A system implements a secure transaction of data between a server and a remote device. The remote device comprises: processing means adapted to process input data according to a security process; data storage means adapted to store verification information derived from the input data according to an encryption algorithm; and communication means for communicating the input data which has been processed by the security process to the server. The server is adapted to transmit a verification request to the remote device, and to verify the integrity of the security process based on verification information received from the communication means of the remote device in response to the verification request.