Patent ID: 7024395

Claim:
A method for securing a transaction in order to prevent fraudulent transactions, said method comprising: receiving prior to the transaction a secret master key from a third party, wherein the master key remains unchanged and is kept secret, and is not altered after the transaction, the third party storing a copy of the master key; receiving a request for a digest from a requestor; retrieving the master key; retrieving unique client information; the client information being associated with the master key; creating the digest by hashing the unique client information and the master key; returning the digest and the unique client information to the requester, wherein the digest and the unique client information will be used for transacting with the third party; wherein the request further comprises unique requester information and creating the digest further comprises hashing the unique requester information; and wherein the transaction is a credit card transaction, the third party is a credit card issuer and the requestor is a merchant, further wherein the unique requester information includes information describing a merchant identifier which is specific to the credit card issuer, a transaction identifier which is specific to the credit card issuer and purchase information which is specific to a purchase initiated by the client.