- 學位論文
改良UMTS認證機制之研究
A Study on the Improvement of Authentication Mechanisms for UMTS
摘要
摘要 在本論文中，我們主要針對全球行動電信系統(UMTS)提出兩個基於對稱性與非對稱性之新的認證協定，此認證協定不但符合目前UMTS規格需求，而且改善了UMTS在認證過程中安全上之不足。 第一個新的改良認證協定是基於對稱式密碼系統，此系統中MS與HLR之間擁有共同的祕密金鑰，且VLR與HLR之間也擁有共同之祕密金鑰，並在認證過程當中完成了祕密金鑰與暫時行動用戶身份(TMSI)之更新。 第二個新的改良認證協定是基於非對稱式密碼系統，此系統由證書服務者來提供電子證書給HLR，而HLR擁有MS與VLR的電子證書，並在認證過程中完成三方雙向認證和MS公開金鑰的更新。此外，我們所提出之兩個新的安全協定經分析均能夠達到安全性的需求和威脅的準則與目標。 在本論文中，我們主要的貢獻如下: (1)第一個方案達到三方之間的單向認證和第二個方案達到三方之間的雙向認證，此兩個方案都比全球行動電信系統都更加安全。(2)此兩個方案均能阻檔多種的攻擊。 (3)此兩個方案不但可以保護用戶傳送的資料，而且可以保有用戶身份的機密性。 我們相信本論文的研究成果，對未來行動通訊認證的研究領域上有相當的助益。
關鍵字
第三代行動通訊認證並列摘要
Abstract In this thesis, we propose two new authentication protocols for UMTS (Universal Mobile Telecommunication System) based on symmetric and asymmetric cryptosystems, respectively. The comparison of performance between protocols of UMTS and our proposed schemes are also made. The two new authentication protocols not only conform to specification of UMTS, but also improve the insufficient security of the published authentication protocol of UMTS. The first mechanism is based on symmetric-key encryption functions that the cost and complexity of hardware design may be implicitly reduced. In addition, it provides all the requirements of an authentication protocol. The characteristic of the first scheme is that the MS(Mobile Station)and the HLR (Home Location Register)have a common secret key and the VLR(Visitor Location Register)and the HLR possess another common secret key, respectively. At first, MS sends a random number RM and his TMSI (Temporary Mobile Subscriber Identity) to VLR and HLR. The design to use TMSI can protect the subscriber’s true identity, and RM is applied to challenge VLR and HLR. Then, HLR generates a random number RH to VLR and MS, respectively. In addition to challenge VLR and MS, the random number RH is also used to execute the task of key refreshment. At the same time, it can accomplish key exchange between MS and VLR, and identity authentication of the MS to VLR. Finally, when the MS and HLR send the response messages to VLR, VLR can authenticate the identity of MS to check if MS is a legal user. The second mechanism is based on asymmetric-key encryption function that it is able to solve an important problem of key management and distribution, it also provides non-repudiation of part of the transmitted data. The characteristic of the second scheme is that HLR have certificates of MS and VLR, and VLR can obtain the public key of MS to be sent by HLR. Similarly, the MS can obtain the public key of VLR to be sent by HLR. First, MS uses secret message to challenge the HLR and VLR, and VLR also uses secret message to challenge the HLR. However, secret message is encrypted with its private key. After the HLR and VLR decrypting the secret message to response MS based on MS’s public key, HLR also decrypts secret message to response VLR based on VLR’s public key. If the processes are finished, they can achieve mutual authentication between all participants, and refresh MS’s public key. Finally, when the MS and HLR send the response messages to VLR, VLR can authenticate the identity of MS to check if MS is a legal user and refresh his TMSI. To summarize, the contributions of our improved schemes are as follows: (1)Bi-unilateral authentication among MS、VLR and HLR in the first scheme and entire mutual authentication between all participants in the second scheme are achieved. It makes a more secure communication environment than UMTS authentication protocol (2) The schemes can prevent many kinds of attacks. (3) Not only it can protect user data, but also provides confidentiality of user identity. It is believed that the results of our study in this thesis will be much helpful to the future research in the areas of the authentication protocols of UMTS.