Cryptology

Cryptology has advanced tremendously since 1976; this chapter provides a brief overview of the current state-of-the-art in the field. Several major themes predominate in the development. One such theme is the careful elaboration of the definition of security for a cryptosystem. A second theme has been the search for provably secure cryptosystems, based on plausible assumptions about the difficulty of specific number-theoretic problems or on the existence of certain kinds of functions (such as one-way functions). A third theme is the invention of many novel and surprising cryptographic capabilities, such as public-key cryptography, digital signatures, secret-sharing, oblivious transfers, and zero-knowledge proofs. These themes have been developed and interwoven so that today theorems of breathtaking generality and power assert the existence of cryptographic techniques capable of solving almost any imaginable cryptographic problem