alice and bob use the Hellman-diffie protocol to exchange keys and identify each other with certificates, signed by a trusted certifier (CA) and each has a private key that matches the public seducer in his certificate. eve tries to carry out a Middle-in-Men attack on alice and bob. eve can intervene at every stage in the communication between alice and bob. alice certificate will be- CERT1, and bob certificate will be- CERT2. alice signature on message m will be- SIG1(m), and bob signature on message m will be- SIG2(m). alice and bob begin the protocol by exchanging DH key and at the end hold a common key k. show if eve can succeed when the protocol continues as a follows:
- alice choose r1 randomaly and sends to bob < r1, CERT1 > and bob randomaly choose r2 and sends to alice < r2, CERT2 >
- alice and bob verify each others certificate, if the confirmations is successful alice sends SIG1(k xor r2) to bob that returns to her SIG2(k xor r1)
- if both signatures are correct then alice and bob encrypt the traffic between them using k.
