17 research outputs found
Secure pairing-free two-party certificateless authenticated key agreement protocol with minimal computational complexity
Key agreement protocols play a vital role in maintaining security in many critical applications due to the importance of the secret key. Bilinear pairing was commonly used in designing secure protocols for the last several years; however, high computational complexity of this operation has been the main obstacle towards its practicality. Therefore, implementation of Elliptic-curve based operations, instead of bilinear pairings, has become popular recently, and pairing-free key agreement protocols have been explored in many studies. A considerable amount of literatures has been published on pairing-free key agreement protocols in the context of Public Key Cryptography (PKC). Simpler key management and non-existence of key escrow problem make certificateless PKC more appealing in practice. However, achieving certificateless pairing-free two-party authenticated key agreement protocols (CL-AKA) that provide high level of security with low computational complexity, remains a challenge in the research area. This research presents a secure and lightweight pairingfree CL-AKA protocol named CL2AKA (CertificateLess 2-party Authenticated Key Agreement). The properties of CL2AKA protocol is that, it is computationally lightweight while communication overhead remains the same as existing protocols of related works. The results indicate that CL2AKA protocol is 21% computationally less complex than the most efficient pairing-free CL-AKA protocol (KKC-13) and 53% less in comparison with the pairing-free CL-AKA protocol with highest level of security guarantee (SWZ-13). Security of CL2AKA protocol is evaluated based on provable security evaluation method under the strong eCK model. It is also proven that the CL2AKA supports all of the security requirements which are necessary for authenticated key agreement protocols. Besides the CL2AKA as the main finding of this research work, there are six pairing-free CL-AKA protocols presented as CL2AKA basic version protocols, which were the outcomes of several attempts in designing the CL2AKA
Security in Key Agreement: Two-Party Certificateless Schemes
The main goal of cryptography is to enable secure communication over a public channel; often a secret shared among the communicating parties is used to achieve this. The process by which these parties agree on such a shared secret is called key agreement. In this thesis, we focus on two-party key agreement protocols in the public-key setting and study the various methods used to establish and validate public keys. We pay particular attention to certificateless key agreement schemes and attempt to formalize a relevant notion of security. To that end, we give a possible extension of the existing extended Canetti-Krawzcyk security model applicable to the certificateless setting. We observe that none of the certificateless protocols we have seen in the literature are secure in this model; it is an open question whether such schemes exist. We analyze several published certificateless key agreement protocols, demonstrating the existence of key compromise impersonation attacks and even a man-in-the-middle attack in one case, contrary to the claims of the authors. We also briefly describe weaknesses exhibited by these protocols in the context of our suggested security model
Pairing-based cryptosystems and key agreement protocols.
For a long time, pairings on elliptic curves have been considered to be destructive in elliptic curve cryptography. Only recently after some pioneering works, particularly the well-known Boneh-Franklin identity-based encryption (IBE), pairings have quickly become an important
tool to construct novel cryptographic schemes.
In this thesis, several new cryptographic schemes with pairings are proposed, which are both efficient and secure with respect to a properly defined security model, and some
relevant previous schemes are revisited.
IBE provides a public key encryption mechanism where a public key can be an arbitrary string such as an entity identifier and unwieldy certificates are unnecessary. Based on the Sakai-Kasahara key construction, an IBE scheme which is secure in the Boneh-Franklin IBE model is constructed, and two identity-based key encapsulation mechanisms are proposed. These schemes achieve the best efficiency among the existing schemes to date. Recently Al-Riyami and Paterson introduced the certificateless public key encryption (CL-PKE) paradigm, which eliminates the need of certificates and at the same time retains the desirable properties of IBE without the key escrow problem. The security formulation of CL-PKE is revisited and a strong security model for this type of mechanism is defined.
Following a heuristic approach, three efficient CL-PKE schemes which are secure in the defined strong security model are proposed. Identity-based two-party key agreement protocols from pairings are also investigated.
The Bellare-Rogaway key agreement model is enhanced and within the model several previously unproven protocols in the literature are formally analysed. In considering that the user identity may be sensitive information in many environments, an identity-based key agreement protocol with unilateral identity privacy is proposed
Cryptographic Schemes based on Elliptic Curve Pairings
This thesis introduces the concept of certificateless public key
cryptography (CLPKC). Elliptic curve pairings are then used to
make concrete CL-PKC schemes and are also used to make other
efficient key agreement protocols.
CL-PKC can be viewed as a model for the use of public key cryptography
that is intermediate between traditional certificated PKC and ID-PKC.
This is because, in contrast to traditional public key cryptographic
systems, CL-PKC does not require the use of certificates to guarantee
the authenticity of public keys. It does rely on the use of a trusted
authority (TA) who is in possession of a master key. In this
respect, CL-PKC is similar to identity-based public key
cryptography (ID-PKC). On the other hand, CL-PKC does not suffer
from the key escrow property that is inherent in ID-PKC.
Applications for the new infrastructure are discussed.
We exemplify how CL-PKC schemes can be constructed by constructing
several certificateless public key encryption schemes and
modifying other existing ID based schemes. The lack of
certificates and the desire to prove the schemes secure in the
presence of an adversary who has access to the master key or has
the ability to replace public keys, requires the careful
development of new security models. We prove that some of our
schemes are secure, provided that the Bilinear Diffie-Hellman
Problem is hard.
We then examine Joux’s protocol, which is a one round, tripartite
key agreement protocol that is more bandwidth-efficient than any
previous three-party key agreement protocol, however, Joux’s protocol
is insecure, suffering from a simple man-in-the-middle attack. We
show how to make Joux’s protocol secure, presenting several tripartite,
authenticated key agreement protocols that still require only one round
of communication. The security properties of the new protocols are
studied. Applications for the protocols are also discussed
Pairing-based cryptosystems and key agreement protocols
For a long time, pairings on elliptic curves have been considered to be destructive in elliptic curve cryptography. Only recently after some pioneering works, particularly the well-known Boneh-Franklin identity-based encryption (IBE), pairings have quickly become an important tool to construct novel cryptographic schemes. In this thesis, several new cryptographic schemes with pairings are proposed, which are both efficient and secure with respect to a properly defined security model, and some relevant previous schemes are revisited. IBE provides a public key encryption mechanism where a public key can be an arbitrary string such as an entity identifier and unwieldy certificates are unnecessary. Based on the Sakai-Kasahara key construction, an IBE scheme which is secure in the Boneh-Franklin IBE model is constructed, and two identity-based key encapsulation mechanisms are proposed. These schemes achieve the best efficiency among the existing schemes to date. Recently Al-Riyami and Paterson introduced the certificateless public key encryption (CL-PKE) paradigm, which eliminates the need of certificates and at the same time retains the desirable properties of IBE without the key escrow problem. The security formulation of CL-PKE is revisited and a strong security model for this type of mechanism is defined. Following a heuristic approach, three efficient CL-PKE schemes which are secure in the defined strong security model are proposed. Identity-based two-party key agreement protocols from pairings are also investigated. The Bellare-Rogaway key agreement model is enhanced and within the model several previously unproven protocols in the literature are formally analysed. In considering that the user identity may be sensitive information in many environments, an identity-based key agreement protocol with unilateral identity privacy is proposed.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Authentication and Key Exchange in Mobile Ad Hoc Networks
Over the past decade or so, there has been rapid growth in wireless and mobile applications technologies. More recently, an
increasing emphasis has been on the potential of infrastructureless wireless mobile networks that are easy, fast and inexpensive to set up, with the view that such technologies will enable numerous new applications in a wide range of areas. Such networks are commonly referred to as mobile ad hoc networks (MANETs). Exchanging sensitive information over unprotected
wireless links with unidentified and untrusted endpoints demand the deployment of security in MANETs. However, lack of infrastructure, mobility and resource constraints of devices, wireless communication links and other unique features of MANETs induce new challenges that make implementing security a very
difficult task and require the design of specialized solutions.
This thesis is concerned with the design and analysis of security solutions for MANETs. We identify the initial exchange of authentication and key credentials, referred to as pre-authentication, as well as authentication and key exchange as primary security goals. In particular, the problem of pre-authentication has been widely neglected in existing security solutions, even though it is a necessary prerequisite for other security goals. We are the first to classify and analyze different methods of achieving pairwise pre-authentication in MANETs. Out of this investigation, we identify identity-based cryptographic (IBC) schemes as well-suited to secure MANET applications that have no sufficient security solutions at this time.
We use pairing-based IBC schemes to design an authentication and key exchange framework that meets the special requirements of MANETs. Our solutions are comprised of algorithms that allow for efficient and secure system set up, pre-authentication, mutual authentication, key establishment, key renewal, key revocation and key escrow prevention. In particular, we present the first fully self-organized key revocation scheme for MANETs that does not require any trusted third party in the network. Our revocation scheme can be used to amend existing IBC solutions, be seamlessly integrated in our security framework and even be adopted to conventional public key solutions for MANETs. Our scheme is based on propagated accusations and once the number of received accusations against a node reaches a defined threshold, the keys of the accused nodes are revoked. All communications are cryptographically protected, but unlike other proposed schemes, do not require computationally demanding digital signatures. Our scheme is the first that efficiently and securely enables nodes to revoke their own keys. Additionally, newly joining nodes can obtain previous accusations without performing computationally demanding operations such as verifying digital signatures. Several security and performance parameters make our scheme adjustable to the hostility of the MANET environment and the degree of resource
constraints of network and devices. In our security analysis we show how security parameters can be selected to prevent attacks by colluding nodes and roaming adversaries.
In our proposed security framework, we utilize special properties of pairing-based keys to design an efficient and secure method for pairwise pre-authentication and a set of ID-based authenticated key exchange protocols. In addition, we present a format for ID-based public keys that, unlike other proposed formats, allows key renewal before the start of a new expiry interval. Finally, we are the first to discuss the inherent key escrow property of IBC schemes in the context of MANETs. Our analysis shows that some special features of MANETs significantly limit the escrow capabilities of key generation centers (KGCs). We propose a novel concept of spy nodes that can be utilized by KGCs to increase their escrow capabilities and analyze the probabilities of successful escrow attacks with and without spy nodes.
In summary, we present a complete authentication and key exchange framework that is tailored for MANET applications that have previously lacked such security solutions. Our solutions can be implemented using any pairing-based IBC scheme. The component design allows for the implementation of single schemes to amend existing solutions that do not provide certain functionalities. The introduction of several security and performance parameters make our solutions adjustable to different levels of resource constraints and security needs. In addition, we present extensions
that make our solutions suitable for applications with sporadic infrastructure access as envisioned in the near future
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A novel authentication protocol based on biometric and identity-based cryptography
Recently, considerable attention has been devoted to distributed systems. It has become obvious that a high security level should be a fundamental prerequisite for organisations' processes, both in the commercial and public sectors. A crucial foundation for securing a network is the ability to reliably authenticate ommunication parties. However, these systems face some critical security risks and challenges when they attempt to stabilise between security, efficiency and functionality. Developing a secure authentication protocol can be challenging; this thesis proposes an authentication scheme that employs two authentication factors involving something you know (password) and something you are (biometric) based on Identity-Based Cryptography and Elliptic Curve Cryptography. Two protocols have been chosen that provide mutual authentication and secure key exchange, which are the equivalent to the Diffie-Hellman key exchange. Due to a potential flaw in the protocols, guarding against attacks can be challenging. In order to alleviate some of the issues encountered with the new protocol, this thesis uses the encrypt-then-authenticate method. Formal verification methods are used to evaluate the new protocol. First, finite-state machines are used to examine and predict the behaviour of the protocol. Modelling with this method shows that the new protocol can function correctly and behave correctly within the protocol description, even with invalid input or time delay. Second, Petri nets are used to model, simulate and analyse the new protocol. This thesis formulates several attack models via Petri nets in which the security of the proposed protocols is discussed precisely. Ultimately, this novel work ensures that the new protocol provides a coherent security concept and can be implemented over insecure channels while offering secure mutual authentication