US Patent 9070129 Method and system for securing data fields

A merchant conducting a transaction on an account forms transaction data with a sensitive data field. To obscure the account prior to transmitting information about the transaction, for each character in the sensitive data field, a combined character is formed with a character of a generated pad. A replacement character is formed by a modulus operation on the combined character and is stored in the corresponding position in the sensitive data field. A transmission containing the sensitive data field with replacement characters is delivered to the merchant's acquirer.