雲端聯盟（Cloud Federation）是聯合兩個或兩個以上服務提供者（Service Provider）組成之聯盟，在相同聯盟內的服務提供者會對其他服務提供者提出服務的請求，由所有提供服務之服務提供者以及使用者所組成之聯盟。
當使用者（Client）對服務提供者提出服務請求時，服務提供者會對其請求提供服務。根據使用者提出之服務請求，若無法完成，則轉發給其他服務提供者，由同個聯盟下其他的服務提供者，提供相對應之資料或服務，使用者僅需對單一服務提供者提出服務請求，不需要對應到其他服務提供者。
傳統上使用者對服務提供者提出請求，服務提供者會保留日誌檔，來記錄服務的過程，但日誌檔是不安全的。日誌檔的產生沒有經過密碼學的保護，也沒有雙方的確認，可能會遭受服務提供者竄改，使用者無法驗證日誌檔的正確性。當使用者提出服務請求，服務提供者將請求轉發給其他服務提供者，使用者無法得知服務提供者與其他服務提供者溝通之記錄，若發生問題則使用者無法得知是哪個環節出現問題，服務提供者無法提出可信的證明，來證明自己是正確的。
為了要證明違約，我們定義一個協定來規範服務提供者及使用者，我們稱為加密問責協定（Cryptographic Accountability Protocols），在本文中我們簡稱為CAP。我們要求服務提供者要保留每次的動作並留下雙方不可否認的證據，使用者需要留下最後一筆與服務提供者溝通的證據。若發生問題，可利用使用者手中證據來稽核[1]服務提供者，來確保整個系統的正確性。
我們先利用舊有的證明違約技術來實作[10]，在實作的過程中會產生無法稽核的情況及將證明違約技術應用於雲端聯盟上會產生新的問題，我們提出新的架構應用於雲端聯盟上，來解決遇到的問題。

關鍵字：雲端聯盟、違約證明、即時稽核

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Submitted to journal for publication (in revision)
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