Unconditional Security in Cryptography
Lectures on Data Security, Modern Cryptology in Theory and Practice, Summer School, Aarhus, Denmark, July 1998
Elements of Information Theory (Wiley Series in Telecommunications and Signal Processing)
Elements of Information Theory (Wiley Series in Telecommunications and Signal Processing)
One-way functions are essential for complexity based cryptography
SFCS '89 Proceedings of the 30th Annual Symposium on Foundations of Computer Science
| Hi-index | 0.00 |
In this note we revisit the famous result of Shannon [Sha49] stating that any encryption scheme with perfect security against computationally unbounded attackers must have a secret key as long as the message. This result motivated the introduction of modern encryption schemes, which are secure only against a computationally bounded attacker, and allow some small (negligible) advantage to such an attacker. It is a well known folklore that both such relaxations -- limiting the power of the attacker and allowing for some small advantage -- are necessary to overcome Shannon's result. To our surprise, we could not find a clean and well documented proof of this folklore belief. (In fact, two proofs are required, each showing that only one of the two relaxations above is not sufficient.) Most proofs we saw either made some limiting assumptions (e.g., encryption is deterministic), or proved a much more complicated statement (e.g., beating Shannon's bound implies the existence of one-way functions [IL89].)