877 research outputs found
An identity-based key infrastructure suitable for messaging applications
Abstract—Identity-based encryption (IBE) systems are relatively recently proposed; yet they are highly popular for messaging applications since they offer new features such as certificateless infrastructure and anonymous communication. In this paper, we intended to propose an IBE infrastructure for
messaging applications. The proposed infrastructure requires one registration authority and at least one public key generator and they secret share the master secret key. In addition, the PKG also shares the same master secret with each user in the system in a different way. Therefore, the PKG will never be able to learn the private keys of users under non-collusion assumption. We discuss different aspects of the proposed infrastructure such as security, key revocation, uniqueness of the identities that constitute the main drawbacks of other IBE schemes. We demonstrate that our infrastructure solves many of these drawbacks under certain assumptions
Group key establishment protocols: Pairing cryptography and verifiable secret sharing scheme
Thesis (Master)--Izmir Institute of Technology, Computer Engineering, Izmir, 2013Includes bibliographical references (leaves: 97-103)Text in English; Abstract: Turkish and Englishx, 154 leavesThe aim of this study is to establish a common secret key over an open network for a group of user to be used then symmetrical secure communication between them. There are two methods of GKE protocol which are key agreement and key distribution. Key agreement is a mechanism whereby the parties jointly establish a common secret. As to key distribution, it is a mechanism whereby one of the parties creates or obtains a secret value and then securely distributes it to other parties. In this study, both methods is applied and analyzed in two different GKE protocols. Desirable properties of a GKE are security and efficiency. Security is attributed in terms of preventing attacks against passive and active adversary. Efficiency is quantified in terms of computation, communication and round complexity. When constructing a GKE, the challenge is to provide security and efficiency according to attributed and quantified terms. Two main cryptographic tools are selected in order to handle the defined challenge. One of them is bilinear pairing which is based on elliptic curve cryptography and another is verifiable secret sharing which is based on multiparty computation. In this thesis, constructions of these two GKE protocols are studied along with their communication models, security and efficiency analysis. Also, an implementation of four-user group size is developed utilizing PBC, GMP and OpenSSL Libraries for both two protocols
A New Cryptosystem Based On Hidden Order Groups
Let be a cyclic multiplicative group of order . It is known that the
Diffie-Hellman problem is random self-reducible in with respect to a
fixed generator if is known. That is, given and
having oracle access to a `Diffie-Hellman Problem' solver with fixed generator
, it is possible to compute in polynomial time (see
theorem 3.2). On the other hand, it is not known if such a reduction exists
when is unknown (see conjuncture 3.1). We exploit this ``gap'' to
construct a cryptosystem based on hidden order groups and present a practical
implementation of a novel cryptographic primitive called an \emph{Oracle Strong
Associative One-Way Function} (O-SAOWF). O-SAOWFs have applications in
multiparty protocols. We demonstrate this by presenting a key agreement
protocol for dynamic ad-hoc groups.Comment: removed examples for multiparty key agreement and join protocols,
since they are redundan
Still Wrong Use of Pairings in Cryptography
Several pairing-based cryptographic protocols are recently proposed with a
wide variety of new novel applications including the ones in emerging
technologies like cloud computing, internet of things (IoT), e-health systems
and wearable technologies. There have been however a wide range of incorrect
use of these primitives. The paper of Galbraith, Paterson, and Smart (2006)
pointed out most of the issues related to the incorrect use of pairing-based
cryptography. However, we noticed that some recently proposed applications
still do not use these primitives correctly. This leads to unrealizable,
insecure or too inefficient designs of pairing-based protocols. We observed
that one reason is not being aware of the recent advancements on solving the
discrete logarithm problems in some groups. The main purpose of this article is
to give an understandable, informative, and the most up-to-date criteria for
the correct use of pairing-based cryptography. We thereby deliberately avoid
most of the technical details and rather give special emphasis on the
importance of the correct use of bilinear maps by realizing secure
cryptographic protocols. We list a collection of some recent papers having
wrong security assumptions or realizability/efficiency issues. Finally, we give
a compact and an up-to-date recipe of the correct use of pairings.Comment: 25 page
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