群體導向的並行簽章協定

　　　　　本文利用影子金匙與並行處理的觀念，提出一個數位聯合簽章的作業協 定，目的在改進以往聯合簽章的做法上，由於簽章的成員之間，不論是依固定順 序或採無固定順序，都必需進行連續簽章之處理，形成聯合簽章作業時間上的消 耗;甚至容易因任何簽名成員故意遲滯簽名動作，而影響聯合簽章作業進行的缺 失。故本文運用機密分享方式，建立影子全匙與訊息認証程序，提出(n,n)門檻式 簽章，藉此以達成聯合簽章可在同一時間內，利用文件廣播方式，由各簽名者同 步進行簽章，以獲取作業時效之改進。此外，為防止簽名者任意妨礙簽章的進行， 在本文中亦提出(t,n)門檻式簽章的方法。本文所提兩項聯合簽章的方法，均是建 立在離散對數的困難度上，故方法具高度的安全性。
　　　　　This paper presents a concurrent protocol for digital multisignatures. The proposed protocolis developed on the concepts of shadow key and concurrent processing. The objective is tosimplify the process of signature. A sequential process of signatures among members is alwaysrequired, no matter whether the group- oriented multisignature is done in a fixed order or not,a disadvantage of time consuming is inevitable and is worthy to improve; besides, the processof signatures is even vulnerable to members who may purposely not be cooperative for signature, the process of multisignature can then be postponed. So a (n, n) threshold digital signature scheme is provided first. The proposed (n, n) threshold digital signature is established onthe concept of secret sharing. The shadow key and message authentication are applied so thatthe group-oriented multisignature can be concurrently done among members. An effect of timeimprovement can then be found. Secondly, in order to prevent the influence of purposefuldisturbance, a (t, n) threshold digital signature scheme is also provided. Both the proposedmultisignature methods are secure due to the difficulty of solving the discrete logarithm problem. The proposed methods are believed to have a high degree of security.