Patent ID: 8001054

Claim:
A method for generating an unpredictable number to facilitate securing a transaction: obtaining, by an Radio Frequency Identification (RFID) reader, variable data; performing, by said RFID reader, a secure hashing algorithm on said variable data to produce a message digest, wherein the secure hashing algorithm is configured to produce a digest of at least 16 bytes; selecting, by said RFID reader, at least one of a left-most 16 bytes or a right-most 16 bytes of said message digest to form a random 16-byte value; creating, by said RFID reader, said unpredictable number using said random 16-byte value as an input for a seeded pseudo-random number generator; determining, by said RFID reader and based upon at least one of an account issuer or a merchant system, a proposed maximum value for said unpredictable number; truncating, by said RFID reader, said unpredictable number, wherein the result of said truncating is said unpredictable number limited to said proposed maximum value; sending, by said RFID reader, the truncated unpredictable number to an RFID transaction device; receiving, by said RFID reader, a cryptogram from said RFID transaction device, wherein said cryptogram includes the truncated unpredictable number; and sending, by said RFID reader, the truncated unpredictable number and said cryptogram to an account issuer, wherein said account issuer validates said cryptogram and verifies that said cryptogram includes the truncated unpredictable number.