Regarding the secure messaging feature, be aware of:
Signcryption
Digital Signcryption or How to Achieve
Cost(Signature & Encryption) <<
Cost(Signature) + Cost(Encryption)
Claims to eliminate the need to sign and encrypt in separate steps as PGP does. I didn't read it yet, just passing it along.
Signcryption, a kind of public key cryptosystem,
succeeds in simultaneously encrypting the message
while digitally signing. Compared with the traditional
systems like PGP that executes signing and encrypting
a message in sequential procedures, such a
characteristic makes signcryption system securer and
more efficient. To be specific, the efficiency of
performance based on the signcryption system can be
enhanced atout 50% to 90% than the traditional ones