Study On Delay Tolerant Networks And Security Key Technologies

Delay tolerant networks (DTNs) which are mainly applied to the environments thatsuffered from high latency, intermittent connectivity, and high error rate, are born in theexploration of deep space. DTNs exhibit great potential in military networking, disasterrelief, and species tracking. However, the architecture of overlay layers makes DTNshardly avoid the traditional security threats. The constraints of the deployed environmentandnodecapacityconstraintsinenergy,storage,computationalpowerandcommunicationpower make the classical security technologies not be applied in challenged environment.With the advancement of applications in space missions and terrestrial operation, securityissues, such as the modification of bundles, the selfish behavior, become the bottleneckrestricting the development of DTNs. In conclusion, the research on DTNs and the keytechnologies is curial issue to improve the security architecture.Integrated with various types of application demands and development trends, wefocus on DTNs and security issues, such as secret sharing, evaluation of protocol perfor-mance, reputation schemes and security route. The contribution can be summarized asfollowing:1. The secret sharing algorithm in DTNs. According to the vulnerability in Shamir’sthreshold-based secret sharing algorithm, we analyze the problems in the communicationsteps and computing power for complete shuffling algorithm, and propose a partial shuf-fling algorithm. According to the dynamic randomness through the introduction of feed-back time, a dynamic shuffling queue is designed, which reduces the steps of intercom-munication in the process of secret sharing, and make our proposal suitable for challengednetworks. A dynamic correction mechanism is presented to avoid repetitive calculationsand frequent interactions. The mechanism reduces consumption of bandwidth and re-sources, and improves the efficiency of secret sharing. The time consumption model isproposed to verify the validity of our algorithm.2. The derivation of direct transmission probability for the RWP model. Accordingto the modeling of direct transmission behavior in the RWP model, the direct transmis-sion probability between nodes turns into the probability that the distance between nodesis less than the coverage of wireless devices under a deterministic spatial distribution. On the basis of the research on spatial distribution, the cumulative distribution functionand the probability density function of the distance between nodes are derived from one-dimensional to two-dimensional and from the unit area to the general region. In order tosimplify the calculation, a polynomial fitting is performed on the Matlab platform, and afittingformulaoforder4isobtainedtoapproximatetheoriginalequation. Thecorrectnessof the fitting formula is verified on the Mathematica platform.3. The reputation models and incentive scheme for DTNs. In order to monitoringneighboring nodes’ behavior in challenged environments, the concept of forwarding cre-dential is introduced, and an observation protocol is presented, which make the behaviorobservation get rid of the dependence on promiscuous listening mode and source rout-ing mode. The beta reputation model is presented to assess the trustworthiness of nodes,and several classic attack, e.g. unreliable service attack, spoofing attack, ballot attack andbad-mouthing attack, are tested to prove the effectiveness of the beta model. For differ-ent application requirements, a reputation model based on matrix calculation is presented.Through the direct matrix computation, the assessment process is optimized. In order toimprove the flexibility of the rating on nodes’ behavior, a novel model of variable rat-ings on the quality of service is proposed. Nodes give rating on others according to thequality of forwarding, which takes place of the recording of the frequency of service. Apractical reputation-based incentive scheme, named PRI, is presented, and an applicationframework of PRI scheme is given. On the ONE simulation platform, the reputation mod-els and the PRI scheme is verified, and the optimized configuration of forwarding copynumber and the effect of network load on performance are discussed.4. An enhanced binary spray and wait scheme. Oriented to the spray and wait pro-tocol which is widely recognized in DTNs, we propose an enhanced binary SW routingprotocol. Ourproposaladdressestheselfishnessthatresultsinthedeteriorationofnetworkperformance or even unavailable. On the basis of probability calculation, a variable deci-sion criterion takes place of complex computation formula to reduce the burden on nodes’computation power. Compared to binary SW routing protocol, our protocol is verified toalleviate the hazard of selfishness, and effectively improve the network performance.Insummary,accordingtothesecuritythreatsandrequirements,withtheaimofDTNsandsecuritykeytechnologies,andtakingtheuniquecharacteristicsofchallengedenviron-ments into consideration, this thesis focuses on improvement and innovation of security protocols and mechanisms. Along with the deepening of application in environmentalmonitoring, military strategy, deep space exploration, counter-terrorism security, earth-quake monitoring, underwater exploration, disaster relief, the research of this subject notonly promote the process of practicality, but also have important theoretical value in thedevelopments of security in DTNs.