Introduction to Cryptography with Coding Theory, 3rd Edition

15.2 Key Distribution

So far in this book we have discussed various cryptographic concepts and focused on developing algorithms for secure communication. But a cryptographic algorithm is only as strong as the security of its keys. If Alice were to announce to the whole world her key before starting an AES session with Bob, then anyone could eavesdrop. Such a scenario is absurd, of course. But it represents an extreme version of a very important issue: If Alice and Bob are unable to meet in order to exchange their keys, can they still decide on a key without compromising future communication?

In particular, there is the fundamental problem of sharing secret information for the establishment of keys for symmetric cryptography. By symmetric cryptography, ...