Existing different purposes, being the main purpose

ExistingSystem: Vehicularad hoc network (VANET ), consisting of a network of vehicles, moving at arelatively high speed, that communicate among themselves with differentpurposes, being the main purpose that of improving security on the road.

InVANET, each vehicle broadcasts a message to nearby vehicles and RSUs every fewhundreds of milliseconds. A vehicle or an RSU may receive hundreds of messagesin a short period. If the messages cannot be processed in time, occurrence oftraffic jams and accidents is possible. Five categories of proposals haveaddressed security and privacy concerns in VANETs. The first category is basedon digital signatures combined with anonymous certificates. To cope with theprivacy issue, digital signatures must be combined with short-lived anonymouscertificates.

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The second category is based on group signatures. This approachis free from traditional certificate management. The third category is based onidentity-based cryptography (IBC). In IBC, an entity uses a recognizableidentity as its public key and its private key is generated by a trustedauthority (TA) using a master secret. To achieve privacy, the identity of anentity is replaced with pseudonyms. This approach is similar to the one basedo25n anonymous certificates.  The fourthcategory is about the IBV protocol which is based on an ideal tamper-proof device (TPD) Disadvantages:  ü  Suffersfrom a heavy certificate management burden to maintain all the anonymouscertificates of all the vehicles.  ü  Theverification and transmission costs of a group signature are very much higherthan those of a traditional signature.

  ü  Theoverheads of signature verification and transmission are very high.  ü  Experiencesthe problem of pseudonym burden.Proposed System:A new multiple trusted authority one –time identity based protocol is proposed to solve the mentioned disadvantagesin the existing system. This protocol is based on frequency and attribute –based aggregate concept. A vehicle in the VANET is able to verify many messagesat the same time and all their signatures can be compressed as a single unit.This paves way to reduce the storage space required by a vehicle or a datacollector to some extent.

A co – operative message authentication protocol isproposed to elevate the verification burden where each vehicle needs to verifya small amount of messages. This protocol consists of a root TA, severallower-level TAs and users. Each lower-level TA is enrolled by the root TA. Auser can register to any lower-level TA and compute a signature on a message ifthe user has obtained a private key from the lower-level TA.

The signature isonly valid under the user’s identity and the public information of thelower-level TA. This protocol is resistant to side – channel attacks.  The possibility of various attacks and theircorresponding solutions are discussed. Also developed a system analytical modelfor analyzing various information about the traffic conditions and carry outNS2 simulations to examine the key distribution delay and missed detectionratio of malicious messages, with the proposed key management framework. Instead of ideal TPDs, this protocol onlyrequires realistic TPDs and hence is more practical.Advantages:  ü   Attribute based encryption scheme is used in this protocol  ü   Handle large number of messages   ü   Signature based SHA algorithmConclusion:                Proposeda Multi Trusted Authority One TimeFrequency Attribute based Aggregate Signature Scheme (MTA-OTFABAS), a protocolfor secure vehicular communications.

This protocol is based on frequency andattribute based aggregate concept.MTA-OTFABAS achieves enhanced privacy (i.e., conditional unlinkability), key escrow freeness, robustness and fast message processing, withoutrequiring an ideal TPD. Simulations show that our protocol is practical.