ad hoc network (VANET ), consisting of a network of vehicles, moving at a
relatively high speed, that communicate among themselves with different
purposes, being the main purpose that of improving security on the road. In
VANET, each vehicle broadcasts a message to nearby vehicles and RSUs every few
hundreds of milliseconds. A vehicle or an RSU may receive hundreds of messages
in a short period. If the messages cannot be processed in time, occurrence of
traffic jams and accidents is possible. Five categories of proposals have
addressed security and privacy concerns in VANETs. The first category is based
on digital signatures combined with anonymous certificates. To cope with the
privacy issue, digital signatures must be combined with short-lived anonymous
certificates. The second category is based on group signatures. This approach
is free from traditional certificate management.
The third category is based on
identity-based cryptography (IBC). In IBC, an entity uses a recognizable
identity as its public key and its private key is generated by a trusted
authority (TA) using a master secret. To achieve privacy, the identity of an
entity is replaced with pseudonyms. This approach is similar to the one based
o25n anonymous certificates. The fourth
category is about the IBV protocol which is based on an ideal tamper-proof device (TPD)
from a heavy certificate management burden to maintain all the anonymous
certificates of all the vehicles.
verification and transmission costs of a group signature are very much higher
than those of a traditional signature.
overheads of signature verification and transmission are very high.
the problem of pseudonym burden.
A new multiple trusted authority one –
time identity based protocol is proposed to solve the mentioned disadvantages
in the existing system. This protocol is based on frequency and attribute –
based aggregate concept. A vehicle in the VANET is able to verify many messages
at 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 data
collector to some extent. A co – operative message authentication protocol is
proposed to elevate the verification burden where each vehicle needs to verify
a small amount of messages. This protocol consists of a root TA, several
lower-level TAs and users. Each lower-level TA is enrolled by the root TA. A
user can register to any lower-level TA and compute a signature on a message if
the user has obtained a private key from the lower-level TA. The signature is
only valid under the user’s identity and the public information of the
lower-level TA. This protocol is resistant to side – channel attacks. The possibility of various attacks and their
corresponding solutions are discussed. Also developed a system analytical model
for analyzing various information about the traffic conditions and carry out
NS2 simulations to examine the key distribution delay and missed detection
ratio of malicious messages, with the proposed key management framework. Instead of ideal TPDs, this protocol only
requires realistic TPDs and hence is more practical.
ü Attribute based encryption scheme is used in this protocol
ü Handle large number of messages
ü Signature based SHA algorithm
a Multi Trusted Authority One Time
Frequency Attribute based Aggregate Signature Scheme (MTA-OTFABAS), a protocol
for secure vehicular communications. This protocol is based on frequency and
attribute based aggregate concept.
MTA-OTFABAS achieves enhanced privacy (i.e., conditional unlink
ability), key escrow freeness, robustness and fast message processing, without
requiring an ideal TPD. Simulations show that our protocol is practical.