Here is a method to render Man in the Middle audible on a telephone connection. Before speech can be encrypted, it is digitized and compressed. It is turned into digital packets. There is some choice in the size and other properties of the digital packets. Suppose that Bob's computer from time to time formulates a plan to do groups of a particular size and form, and sends Ann's computer a hash of that plan and the DH negotiated shared secret. Malloc (the man in the middle) cannot send this hash to Ann's computer for Ann would discover the shared secret she is using is not the same as the shared Bob is using. So his computer must formulate its own plan, and send its own hash, which will not agree with Bob's plan, because Bob's computer does not reveal the plan except by actually sending the packets. So malloc must decompress Bob's speech packets, repacketize them, and recompress them, Often he will not be able to send off a packet, until he has received two of Bob's packets. So this triples the delay, and increases the speech degradation. This should quite noticeable, noticeable enough to provoke Bob and Ann into verifying their connection by reading the hash digits of their shared secret. --------------------------------------------------------------------- | We have the right to defend ourselves | http://www.jim.com/jamesd/ and our property, because of the kind | of animals that we are. True law | James A. Donald derives from this right, not from the | arbitrary power of the state. | jamesd@echeque.com