In order to make it more difficult to obtain numbers that can be used to conduct fraudulent transactions, a portion of a real account number is encrypted. The encrypted portion of the account number is used to generate a new account number, a new expiration date, and a new verification value. This information can be determined using processor that may reside in a point of sale terminal, a smart card, or a computer operated by a user. The new account number, the new expiration date, and the new verification value can be used in a payment transaction. A server computer in a central payment processing network may determine that the new account information is not the real account information, and may subsequently generate a modified authorization request message using the real account information and may send it to an issuer for approval. The transmission of data is more secure, since real account information is not sent from the merchant to the payment processing network.