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As far as I can see, no matter how the session keys are generated (be it
Diffie-Hellman or whatever), any Cripple conversation which travels in
whole or in part over a land-line is vulnerable to this scheme.  Law-
enforcement agencies can do it legally at the telco, or illegally by finding
some part of the phone line that they can cut into.  The degree of risk
depends very much on location - not good in the middle of a busy street,
but not bad on a line in open country (leading to a drug lord's ranch).  The
only way to defeat it would be if your phone had the equivalent of a public
key indexed against phone number for every phone you might want to call (all
of them) - totally impractical, even if some part of the Cripple algorithm
could be used as a kind of public key (I don't understand enough about these
things to know).

This sort of encryption scheme is only really workable over a radio link,
and even then you could probably interevene without causing problems for
other phones nearby if you were physically close to the target phone.

Gosh, yet another way to get round Cripple encryption.  How many is that
we've found so far?  And that's without even knowing the details of the
algorithm.

- --Paul

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