[Patents] EPO patent on challenge & response authentification

[phm@a2e.de (PILCH Hartmut)]

Under

        http://swpat.ffii.org/vreji/pikta/txt/ep/0427/465/

the EPO awarded ownership of the principle of challenge and response
cryptography to AT&T.

To infringe on the patent, you need to construct a system for
authentification where the key (smartcard) sends a string to
the gate (authentication device) and the latter sends back a testing
number (challenge).  Both key and gate have two secret algorithms
that allow them to produce a response that can then be compared.

The patent also teaches that you can prevent the eavesdropper from
guessing the hidden algorithm by introducing a minimum time interval
between two information exchanges and by using long numbers.

So far I had the impression that crypto patents contain some fairly
non-trivial mathematics and are thus likely to be under-represented
in our horror gallery.  But that impression may be wrong.  At least this
AT&T patent seems to deserve some special honorary place.  Or did I
overlook anything?

-phm



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