Practical Certificateless Aggregate Signatures From Bilinear Maps

Aggregate signature is a digital signature with a striking property that anyone can aggregate n individual signatures on n different messages which are signed by n distinct signers, into a single compact signature to reduce computational and storage costs. In this work, two practical certificateless aggregate signature schemes are proposed from bilinear maps. The first scheme CAS-1 reduces the costs of communication and signer-side computation but trades off the storage, while CAS-2 minimizes the storage but sacrifices the communication costs. One can choose either of the schemes by consideration of the application requirement. Compare with ID-based schemes, our schemes do not entail public key certificates as well and achieve the trust level 3, which imply the frauds of the authority are detectable. Both of the schemes are proven secure in the random oracle model by assuming the intractability of the computational Diffie-Hellman problem over the groups with bilinear maps, where the forking lemma technique is avoided

Certificateless Signature Scheme Based on Rabin Algorithm and Discrete Logarithm

Certificateless signature can effectively immue the key escrow problem in the identity-based signature scheme. But the security of the most certificateless signatures usually depends on only one mathematical hard problem, which makes the signature vulnerable when the underlying hard problem has been broken. In order to strengthen the security, in this paper, a certificateless signature whose security depends on two mathematical hard problems, discrete logarithm and factoring problems, is proposed. Then, the proposed certificateless signature can be proved secure in the random oracle, and only both of the two mathematical hard problems are solved, can the proposed signature be broken. As a consequence, the proposed certificateless signature is more secure than the previous signatures. On the other hand, with the pre-computation of the exponential modular computation, it will save more time in the signature signing phase. And compared with the other schemes of this kind, the proposed scheme is more efficient

Deep Attacks of a Certificateless Signature Scheme

Certificateless public key cryptography is an attractive paradigm since it eliminates the use of certificates in traditional public key cryptography and alleviates the inherent key escrow problem in identity-based cryptography. Recently, Xiong et al. proposed a certificateless signature scheme and proved that their scheme is existentially unforgeable against adaptive chosen message attack under the random oracle model. He et al. pointed out that Xiong et al.’s scheme is insecure against the Type II adversary. But, their forged signatures are not random, and their improved scheme has the same security defects as Xiong et al.’s scheme. In this paper, we present two malicious-but-passive KGC attack methods on Xiong et al.’s scheme and our results show that their scheme is insecure against malicious-but-passive KGC attack

Flaw and Improvement of Three Certificateless Signature Schemes

对最近提出的2个在随机预言模型中可证安全的无证书签名方案和1个在标准模型中可证安全的无证书签名方案进行安全性分析,指出这3个方案不能抵抗替换公钥攻击的安全隐患,在这种攻击下攻击者能够生成新的公钥满足合法签名者生成的合法签名。给出改进措施,有效克服原方案中的设计缺陷。The security flaws of two provably-secure certificateless signature schemes in the random oracle model and a provably-secure certificateless signature scheme in the standard model are analyzed.It is found that the three schemes are all insecure against public key replacement attack.In this attack,an adversary can generate a new public key satisfying legitimate signatures created by the legitimate signer.In order to avoid these flaws,an improvement measure is proposed,which can resolve the security problems existing in the original schemes.国家自然科学基金资助项目(60704042);国家“十一五”科技支撑计划基金资助项目(2007BAK34B04);福建省教育厅科技基金资助项目(JA08156);福建省青年科技人才创新基金资助项目(2008F3110

A Certificate-Based Proxy Signature with Message Recovery without Bilinear Pairing

In this paper, we propose the first provable secure certificate-based proxy signature with message recovery without bilinear pairing. The notion of certificate-based cryptography was initially introduced by Gentry in 2003, in order to simplify certificate management in traditional public key cryptography(PKC)and to solve the key escrow problem in identity-based cryptosystems. To date, a number of certificate-based proxy signature(CBPS)schemes from bilinear pairing have been proposed. Nonetheless, the total computation cost of a pairing is higher than that of scalar multiplication(e.g., over elliptic curve group). Consequently, schemes without pairings would be more appealing in terms of efficiency. According to the available research in this regard, our scheme is the first provable secure CBPS scheme with message recovery which is based on the elliptic curve discrete logarithm problem. We prove the security of the presented scheme against existential forgery under adaptive chosen message and ID attacks in the random oracle model. Moreover, the paper will also show how it would be possible to convert this scheme to the CBPS scheme without message recovery. This scheme has more applications in situations with limited bandwidth and power-constrained devices

Certificateless Proxy Signature from RSA

Although some good results were achieved in speeding up the computation of pairing function in recent years, it is still interesting to design efficient cryptosystems with less bilinear pairing operation. A proxy signature scheme allows a proxy signer to sign messages on behalf of an original signer within a given context. We propose a certificateless proxy signature (CLPS) scheme from RSA and prove its security under the strongest security model where the Type I/II adversary is a super Type I/II adversary

McCLS: Certificateless Signature Scheme for Emergency Mobile Wireless Cyber-Physical Systems

Mobile Ad Hoc Network is a self-configurable and self-organizing wireless network of mobile devices without fixed infrastructure support, which makes it a good candidate as underlying communication network for the Cyber-Physical Systems in emergency conditions such as earthquake, flood, and battlefields. In these scenarios, efficient communication schemes with security support are especially desired. Two cryptography approaches, the public key cryptography and the identitybased cryptography, face the costly and complex key management problem and the “key escrow" problem in the real-life deployment. Recently, the certificateless public key cryptography (CL-PKC) was introduced to address these problems in previous approaches. However, the efficiency of the schemes based on CL-PKC is not high and can be improved further. In this paper, we present an improved certificateless signature scheme (McCLS) based on bilinear pairings. First, we theoretically compare the efficiency of McCLS with that of existing certificateless signature schemes (CLS). Second, an empirical study is conducted to compare the traditional AODV with the McCLS scheme based on AODV (McDV) in their efficiency and effectiveness against two most common attacks (i.e. redirection attack and rushing attack). Results from theoretical analysis show that the new McCLS scheme is more efficient than existing CLS solutions, and results from empirical studies show that the McDV is able to resist the two common attacks without causing substantial degradation of the network performance

The Role of the Adversary Model in Applied Security Research

Adversary models have been integral to the design of provably-secure cryptographic schemes or protocols. However, their use in other computer science research disciplines is relatively limited, particularly in the case of applied security research (e.g., mobile app and vulnerability studies). In this study, we conduct a survey of prominent adversary models used in the seminal field of cryptography, and more recent mobile and Internet of Things (IoT) research. Motivated by the findings from the cryptography survey, we propose a classification scheme for common app-based adversaries used in mobile security research, and classify key papers using the proposed scheme. Finally, we discuss recent work involving adversary models in the contemporary research field of IoT. We contribute recommendations to aid researchers working in applied (IoT) security based upon our findings from the mobile and cryptography literature. The key recommendation is for authors to clearly define adversary goals, assumptions and capabilities

Managing and Complementing Public Key Infrastructure for Securing Vehicular Ad Hoc Networks

Recently, vehicular ad-hoc network (VANET) has emerged as an excellent candidate to change the life style of the traveling passengers along the roads and highways in terms of improving the safety levels and providing a wide range of comfort applications. Due to the foreseen impact of VANETs on our lives, extensive attentions in industry and academia are directed towards bringing VANETs into real life and standardizing its network operation. Unfortunately, the open medium nature of wireless communications and the high-speed mobility of a large number of vehicles in VANETs pose many challenges that should be solved before deploying VANETs. It is evident that any malicious behavior of a user, such as injecting false information, modifying and replaying the disseminated messages, could be fatal to other legal users. In addition, users show prime interest in protecting their privacy. The privacy of users must be guaranteed in the sense that the privacy-related information of a vehicle should be protected to prevent an observer from revealing the real identities of the users, tracking their locations, and inferring sensitive data. From the aforementioned discussion, it is clear that security and privacy preservation are among the critical challenges for the deployment of VANETs. Public Key Infrastructure (PKI) is a well-recognized solution to secure VANETs. However, the traditional management of PKI cannot meet the security requirements of VANETs. In addition, some security services such as location privacy and fast authentication cannot be provided by the traditional PKI. Consequently, to satisfy the security and privacy requirements, it is prerequisite to elaborately design an efficient management of PKI and complementary mechanisms for PKI to achieve security and privacy preservation for practical VANETs. In this thesis, we focus on developing an efficient certificate management in PKI and designing PKI complementary mechanisms to provide security and privacy for VANETs. The accomplishments of this thesis can be briefly summarized as follows. Firstly, we propose an efficient Distributed Certificate Service (DCS) scheme for vehicular networks. The proposed scheme offers a flexible interoperability for certificate service in heterogeneous administrative authorities, and an efficient way for any On-Board Units (OBUs) to update its certificate from the available infrastructure Road-Side Units (RSUs) in a timely manner. In addition, the DCS scheme introduces an aggregate batch verification technique for authenticating certificate-based signatures, which significantly decreases the verification overhead. Secondly, we propose an Efficient Decentralized Revocation (EDR) protocol based on a novel pairing-based threshold scheme and a probabilistic key distribution technique. Because of the decentralized nature of the EDR protocol, it enables a group of legitimate vehicles to perform fast revocation of a nearby misbehaving vehicle. Consequently, the EDR protocol improves the safety levels in VANETs as it diminishes the revocation vulnerability window existing in the conventional Certificate Revocation Lists (CRLs). Finally, we propose complementing PKI with group communication to achieve location privacy and expedite message authentication. In specific, the proposed complemented PKI features the following. First, it employs a probabilistic key distribution to establish a shared secret group key between non-revoked OBUs. Second, it uses the shared secret group key to perform expedite message authentication (EMAP) which replaces the time-consuming CRL checking process by an efficient revocation checking process. Third, it uses the shared secret group key to provide novel location privacy preservation through random encryption periods (REP) which ensures that the requirements to track a vehicle are always violated. Moreover, in case of revocation an OBU can calculate the new group key and update its compromised keys even if the OBU missed previous rekeying process. For each of the aforementioned accomplishments, we conduct security analysis and performance evaluation to demonstrate the reliable security and efficiency of the proposed schemes