An anonymous attestation cryptographic protocol is provided for enabling a target (device 4) to attest to a predetermined property of the device without needing to reveal its identity to a verifier (8). When obtaining a credential from an issuer (6) to attest to the predetermined property, the credential is validated by an intermediary device (2) which is a separate consumer electronics device to the target device (4) itself. This allows the relatively processor-intensive calculations required for validating the credential to be performed on a separate device (2) from the device (4) for which the attestation has been made, allowing anonymous attestation protocols to be used for lower powered target devices such as sensors in the internet of things.