1. A method of generating a format-preserving token for sensitive data, said method comprising the computer-implemented steps of: receiving from a client process an input data string corresponding to sensitive data; generating a tokenized data string according to a token generation algorithm that includes a Luhn validation routine and a string length determiner, wherein the data values of the characters in said tokenized data string are independent of the data values of at least a portion of the characters in said input data string; and returning said tokenized data string to said client process in response to a request.