Tweakable enciphering schemes using only the encryption function of a block cipher

A new construction of block cipher based tweakable enciphering schemes (TES) is described. The major improvement over existing TESs is that the construction uses only the encryption function of the underlying block cipher. Consequently, this leads to substantial savings in the size of hardware implementation of TES applications such as disk encryption. This improvement is achieved without loss in efficiency of encryption and decryption compared to previously known schemes. We further show that the same idea can also be used with a stream cipher which supports an initialization vector (IV) leading to the first example of a TES from such a primitive.

► New constructions of tweakable enciphering schemes (TESs) are proposed.
► Requires only the encryption module of a block cipher.
► Security under a weak assumption on the underlying block cipher.
► Avoiding the decryption module reduces the size of hardware implementations.
► The first construction of a TES from a stream cipher with an initialization vector.