There is described a challenge-response method for a client device. The method comprises steps of: (a) receiving challenge data, wherein the challenge data is content encrypted using an encryption key, the content including a nonce; (b) using a secured module of the client device to access the content by decrypting the challenge data using a decryption key of the secured module, the decryption key corresponding to the encryption key; (c) processing a version of the content output by the secured module so as to obtain the nonce; and (d) providing the nonce as a response. There is also described a client device for implementing the above challenge-response method. There is also described a computer program which, when executed by a processor, causes the processor to carry out the above challenge-response method. Finally, there is described a computer readable medium storing the above-mentioned computer program.