| Summary: | 碩士 === 樹德科技大學 === 資訊工程學系 === 93 === Holding electronic conferences via mobile devices such as PDAs or mobile phones in an open wireless communication environment makes security problems such as eavesdropping and interception more susceptible. To avoid the vicious attack of illegal users while the conference is held, conference participants should share a conference key before the conference begins. For secure communication, those participates in the conference can use a conference key to encrypt or decrypt transmitted data to avoid illegal users’ masquerade.
In a wireless communication environment, three elements should be taken into consideration: the computational power of mobile devices, the frequency of interactive communications, and the secure communications. In this thesis, three different types of conference key distribution protocol will be discussed respectively based on the three elements mentioned.
The fist type is a conference key distribution protocol without a trusted center. Yan, Chang, and Hwang in 2003 proposed an efficient and anonymous conference key distribution protocol, which is based on elliptic curve discrete logarithm problem and the properties of the line. This protocol distributes a conference key effectively to legal and anonymous conference participants and enables them to hold a secure electronic conference. However, we find that the Yan-Chang-Hwang protocol exists counting errors in its analysis of computational complexity. We will fix their errors and further propose a modified conference key distribution protocol with anonymity and efficiency.
The second type is a conference key distribution protocol with a trusted center and using public-key encryption. In 2003 Chee, Siew and Tan proposed a secure and efficient conference scheme for mobile communications based on modular square root technique. This scheme reduces a modular exponential computation, which is required when portable device uses public key cryptography to communicate with the trusted center confidentially. In this thesis, we will propose a new conference key distribution protocol based on pre-computation. In comparison with the Chee-Siew-Tan protocol, our proposed protocol has less computational overheads for portable devices.
The third type is a conference key distribution protocol with a trusted center and using private-key encryption. Hwang and Chang in 2003 proposed such a protocol with the property of self-encryption, in which the computational complexity of the mobile device is reduced. In this thesis, we propose a more efficient protocol than the Hwang-Chang protocol. Our proposed protocol reduces the frequency of interactive communications between the participants and the trusted center.
In this thesis, we propose three types of conference key distribution protocols. Our proposed protocols distribute conference keys with efficiency and security for mobile communications.
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