Multiple Encryption with Minimum Key

In this paper we consider multiple encryption schemes built from conventional cryptosystems such as DES. The existing schemes are either vulnerable to variants of meet in the middle attacks, i.e. they do not provide security of the full key or there is no proof that the schemes are as secure as the underlying cipher. We propose a new variant of two-key triple encryption which is not vulnerable to the meet in the middle attack and which uses a minimum amount of key. We can prove a connection between the security of our system and the security of the underlying block cipher.