GSM行動通信認證方法之改善

　　　　　GSM無線行動通信正快速成長日愈普及，隨之而來使得網路端之 VLR 對行動臺 MS 之認證工作更形繁重，因此 VLR 與 HLR 之間傳送認證參數的資料量也隨之大增。在文獻上 ， Harn-Lin 及 Lee-Hwang-Yang 曾分別提出引進新演算法來降低傳送認證參數資料量的方 法。本文採用相容於現有 GSM 的標準架構，提出只用 GSM 原有之 A3、A5、A8 等演算法以 大幅降低 VLR 與 HLR 之間的認證參數傳輸量之方法。在本文方法下，對每個 MS 送認時， HLR 只要傳送一次三元組（ R, S, Kc ）給 VLR， 爾後的認證工作即可由 VLR 自行產生新 的三元組（ r, s, kc ），執行認證工作，故可大幅降低 VLR 與 HLR 之間的傳送資料量。 本文並分析比較本文方法、標準方法、Harn-Lin 及 Lee-Hwang-Yang 方法。
　　　　　The GSM wireless mobile communication system is more and more popular. In GSM system, the authentication of the subscriber is the ncecssary process to prevent the illegal mobile station from masquerading. In the standard authentication method, the security related parameters (R, S, Kc)s are generated in AUC/HLR througth the algorithms A3,A8. Since VLR consumes one triplet (R,S,Kc) in the authentication process for every call, VLR will request AUC/HLR to send (R,S,Kc)s frequently. To reduce the traffic of these security related parameters between HLR and VLR, an improved authentication method is proposed in this paper. In this improved method, no new algorithm is introduced, and the modified authentication protocol follows the GSM standard one closely except that, after the first authentication, VLR generates the consequent parameters (r,s,kc).Based on the improved authentication inethod, the security parameter traffic can be reduced significantly at littel cost. The comparison among the methods of this paper, the GSM standard, Harn-Lin and Lee-Hwang-Yang is also addressed.