2-KEY TRIPLE ENCRYPTION

In this paper we consider multiple encryption schemes built from conve ntional cryptosystems such as DES. The existing schemes are either vul nerable to variants of meet-in-the-middle attacks, i.e., they do not p rovide security corresponding to the full key length used or there is no proof that the schemes are as secure as the underlying cipher. We p ropose a variant of two-key triple encryption with a new method of gen erating three keys from two. Our scheme is not vulnerable to the meet- in-the-middle attack and, under an appropriate assumption, we can show that our scheme is at least about as hard to break as the underlying block cipher.