An Efficient Format-Preserving Encryption Scheme Based on RECTANGLE

FPE (Format-Preserving Encryption) is a special block cipher that allows message to be encrypted while maintaining its data format within message domain. This enables the secure encryption of not only binary strings but also specific types of data such as email accounts and phone numbers. In this work, we present a novel Feistel-based format-preserving encryption scheme, constructed on the RECTANGLE block cipher, termed RFPE (RECTANGLE-FPE for short). By converting the original plaintext to an unsigned 8-byte format, RFPE has the flexibility to support a large radix, covering daily usage scenarios such as numeric strings and case-insensitive alphabetic characters. Compared with the NIST standardized algorithms FF1 and FF3-1, the implement instance of RFPE outperforms higher throughput across different radix values and data lengths. We describe the equivalent security of RPFE and the RECTANGLE cipher, which can achieve Pseudorandom Permutation security.