Format preserving encryption methods for data strings with constraints

摘要

Format preserving encryption (FPE) cryptographic engines are provided for performing encryption and decryption on strings. A plaintext string may be converted to ciphertext by repeated application of a format preserving encryption cryptographic algorithm. Following each application of the format preserving cryptographic algorithm, the resulting version of the string may be analyzed to determine whether desired string constraints have been satisfied. If the string constraints have not been satisfied, further applications of the format preserving cryptographic algorithm may be performed. If the string constraints have been satisfied, the current version of the string may be used as an output for the cryptographic engine.

主权项

1. A method for performing cryptographic operations at computing equipment, comprising:
with the computing equipment, obtaining a plaintext version of a string of characters that have a given format; computing a checksum value string for the plaintext version of the string of characters; and with the computing equipment, repeatedly applying a format preserving encryption algorithm to the string of characters until an encrypted version of the string of characters is produced that complies with the given format and has a checksum value string that matches the checksum value string that was computed for the plaintext version of the string of characters.