Block Cipher Modes of Operation for Heterogeneous Format Preserving Encryption

Format-preserving encryption (FPE), a kind of symmetric encryption, has caught a great deal of attention of late years. FPE, as the name suggests, does not change the format of inputs which may include the length of inputs, coding of characters or data size of inputs. It is very useful to encrypt or generate some data with fixed format such as credit card numbers (CCN), social security numbers (SSN) or even address. With this encryption, we can add encryption to existing applications without changing structures including input-output format or decreasing those performance. In this work we develop and discuss block cipher modes of operation for FPE which are applicable for messages consisting of multibyte characters and their securities. This paper also gives a way to implement these modes for the format consisting of characters encoded by EUC or UTF-8 and its performance. Formats consisting of multibyte characters - we call those "heterogeneous formats" - are very important in many countries including Japan where "Kanji" or other multibyte characters are used. In addition, this paper gives an efficient way to encrypt messages of such formats and modes of operations to realize a high performance encryption algorithm.