Application RSA in TSP and NTP Server

[[abstract]]電子文件與 Internet 的普及，使得文件擁有權顯得更為重要。為了證明文件擁有權，我們必須為文件添加時戳憑證（Time Stamp Authentication），時戳憑證通常由一個可信賴的第三機構來提供。當文件擁有權發生爭議時，依時戳憑證內之持有人與時間來判定最先持有者為該文件擁有人。在本篇論文中，我們以 RSA 搭配 MD5 來建立時戳憑證伺服器，提供文件之時戳憑證申請。時戳憑證伺服器需要取得申請時間，加入時戳憑證內，做為文件持有之先後判定。這個時間是重要的，它必須是可信賴的，並且能避免時間受到竄改、偽造。因此，時戳憑證伺服器並不使用本地端時間，而向時間源伺服器（Network Time Protocol）取得時間。目前時間源伺服器之安全驗證機制採密鑰系統，然而密鑰系統具有鑰匙交換上的缺點。在本篇論文中，我們改以 RSA 搭配 MD5 做為安全驗證機制，來提高時間源的安全性。將時間源與時戳憑證伺服器分開由不同機構提供，可避免因時戳憑證伺服器的系統時間遭竄改，而產生的弊端。如此架構使得在時間取得上、在時戳憑證上，都受到密碼系統的安全保護。[[abstract]]In internet society, to prove the ownership of the document is very important since electronic document can not be signed by hand. We must add TSA (Time Stamp Authentication) for a docment to prove the ownership. TSA usually be provided by a trusted third party. When a dispute about the ownership of the document, to decide the ownership of the document by the time which in the time stamp. In this thesis, we implement a TSA server by RSA and MD5. It accepts the request to produce the TSA of a document. The TSA server must get a time for TSA. The time is used to decide the ownership of the document. Therefore, it must be trust. And it can’t be falsified or forged. In our implementation, TSA server does not use the time of local system. It get the time from NTP (Network Time Protocol) server. At present, the secure of NTP server depends on MD5/DES technique. But they was inconvenient in key exchange. In this thesis, we use both RSA and MD5 to provide high secure of time source and cope with the key exchange problem. To divide time source and NTP server to the different party, to falsify the system time of TSA server will not affect the TSA. It is secure to get time and produce TSA by the such skeleton