SECURITY EXERCICES PART II
Question #1
Alice wants to send a cellphone text message to Bob securely, over an insecure communication
network. Alice's cellphone has a RSA public key KA and matching private key vA; likewise, Bob's
cellphone has KB and vB.
Let's design a cryptographic protocol for doing this, assuming both know each other's public
keys. Here is what Alice's cellphone will do to send the text message m:
Alice's phone randomly picks a new AES session key k and computes the following:
c = RSA Encrypt (KB; k),
c’= AES-CBC-Encrypt(k;m)
t = RSA-Sign(vA; (c; c’))