Research On Secure Protocols Of Delay Tolerant Networks

Delay tolerant network is a new type of network technology developed grad-ually in recent years. It is characterized by that messages are transported directly through the wireless connection established by two nodes when they meet each other. Message receiver will store and carry the messages. It forwards the mes-sages out until the destination or another node that can forward the message to the destination is encountered. This kind of store-carry-and-forward networks can not only realize the interconnection of heterogeneous networks, but also can be used to propagation messages in the absence of network infrastructure. Therefore, it has a very broad application prospects. For example, when the local surface communication infrastructure has been severely destroyed by the tsunami, earthquakes or other natural disasters, early rescue workers and emer-gency vehicles can use their own wireless communication devices to communi-cate, and sent the date disaster information to the rescue center over the delay tolerant network. When the infrastructure construction is with high investment and low utilization rate, and difficult to take back the construction cost, delay tolerant network is able to provide Internet access for the region’s education, health care and government applications by making the cars, which shuttle be-tween this region and near cities, to be responsible for storing, carrying and forwarding the users’message of this region.As message propagation requires a number of intermediate nodes to store, carry and forward the data, any intermediate node on the path of information dis-semination has enough time to steal or tamper with the information. In addition, any intermediate node on the delivery path can easily undermine the dissemi-nation mechanisms. For example, in order to save the valuable energy, limited buffer, and precious computation resource, some nodes only receive their own message, but refused to forward information for others. Therefore, compared with traditional networks, delay tolerant networks face more security threats. Currently, almost all the researches are focus on the information dissemination methods. The incentive schemes and the security protocols are just beginning to be studied. As so far, the message propagation path tracking and the key distribution has not been studied. However, most existing incentive schemes simply ignore efforts of nodes involved in message delivery if the message de-livered fails to reach its destination. The majority of security researches cur-rently adopt the identity-based cryptography, but the system faces the identity management and updating difficulties, the key generation center knows all the user keys and other shortcomings. Hence, incentive programs and information security schemes both need more innovations.We study the delay tolerant networks by combining the two problems to-gether. The study includes information confidentiality and data integrity in the process of information transmission, identity and data source authentication, the tracking and revealing method of message delivery path, the strategy of node classification and network structure partitioning, key management scheme and the security information transmission model.The main innovation works of the thesis are briefly summarized as follows:(1) Proposed a secure message transaction protocol based on aggregate signa-ture. By verifying the aggregated signature, an intermediate node makes the decision on whether to forward the message or not. Moreover, the delivery path is recorded by the aggregated signature automatically. The scheme uses the advance payment game to prevent the collusion attacks launched by the intermediate nodes. When fragmentation is needed, hash authentication tree is harnessed to decrease the number of authorization request;(2) Proposed a message delivery path tracking protocol for the delay tolerant networks. The scheme links the intermediate nodes on the same deliv-ery path in accordance with the order of message forwarding using time linking protocol. TTP can figure out all the delivery paths based on the time-linking signing requests and the path searching algorithm presented in the scheme, whether the delivery path reaches the destination or not. Therefore, the proposed scheme enables all nodes having contributed in accordance with the rules can get the corresponding reward, which can stimulate nodes to cooperate one another better;(3) Proposed a secure message transmission protocol with dedicated relay nodes. According to their betweenness, nodes are divided into dedicated relays and general terminals. By setting special relay nodes, the commu- nication opportunities between the terminal nodes and the management center are increased, and moreover the overall administrative overhead can be reduced. Hence, we can use the digital certificate-based scheme to ad-dress security issues in delay tolerant networks. By configuring the relay nodes as merchants servers and setting destination node as payment gate-way, respectively, we introduce SET protocol to solve the security issues of delay tolerant networks;(4) Proposed a public key distribution protocol based on two-channel cryptog-raphy. According to the protocol, the correctness and relativity between the public key and its owner can be ensured by two-channel cryptography if the public keys are directly exchanged among their owners. If a public key is not gotten from its owner, its correctness and the relativity between the public key and its owner can be verified with the algorithm presented in the scheme. We associate the number of the public key that has been vali-dated with the dynamic virtual degree by the dynamic virtual graph defined in the scheme. Furthermore, we prove the proposed protocol is effective by using dynamic virtual graph simulation;(5) Proposed a secure message propagation model based on public key. The model convert the number of public key that a node should maintain, in order to get high delivery speed, into the node’s maximum average de-gree. The actual degree of a node in a certain time step is the function of maximum average degree, time, and node’s walk model. By analyzing the parameters, we find out the number of the public key that a node should maintain in order to obtain the rapid message propagation.