In some embodiments, a method and apparatus for proving the denial of a
direct proof signature are described. In one embodiment, a trusted
hardware device convinces a verifier that the trusted hardware device
possesses cryptographic information without revealing unique, device
identification information of the trusted hardware device or the
cryptographic information. Once the verifier is convinced that the
hardware device possesses the cryptographic information, the verifier may
issue a denial of signature request to the trusted hardware device,
including at least one compromised direct proof signature. In response,
the trusted hardware device issues a denial of the compromised direct
proof signature by proving to the verifier that a cryptographic key held
by the trusted hardware device was not used to form the at least one
compromised direct proof signature. Other embodiments are described and
claims.