Key Generation Center Attacks Research Articles

A Conditional Privacy-Preserving Certificateless Aggregate Signature Scheme in the Standard Model for VANETs

Vehicular ad hoc networks (VANETs) are the communication foundation for future intelligent transportation systems and guarantee safe driving of intelligent networked vehicles. Moreover, VANETs face a series of security challenges related to the protection of vehicle privacy, authenticity of transmitted information, and bandwidth limitations. To resolve these contradictions, many certificateless aggregate signature (CLAS) schemes have been proposed. However, the majority of them can neither resist malicious-but-passive key generation center attacks, replay attacks, and link attacks, nor track the actual identities of malicious vehicles. Meanwhile, the security of previous CLAS schemes in VANETs is only formally provided in the random oracle model (ROM), which might be insecure in actual implementation. In addition, most CLAS schemes still have problems of large verification delays and high communication overhead. To address the above-mentioned problems, a new conditional privacy-preserving CLAS scheme in VANETs is proposed, which adopts full aggregation technology to reduce computation and bandwidth resources. According to the formal security proofs under the computational Diffie-Hellman problem (CDHP) given in the standard model (SM), the security level of this scheme is higher than that of other CLAS schemes under ROM in practical applications. Additionally, the use of pseudonym mechanism realizes conditional privacy protection in VANETs. The performance analysis shows that this scheme has a higher efficiency in terms of computation and communication overhead compared with several previous CLAS schemes.

Top-Level Secure Certificateless Signature Against Malicious-But-Passive KGC

Certificateless signature (CLS) has no need of public key certificates and also avoids excessive dependence to a third party like that in identity-based setting. Recently, Shim (IEEE Systems Journal, doi:10.1109/JSYST.2018.2844809) came up with a CLS scheme independent of random oracles and asserted that the construction can be immune to the public key replacement attacks and the malicious-but-passive key generation center (KGC) attacks. In this paper, we analyze the security of Shim’s scheme and point out that his conclusions are incorrect by giving two concrete counter-examples. We repair the scheme and put forward a CLS scheme secure against public key replacement attacks and malicious-but-passive KGC attacks without relying on random oracles. Compared with Shim’s scheme, our construction has lower execution cost for signing and verification, and achieves Girault’s top-level security, which means that a victim can repudiate the forgeries based on a false secret key generated by the KGC.

Efficient and secure certificateless signature scheme in the standard model

SummaryCertificateless cryptography not only enjoys many advantages of identity‐based cryptography (IBC) but also eliminates the fatal drawback, which is called the key escrow in IBC. Most of the early certificateless signature schemes are secure based on the random oracle model, and nowadays, more and more researchers put emphasis on the scheme based on the standard model. In 2010, Xia et al. demonstrated that the previous schemes in the standard model cannot resist the public‐key‐replace attack. In 2012, for the purpose of overcoming the common drawback, Yu et al. presented a new certificateless signature scheme. However, under the public‐key‐replace attack and malicious‐but‐passive key generation center attack, this scheme is proven to be vulnerable. Moreover, there are too many bilinear pairings used in this scheme, which lead to its low computation efficiency. Aiming at the weakness of the scheme byYu et al., we propose a new certificateless signature scheme, which provides stronger security and higher computational efficiency than the existing schemes. In addition, according to the concept of Girault's trust level, the new scheme can reach trust level 3. Copyright © 2015 John Wiley & Sons, Ltd.

Strongly secure certificateless key-insulated signature secure in the standard model

To protect signing rights against the compromise of secret key, the key-insulated signature (KIS) has attracted a lot of attention from the industry and academia. It would be interesting to investigate the notion of KIS in the certificateless public key cryptography (CL-PKC) environment to solve the problem of certificate management and key escrow simultaneously. To capture the seeming neglected attack mounted by the malicious key generation center (KGC), a stronger security model for the CL-PKC should be considered. In this paper, we first show that the only known CL-KIS scheme is vulnerable against malicious KGC attack, and then propose the first CL-KIS scheme secure against malicious KGC attack, with security proof in the standard model.

A new certificateless signature scheme under enhanced security models

AbstractIn identity‐based signatures, the key generation center (KGC) always knows user private key, and thus, it can always impersonate the user. Certificateless signatures were introduced by Al‐Riyami and Paterson to solve this key escrow problem of identity‐based signatures in 2003. In certificateless signatures, the private key is determined by neither the user nor the KGC. In 2007, Huang et al. revisited the security models of certificateless signatures. They divided potential adversaries according to their attack power into normal, strong and super adversaries. On the other hand, Au et al. introduced a new attack called malicious‐but‐passive KGC attack in the same year. In the new attack, KGC that holds the master secret key is assumed malicious at the very beginning of the setup phase of the system. The previous schemes that can be proven secure against malicious‐but‐passive KGC attack provided only the security against strong adversaries. In this paper, we construct the first certificateless signature scheme that can be proven secure against malicious‐but‐passive KGC attack of super adversaries. Moreover, our scheme is still secure when the adversary is allowed to obtain valid signatures on the target identity and message. Our construction is based on the hard lattice problems in the random oracle model.Copyright © 2014 John Wiley & Sons, Ltd.

Cryptanalysis and improvement of a certificateless encryption scheme in the standard model

Certificateless public key cryptography eliminates inherent key escrow problem in identity-based cryptography, and does not yet requires certificates as in the traditional public key infrastructure. In this paper, we give crypt-analysis to Hwang et al.'s certificateless encryption scheme which is the first concrete certificateless encryption scheme that can be proved to be secure against "malicious-but-passive" key generation center (KGC) attack in the standard model. Their scheme is proved to be insecure even in a weaker security model called "honest-but-curious" KGC attack model. We then propose an improved scheme which is really secure against "malicious-but-passive" KGC attack in the standard model.

Security analysis and improvement of certificateless signature scheme without bilinear pairing

By analyzing the security of a certificateless signature scheme without bilinear pairing proposed by Wang Shengbao,et al.(WANG S B,LIU W H,XIE Q.Certificateless signature scheme without bilinear pairings.Journal on Communications,2012,33(4) : 93-98),it indicated that the scheme could not resist malicious attack of positive dishonest Key Generation Center(KGC).For this kind of attack,detailed attack method was given,and an improved scheme was proposed.Finally,the security of the improved scheme was analyzed.The result shows that the proved scheme can resist the malicious KGC attack,maintain efficiency of the original scheme and has higher security.Meanwhile,the communication complexity is reduced due to the elimination of the security channel.

Efficient certificateless encryption withstanding attacks from malicious KGC without using random oracles

ABSTRACTAs the key generation center (KGC) in a certificateless cryptosystem is no longer fully trusted, for practical applications, a secure certificateless encryption (CLE) scheme should withstand malicious KGC attacks. In this paper, we investigate practical CLE schemes withstanding attacks from a malicious KGC without resorting to random oracles. At first, we show the insecurity of the CLE scheme (ZW scheme) presented by Zhang and Wang. Although ZW scheme was proved to be chosen ciphertext secure without using random oracles, we find that it cannot resist attacks from a malicious KGC. We show an attack that demonstrates a malicious KGC can easily decrypt a target ciphertext using chosen ciphertext attack. After that, we introduce a new efficient CLE scheme. We prove its CCA2 security without using random oracles. Our new scheme not only gets rid of the security drawbacks of ZW scheme but also keeps its most distinctive feature of a short public key length. The formal security proofs of the new scheme are presented without using random oracles assuming the hardness of the decisional truncated q‐augmented bilinear Diffie‐Hellman exponent (q‐ABDHE) problem and the hardness of the decisional bilinear Diffie–Hellman problem. Copyright © 2013 John Wiley & Sons, Ltd.

Cryptanalysis and improvement of a certificateless threshold signature secure in the standard model

In this paper, we focus on security analysis of certificateless signature (CLS) schemes and certificateless threshold signature (CLTHS) schemes. We first propose four common attack methods for analyzing security of CLS schemes and CLTHS schemes. Then we give seven existing schemes as examples for demonstrating how to use our common attack methods, and prove that these schemes are vulnerable against public key replacement attacks or malicious-but-passive key generation center (KGC) attacks. By comprehensively using the proposed attack ideas, we also present three attacks against a CLTHS scheme proposed by Xiong et al. (2010) [28]: two public key replacement attacks and a malicious-but-passive KGC attack. Furthermore, we point out the flaws in the security proofs of these insecure CLS or CLTHS schemes. Finally, to resist these attacks, we propose an improved CLTHS scheme.

Generic certificateless encryption secure against malicious-hut-passive KGC attacks in the standard model

Despite the large number of certificateless encryption schemes proposed recently, many of them have been found insecure under a practical attack, called malicious-but-passive KGC (Key Generation Center) attack. In this work we propose the first generic construction of certificateless encryption, which can be proven secure against malicious-but-passive KGC attacks in the standard model. In order to encrypt a message of any length, we consider the KEM/DEM (key encapsulation mechanism/data encapsulation mechanism) framework in the certificateless setting, and propose a generic construction of certificateless key encapsulation mechanism (CL-KEM) secure against malicious-but-passive KGC attacks in the standard model. It is based on an identity-based KEM, a public key encryption and a message authentication code. The high efficiency of our construction is due to the efficient implementations of these underlying building blocks, and is comparable to Bentahar et al.'s CL-KEMs, which have only been proven secure under the random oracle model with no consideration of the malicious-but-passive KGC attack. We also introduce the notion of certificateless tag-based KEM (CL-TKEM), which is an extension of Abe et al.'s work to the certificateless setting. We show that an efficient CL-TKEM can be constructed by modifying our CL-KEM scheme. We also show that with a CL-TKEM and a data encapsulation mechanism secure under our proposed security model, an efficient certificateless hybrid encryption can be constructed by applying Abe et al. 's transformation in the certificateless setting.

Certificateless signcryption scheme in the standard model

Certificateless public key signcryption scheme is an important cryptographic primitive in cryptography. Barbosa and Farshim proposed a certificateless signcryption scheme. However, their construction is proven to be secure in the random oracle model but not the standard model, and the scheme is also vunlerable to the malicious-but-passive key generation center (KGC) attacks. To overcome these disadvantages, we introduce a formal security model for certificateless signcryption schemes secure against the malicious-but-passive KGC attacks and propose a novel certificateless signcryption scheme. The proposed certificateless signcryption scheme is proven to be IND-CCA2 secure under the decisional Bilinear Diffie–Hellman intractability assumption without using the random oracles. The proposed scheme is also proven to be existentially unforgeable under the computational Diffie–Hellman intractability assumptions. Furthermore, performance analysis shows that the proposed scheme is efficient and practical.

Certificateless Public Key Encryption Secure against Malicious KGC Attacks in the Standard Model

Recently, Au et al. (Au et al. 2007) pointed out a seemingly neglected se- curity concern for certificateless public key encryption (CL-PKE) scheme, where a malicious key generation center (KGC) can compromise the confidentiality of the mes- sages by embedding extra trapdoors in the system parameter. Although some schemes are secure against such an attack, they require random oracles to prove the security. In this paper, we first show that two existing CL-PKE schemes without random ora- cles are not secure against malicious KGC, we then propose the first CL-PKE scheme secure against malicious KGC attack, with proof in the standard model.