The use of public key cryptography as described (I mentioned it at my previous post) so far has a number of problems associated with it. These can be solved by incorporating the improvements described below.
One problem is that when Alice and Bob (and all other members of the community) are sending their public keys to the public directory, someone with criminal aspirations (say, Charlie) might intercept the public key and substitute one of his own, keeping the real one to one side. When Bob wants to send a secret message to Alice he gets her public key from the directory, but actually he gets the bogus key from Charlie. Using this key he puts his secret message into a digital envelope and sends it to Alice. (more…)
