An efficient session key generation protocol

Key exchange is an important subject in the cryptosystem, which has marched the world into the complicated application of communication technology nowadays. A common cryptographic technique is used to encrypt each individual´s conversation with a separate key, which is the so-called session key. The lifespan of a session is the period of a particular communication session. Instead of depending on a discrete logarithm like many previously proposed schemes, we use public key cryptography here. In this paper, we would combine key exchange with a digital signature. Adopting the ring topology and the co-operating with the RSA algorithm to encrypt secret random numbers, every one gets all the random numbers after several turns, and then the session key is generated. Because of the presence of a trusted third party, our proposed protocol can withstand the man-in-the-middle attack as well.