1. A method comprising: associating, by a fraud prevention computer and in an electronic registry, a mobile device user identifier with transaction account information of a mobile device user, a unique SIM card hardware identifier of a SIM card of a mobile device, and a unique mobile device hardware identifier, transmitting, by the fraud prevention computer, public key data 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 to the memory location of the SIM card, wherein the private key data is securely stored to the memory location of the SIM card; receiving, by the fraud prevention computer, a 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 message by the transaction application; verifying, by the fraud prevention computer, 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; and transmitting, by the fraud prevention computer, the appended transaction request to a financial transaction processor for authorization.