Enhancing the Strength of Conventional Cryptosystems

We look at various ways of enhancing the strength of conventionalcryptosystems such as DES by building a new system which has longerkeys and which uses the original system as a building block. We proposea new variant of two-key triple encryption which is not vulnerableto the meet in the middle attack by van Oorschot and Wiener. Underan appropriate assumption on the security of DES, we can prove thatour system is at least as hard to break as single DES.