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The Attestation Mechanism in Trusted Computing. Platform. 4) Cert AIK { PK A , #A}, Cert CA { PK AIK }. Application A. Verifier. generates PK A & SK A. 5) verifies the signatures. 6) looks up #A in DB. 7). 1) PK A. 3) Cert{PK A , #A}SK AIK. #A. “ok”. TPM. 2) computes hash #A. DB.
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Platform 4) CertAIK{PKA, #A}, CertCA{PKAIK} Application A Verifier generates PKA & SKA 5) verifies the signatures 6) looks up #A in DB 7) ... 1) PKA 3) Cert{PKA, #A}SKAIK #A “ok” TPM 2) computes hash #A DB PKTPM & SKTPM (Endorsement key) PKAIK & SKAIK (Attestation Identity Key) A Simple Remote Attestation Protocol
Privacy Concerns • The attestation key could be used to track internet activity and compromise privacy. • 1st solution: trusted third party. • 2nd solution: Direct anonymous attestation. -E. Brickell, J. Camenisch, and L. Chen
DAA - Joining Platform 2) DAA, CertCA{PKTPM} DAA Issuer TPM 1) generates DAA key key=(a,b,d,n) PKTPM & SKTPM (Endorsement key) 3) SigIssuer(DAA) *SigIssuer(DAA) is (c,e,s) such that ce = adaa bs d mod n
DAA – Attestation (1) 1) Generate AIKi 2) Compute #A Platform 3) Compute SigDAA{AIKi, verifier, time} 4) SigAIKi{PKA, #A} Application A Verifier TPM PKTPM & SKTPM (Endorsement key) PKAIKi & SKAIKi (Attestation Identity Keys) DAA key
DAA – Attestation (2) 1) Generate AIKi 2) Compute #A Platform 3) Compute SigDAA{AIKi, verifier, time} 4) SigAIKi{PKA, #A} Application A Verifier TPM 5) ZKP that establishes that the TPM posesses: SigIssuer{DAA} and SigDAA{AIKi, verifier, time} PKTPM & SKTPM (Endorsement key) PKAIKi & SKAIKi (Attestation Identity Keys) DAA key