ECQV自簽名憑證及其延伸應用之研究

A Study on ECQV Self-singed Certificate and Its Extensions

蘇勤文(Su Ching-Wen)

指導教授 ： 左瑞麟

國立政治大學/理學院/資訊科學系/碩士(2018年)

https://doi.org/10.6814/THE.NCCU.CS.021.2018.B02

摘要

Elliptic curve Qu-Vanstone（ECQV）由Daniel等人於2001年提出，為目前眾多系統及標準使用的隱式憑證。隱式憑證確保只有憑證的原始擁有者可以算出相應私鑰，且隱式憑證並不包含簽章，因此可以快速計算，適合用於能力受限的系統設備上。但是我們發現ECQV存在兩個問題。第一個問題，由於隱式憑證不包含簽章的特性，在與對方溝通之前無法驗證用戶是否是正確的對象。第二個問題，由於證書和公鑰是一對一的對應關係，當用戶需要多個密鑰時，他們必須頻繁地與證書頒發機構（CA）溝通，這可能增加傳輸溝通成本。因此本研究提出兩種機制來解決上述問題。代理憑證機制以及憑證更新機制，兩種機制皆可基於原始憑證，自行產生多組公私鑰。代理憑證機制產生的公私鑰可分與他人做使用；憑證更新機制不可分與他人做使用，且生成的憑證具有可驗證性，可證實為原憑證擁有者生成，因此兩個機制可滿足不同的情境。另外我們也針對私鑰的機密性和證書的不可偽造性進行安全性證明。同時我們也透過實作證實，相較RSA或是ECQV我們提出的機制確實可以利用較少的時間、較低的成本生成憑證，因此適用於能力受限系統。

關鍵字

Elliptic curve Qu-Vanstone(ECQV) ； 隱式憑證 ； 憑證更新

並列摘要

Elliptic curve Qu-Vanstone (ECQV) is now the most commonly used implicit certificate. However, we noticed that ECQV presents two main problems. First, due to the characteristics of the implicit certificate, it is not possible to verify whether the user is the correct object until we communicate with. Second, the certificate and the public key are in a one-to-one correspondence; hence, when users need multiple keys, they have to frequently communicate with the Certificate Authority (CA), which may increase the communication transmission costs. Therefore, we propose two schemes to solve the above issues. The proxy certificate scheme allows users to update their public/private keys without asking for a new certificate from the CA. The certificate update scheme allows users to update their keys and verifiers to check their identities. Then we also make sure that our scheme satisfy the confidentiality of the private key and the unforgeability of the certificate. In addition, we also implement the scheme we proposed and proved that it took a short time. Therefore, the mechanism we propose can indeed reduce the cost and suitable for power-limited systems.

並列關鍵字

Elliptic curve Qu-Vanstone(ECQV) ； Implicit certificate ； Certificate update

參考文獻

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