A computer-implemented method for establishing a secure communication tunnel between a device and a server is provided. The method comprises the server receiving a session request from the device to establish a secure tunnel. A handshake procedure is carried out to set up an encryption/decryption key for the secure tunnel. The handshake procedure uses a first communication channel from the server to the device. The method also includes sending a component of the handshake procedure to the device via a second communication channel. This component is required by the device to continue the handshake procedure or to commencing use of the secure tunnel established by the handshake procedure.