一個以RTCP為基礎的VoIP數位簽章機制

Abstract

隨著網路電話(Voice over Internet Protocol,VoIP)技術的成熟及寬頻網路的普及，VoIP已有逐漸取代傳統PSTN電話的趨勢。VoIP應用大量的數位技術，能達到比傳統PSTN電話更安全的防護，目前已有許多金鑰交換及加密技術被大量應用在實際商品上，但仍缺少在VoIP中加入數位簽章來達到不可否認性的相關規範。我們認為在VoIP中加入數位簽章，必須滿足(1)擁有不可否認性(2)不影響通話品質，必須有很小的傳送端延遲(3)即使在低階手持裝置上也能運行的低運算工作負載(4)不佔用太多頻寬這四項需求，在研究數種串流簽章後，我們將Efficient Multi-chained Stream Signature(EMSS)加入VoIP中。EMSS運用在VoIP上可滿足前三項需求，但在頻寬使用上仍有改進空間。我們進一步提出一個根據RTCP動態調整EMSS參數的機制，經實驗驗證，在犧牲少許驗證率(4%以下)為條件之下，可以節省約6%~15%以上的頻寬。

With the maturity of VoIP (Voice over Internet Protocol, VoIP) technology and the popularity of broadband Network , VoIP has the trends of replacing traditional PSTN phone gradually . VoIP applies a great deal of digital technologies, that can achieve more security protection than traditional PSTN phone, there are many key exchange mechanism and encryption technology has been widely used in the actual goods, but still lacking of some purposals to achieve non-repudiation through digital signatures . We believe that the digital signature suited for VoIP, must be met (1) non-repidiation (2) low sender delay (3)low workload (4) low communication overhead, In examining a number of streaming signature, we adopt Efficient Multi-chained Stream Signature (EMSS) to join in VoIP. EMSS can satisfy the first three demands, but on the aspect of bandwidth usage, there are still room for improvement. We propose a further mechanism about how to adjust EMSS parameter dynamically based on RTCP(Real-time Transport Control Protocol) ,after the experimental verification, we can save at least 4~16% bandwidth at the cost of less than 4% verification rate.