Patent ID: 7177848

Claim:
A computerized method of conducting an electronic transaction over a public communications network, with a payment account number having a certain amount of available funds, using a payment network linked to a check site, comprising: (a) computer generating a secret key associated with said payment account number; (b) using said secret key to computer generate a message authentication code specific to said transaction; (c) computer generating an authorization request message including said message authentication code; (d) forwarding said authorization request message over said payment network to said check site for computer verification of the authenticity of said message authentication code; (e) verifying the message authentication code by said check site using said secret key; and (f) responding by computer to said authorization request message over said payment network based on said available funds and said transaction amount, wherein said authorization request message is routed over said payment network based on a special bank identification number corresponding to said check site, wherein said authorization request message includes an expiration date field and said message authentication code is placed in said expiration date field, wherein said payment account number is issued by an issuer and said response is provided by said issuer; and further comprising, providing software at a user location for generating said secret key.