05-09-2012, 03:57 PM
A Survey of Applications of Identity-Based Cryptography in Mobile Ad-Hoc Networks
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Abstract
Security in mobile ad-hoc networks (MANETs)
continues to attract attention after years of research. Recent
advances in identity-based cryptography (IBC) sheds light on
this problem and has become popular as a solution base. We
present a comprehensive picture and capture the state of the art
of IBC security applications in MANETs based on a survey of
publications on this topic since the emergence of IBC in 2001. In
this paper, we also share insights into open research problems
and point out interesting future directions in this area.
INTRODUCTION
RESEARCH on security of MANETs remains active, in
spite of years of exploration, in both academia and
industry. It is partially due to the fact that no mature solution
is widely accepted and the growing availability of small,
personalized mobile devices with peer to peer communication
capability through wireless channels.
General security requirements for MANETs include [1]:
Data Confidentiality that keeps data secret to outsiders, Data
Integrity that prevents data from being altered, Data Freshness
that keeps data in the correct order and up-to-date, Data
Availability that ensures data to be available on request, Data
& Identity Authentication that verifies that the data or request
came from a specific, valid sender, and Non-repudiation that
ensures a node cannot deny sending a message.
BACKGROUND
A Brief History of Identity-based Cryptography
Identity-based cryptography schemes are in the category of
“Asymmetric Key based” cryptography. Identity-based cryptography
specifies a cryptosystem in which both public and
private keys are based on the identities of the users. The idea of
IBC was first proposed by Shamir [5] in 1984. Such a scheme
has the property that a user’s public key is an easily calculated
function of his identity, while a user’s private key can be
calculated for him by a trusted authority, called a Private Key
Generator (PKG). The identity-based public key cryptosystem
can be an alternative for certificate-based PKI, especially when
efficient key management and moderate security are required.
Compared to traditional PKI, it saves storage and transmission
of public keys and certificates, which is especially attractive
for devices forming MANETs. Thus, application of IBC in
MANETs is an important research topic in areas of both
cryptography and MANETs.
Discussion and Comments
Table II summarizes the main characteristics and weaknesses
of the master key and private key generation and
distribution schemes.
Table III summarizes the main characteristics and weaknesses
of group key generation and agreement schemes.
Key management is an essential and fundamental service for
ad hoc networks. Secure keys should be set up before other
services can start. This can be achieved by pre-distribution of
keys in network initialization phase. One advantage of IBC key
management is that it saves storage and transmission of public
keys and certificates. Many IBC key management proposals
suggest generating master key and private keys online. There
is a problem in this case. Consider the following scenario:
we need to find a key management scheme to design a secure
routing protocol. Since there is no routing for unicast, the only
way to distribute keys or key shares is broadcast which is not
secure. It turns out to be a group key agreement problem, and
the group key agreement protocol cannot use unicast routing at
that time. Thus key management should not rely on any other
online service if keys are generated online.
CONCLUSIONS
In this survey, we have studied major developments in IBC,
and the applications of IBC in MANETs in various areas. We
have identified the drawbacks and challenges of IBC which
impose difficulties on its application to MANETs.
In the field of MANETs’ security IBC has already been
widely applied. However, we notice there are many issues
unaddressed in these applications.
To apply IBC better in MANETs, we must look at properties
of IBC and identify its pros and cons. On the one hand, some
properties lend IBC attractions to MANETs: private keys are
short and easy to generate and store, public keys are implicitly
carried by their identities, so there is no need to distribute
and store certificates of partners or public key of CA. On the
other hand, its other properties appear awkward in MANETs,
e.g., the problems mentioned in Section VI.