The direct anonymous attestation proposed by Brickell adopts an anonymous scheme which is "all or none" for verifiers

and the direct anonymous scheme is applicable for only a few scenarios

which can not satisfy the needs in several cases.To design a flexible anonymous scheme becomes a critical issue for deploying the trusted computing platform.We analyze the problems of the anonymous scheme and propose the direct anonymous scheme with sub-group privacy enhancement properties.This proposed scheme provides the privacy solution for the small group

of which we propose two schemes and analyze the performance and security.