eric's DH and the last words we ever hear from Eric are "I swear I thought they were PGP files, I swear to God I thought they were....." as the authorities drag his carcass off to jail. Whose going to believe Eric's protests of innocence? "After all", says the prosecutor to the jury, "wasn't Eric explicitly filtering out what he didn't want in. If fact", says the prosecutor, "his filter seems to have been designed specifically to allow these kiddie-porn files in and to reject all others." A sad end indeed! Dale H.