隨著數位服務的蓬勃發展，服務提供者必須先確認使用者平台的可信賴性 (Trustworthiness)，以避免使用者對數位服務做未經授權的轉移或分享。可信賴計算組織 (Trusted Computing Group) 一直致力於推廣使用者藉由一個防竄改 (Tamper-resistant) 的硬體安全模組，稱作可信賴平台模組 (Trusted Platform Module) 建立可信賴計算平台 (Trusted Platform)，以保護服務提供者的數位財產權。可信賴平台模組被安裝在使用者平台的主機板上，並且執行平台狀況與軟體完整性的測量，將測量的結果儲存於其內部暫存器之中。

遠端證實協定 (Remote Attestation) 得以讓服務提供者要求使用者提出由可信任平台模組執行的檢查結果，並且利用此結果來評估使用者平台的可信任性。然而，一般的遠端證實協定並沒有考量使用者的隱私性，使得服務提供者可以在網路上追蹤使用者的行蹤，甚至連結使用者在網路上的身分。

直接匿名遠程證實協定 (Direct Anonymous Attestation) 是由Brickell等人所提出，是一項能達到匿名性並且不需要線上公正第三方協助的解決方案。 然而Brickell等人所提出的解決方案對計算能力受限的可信賴平台模組而言，其計算複雜度甚鉅。學者陳提出了輕量化可信賴平台模組的直接匿名遠程證實協定。在本論文中，我們承襲了陳的精神，持續對可信賴平台模組的計算進行簡化，最後得到一個可信賴平台模組計算複雜度需求遠低於陳的方案之新協定。

With rapid development of electronic service, service provider must confirm user's computing platform whether it is trustworthy that protects digital product from being abused.

Trusted computing group makes efforts to establish a trusted computing platform through a tamper-resistant cryptographic chip, namely trusted platform module (TPM). The TPM, which is embedded on the motherboard of a host platform, measures the software and hardware configurations and stores the measurement results in internal registers. Remote attestation enables a
verifier (i.e., service provider) to request a prover (i.e., user's computing platform with TPM) which returns the measurement results used for justifying the trustworthiness.
However, a classical remote attestation scheme did not considerthe user's privacy that allows the verifier to learn information about all user's transactions on the Internet.


Direct anonymous attestation (DAA) scheme, which was first proposed by Brickell et al., is a promising solution used to address the privacy issues without employing an on-line trusted third party (i.e., an on-line certificate authority). However,the Brickell et al. DAA scheme incurs a considerably computational overhead for a resource-constraint TPM. Chen proposed a lightweight DAA scheme requiring less TPM
computation. In this thesis, we propose an improved DAA scheme based on the Chen's DAA scheme, and our proposed DAA scheme is more efficient than the Chen's DAA scheme in computational complexity of the TPM.

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