Encoding of Korean characters with less radix in format-preserving encryption

In this paper, we suggest how to efficiently convert a Korean character string into an encoded numeral string for format-preserving encryption (FPE). We also present a decoding method that transforms the encoded numeral string into the data string with the original format. When Korean characters as well as English alphabets, numbers, and special characters are used in letters consisting of input of FPE, a radix by using our proposal is just 189 in EUC-KR and 163 in UTF-8, while the existing sequential encoding method requires radix 2,445 and 11,267, respectively. According to our proposal, the plaintext string containing Korean character encrypts the ciphertext string that retains its original length. Likewise, the ciphertext string decrypts the plaintext string with the same length and character type. Moreover, less radix than the existing method offers the better FPE performance.