Tweakable block ciphers - eScholarship
Moses D. Liskov, Ronald L. Rivest, David A. Wagner · 2002
We propose a new cryptographic primitive, the tweakable block cipher. Such a cipher has not only the usual inputs - message and cryptographic key - but also a third input, the tweak. The tweak serves much the same purpose that an initialization vector does for CBC mode or that a nonce does for OCB mode. Our proposal thus brings this feature down to the primitive block-cipher level, instead of incorporating it only at the higher modes-of-operation levels. We suggest that (1) tweakable block ciphers are easy to design, (2) the extra cost of making a block cipher tweakable is small, and (3) it is easier to design and prove modes of operation based on tweakable block ciphers.