An integrated circuit is disclosed for selectively encrypting plaintext data received from a first device to produce encrypted data to send to a second device. The integrated circuit comprises controllable encryption circuitry comprising a data input, an enable input, and a data output. The integrated circuit further comprises a plaintext input for providing the plaintext data to the data input, an encrypted text output for providing the encrypted data from the data output, and a first control input for receiving a first device authentication signal for authenticating the first device. The integrated circuit further comprises a verification circuit responsive to the first device authentication signal for producing a first verification signal for use in controlling the enable input of the encryption circuitry to enable the encryption circuitry to provide the encrypted data via the encrypted text output.