1. A method comprising: linking, by a fraud prevention computer, an identifier of a mobile device user to a unique SIM card hardware identifier of a SIM card of a mobile device of the mobile device user; associating, by the fraud prevention computer and in an electronic registry and in response to a funding source link request, a mobile device user identifier with transaction account information of the mobile device user, the unique SIM card hardware identifier of the SIM card of the mobile device, and a unique mobile device hardware identifier; encrypting, by the fraud prevention computer, the transaction account information; storing, by the fraud prevention computer, the transaction account information; linking, by the fraud prevention computer, a stand-in token to the transaction account information; storing, by the fraud prevention computer, the stand-in token in the SIM card; transmitting, by the fraud prevention computer, public key data of a public key to a memory location of the SIM card, wherein the public key data is securely stored in the memory location of the SIM card; transmitting, by the fraud prevention computer, private key data of a private key to the memory location of the SIM card, wherein the private key data is securely stored to the memory location of the SIM card, wherein the SIM card is pre-provisioned with a holding block ready to receive the public key data and the private key data, wherein the private key is linked to a user menu of the mobile device, wherein the user menu requests payment via a transaction request message to create a signed transaction request message; signing, by the fraud prevention computer, the public key and the identifier of the mobile device user with a private master key that corresponds to the public key, to bind the public key and the identifier to a public master key and to create a certificate; receiving, by the fraud prevention computer, the signed transaction request message over a mobile network via a transaction application stored to a memory associated with the mobile device, wherein the private key data is appended to the transaction request message to create a signed message, and wherein the public key data is appended to the signed transaction request message by the transaction application, issuing, by the fraud prevention computer, a verification request, in response to the public key reading the signed transaction request message and a session being initiated; verifying, by the fraud prevention computer and in response to the public key reading the signed transaction request message, that the public key is correct; validating, by the fraud prevention computer, by comparing the mobile device hardware identifier captured with the transaction request message with expected mobile device hardware identifier information stored in the electronic registry and associated with the received public key; validating, by the fraud prevention computer, by comparing the SIM card hardware identifier information captured with the transaction request message with expected SIM card hardware identifier information stored in the electronic registry and associated with the received public key; verifying, by the fraud prevention computer, that the private key data is correct; appending, by the fraud prevention computer, transaction account information of the mobile device user to the transaction request message, wherein the user menu of the mobile device provides merchant identification data to an application; receiving, by the fraud prevention computer and from the mobile device, a validation of the merchant identification data; and transmitting, by the fraud prevention computer, the appended transaction request to a financial transaction processor for authorization.