A method for conducting an electronic transaction, the method comprising: initiating an electronic transaction between a mobile device and a point of sale reader device; applying a consumer personal device identifier that identifies the mobile device and shared secret data as inputs to a cryptographic function in the mobile device, such that the consumer personal device identifier is encrypted by the cryptographic function, and wherein the shared secret data is a key or password shared by both the mobile device and an issuer server and is established by an application in the mobile device with the issuer server via a cellular network or Internet network upon an initial use of the application and is used as a means to encrypt the output of the cryptographic function; inserting the output of the cryptographic function that includes the encrypted consumer personal device identifier into legacy transaction formatted data, wherein the legacy transaction formatted data further includes an unencrypted user identifier associated with a user of the mobile device and an unencrypted bank identification number; wirelessly providing the legacy transaction formatted data from the mobile device to the POS reader device via the electronic transaction; forwarding, from the POS reader device, the legacy transaction formatted data to the issuer server, wherein the issuer server is identified by the unencrypted BIN; processing, at the issuer server, the legacy transaction formatted data to verify the user and request authorization for the electronic transaction, wherein processing the legacy transaction formatted data includes, by the issuer server, using the unencrypted user identifier to access a shared secret database in the issuer server to obtain a local copy of the shared secret data, decrypting the encrypted consumer personal device identifier included in the legacy transaction formatted data using the local copy of the shared secret data, comparing the decrypted consumer personal device identifier with a stored personal device identifier in the issuer server, which was automatically provided to the issuer server by the application upon the initial use of the application, to verify the user, validating card credentials stored at an account server in the event the user is verified, and utilizing the stored card credentials to authorize the electronic transaction; sending, to the POS reader device, a notification message that indicates that the electronic transaction is authorized; and conducting, at the POS reader device, the electronic transaction upon receipt of the notification message. initiating an electronic transaction between a mobile device and a point of sale reader device; applying a consumer personal device identifier that identifies the mobile device and shared secret data as inputs to a cryptographic function in the mobile device, such that the consumer personal device identifier is encrypted by the cryptographic function, and wherein the shared secret data is a key or password shared by both the mobile device and an issuer server and is established by an application in the mobile device with the issuer server via a cellular network or Internet network upon an initial use of the application and is used as a means to encrypt the output of the cryptographic function; inserting the output of the cryptographic function that includes the encrypted consumer personal device identifier into legacy transaction formatted data, wherein the legacy transaction formatted data further includes an unencrypted user identifier associated with a user of the mobile device and an unencrypted bank identification number; wirelessly providing the legacy transaction formatted data from the mobile device to the POS reader device via the electronic transaction; forwarding, from the POS reader device, the legacy transaction formatted data to the issuer server, wherein the issuer server is identified by the unencrypted BIN; processing, at the issuer server, the legacy transaction formatted data to verify the user and request authorization for the electronic transaction, wherein processing the legacy transaction formatted data includes, by the issuer server, using the unencrypted user identifier to access a shared secret database in the issuer server to obtain a local copy of the shared secret data, decrypting the encrypted consumer personal device identifier included in the legacy transaction formatted data using the local copy of the shared secret data, comparing the decrypted consumer personal device identifier with a stored personal device identifier in the issuer server, which was automatically provided to the issuer server by the application upon the initial use of the application, to verify the user, validating card credentials stored at an account server in the event the user is verified, and utilizing the stored card credentials to authorize the electronic transaction; sending, to the POS reader device, a notification message that indicates that the electronic transaction is authorized; and conducting, at the POS reader device, the electronic transaction upon receipt of the notification message.