DAA-A: Direct Anonymous Attestation with Attributes

The TPM 2.0 specification has been designed to support a new family of Elliptic Curve (EC) based Direct Anonymous Attestation (DAA) protocols. DAA protocols are limited to anonymous or pseudonymous attestations. But often a more flexible attestation would be needed. For instance, attesting that the platform is a certain model from a certain vendor. Such an attestation would require to bind the attributes model and vendor to the TPM. This paper shows how the DAA protocols can be augmented with an arbitrary number of attributes. This gives a new family of protocols called DAA-A, which means DAA with attributes. In a DAA-A protocol, the user of the TPM/platform can select which attributes he will show to the verifier and which attributes he will hide. The authenticity of the hidden attributes will be proved by a zero knowledge protocol. The DAA-A protocols have user controlled linkability in the same way as the DAA protocols. We show explicitly, how the two most prominent EC based DAA protocols for TPM 2.0 can be extended to DAA-A protocols.