Format-preserving encryption algorithms using families of tweakable blockciphers

Abstract

We present two new algorithms, FEA-1 and FEA-2, for secure and efficient format-preserving encryption. Each algorithm is built from a family of dedicated tweakable blockciphers supporting various block bit-lengths. The tweakable blockciphers in the same family have similar structures and are based on common building blocks, enabling security analyses in the same frameworks. Their security follows largely from the structures, the round functions, and the tweak schedules. Their structures are new tweakable Feistel schemes, which are shown to be indistinguishable from tweakable random permutations against adaptive chosen tweak, plaintext, and ciphertext attacks. Their building blocks are shown to have cryptographically strong properties. The proposed algorithms outperform existing ones. They are several times faster than FF1-AES on test platforms.