FAST: Secure and High Performance Format-Preserving Encryption and Tokenization

We propose a new construction for format-preserving encryption. Our design provides the flexibility for use in format-preserving encryption (FPE) and for static table-driven tokenization. Our algorithm is a substitution-permutation network based on random Sboxes. Using pseudorandom generators and pseudorandom functions, we prove a strong adaptive security based on the super-pseudorandom permutation assumption of our core design. We obtain empirical parameters to reach this assumption. We suggest parameters for quantum security. Our design accommodates very small domains, with a radix a from 4 to the Unicode alphabet size and a block length ℓ starting 2. The number of Sbox evaluations per encryption is asymptotically ℓ32, which is also the number of bytes we need to generate using 𝖠𝖤𝖲 in 𝖢𝖳𝖱 mode for each tweak setup. For instance, we tokenize 10 decimal digits using 29 (parallel) 𝖠𝖤𝖲 computations to be done only once, when the tweak changes.