 
   Not necessarily.  I've been thinking about this, and if this chip/scheme
is to provide any real security, there must be some sort of key exchange,
either using a public-key encryption scheme, or using a key exchange scheme
like Diffie-Hellman.  If there's an out-of-band transmission of a shared
session key, then what protects that band from eavesdropping?  If the phone
company or some other online central authority generates a session key and
sends it to both users, then what's the point of going to the trouble of
having some complicated key-depositories?  Just ask the phone company for
a copy of the session key for each call.
 
   Now, it's probably not practical for each user to keep an online copy of
every public key used by anyone anywhere, right?  So, probably, there will
be some way of getting these keys verified.  This might be a digitally-
signed (by the chip manufacturer) copy of the public key in this unit,
stored by this unit.  It might also be an online directory with access to
everyone's public keys.  (This would introduce another weakness to the
security of the scheme, of course.)  Presumably, if you don't use your
designated key, you can't get a verified connection to other standard chips.
 
   It might be useful to have a modified chip, which would allow you to
use either the original public/private key pair, or some other key pair
and verification scheme.  Unfortunately, this would not allow you to call
most people and establish secure communications....