Method, apparatus, and computer-readable medium for format preserving encryption of a numerical value

Abstract

A system, method and computer-readable medium format-preserving encryption of a numerical value, including storing a binary numerical value, the binary numerical value comprising a plurality of binary bits, dividing the plurality of binary bits into a plurality of bit groups and storing the plurality of bit groups in a plurality of bytes, encrypting each byte in the plurality of bytes using a radix value corresponding to a quantity of binary bits in a bit group corresponding to that byte to generate a plurality of ciphertext bytes, and combining a quantity of least-significant bits from each ciphertext byte in the plurality of ciphertext bytes to generate a binary ciphertext value, the quantity of least-significant bits combined from each ciphertext byte corresponding to the radix value used to generate that ciphertext byte.

We claim: 
     
         1 . A method executed by one or more computing devices for format-preserving encryption of a numerical value, the method comprising:
 storing a binary numerical value, the binary numerical value comprising a plurality of binary bits;   dividing the plurality of binary bits into a plurality of bit groups and storing the plurality of bit groups in a plurality of bytes;   encrypting each byte in the plurality of bytes using a radix value corresponding to a quantity of binary bits in a bit group corresponding to that byte to generate a plurality of ciphertext bytes; and   combining a quantity of least-significant bits from each ciphertext byte in the plurality of ciphertext bytes to generate a binary ciphertext value, wherein the quantity of least-significant bits combined from each ciphertext byte corresponds to the radix value used to generate that ciphertext byte.