Certificateless cryptography involves a Key Generation Center (KGC) which issues a partial key to a user and the user also independently generates an additional public/secret key pair in such a way that the KGC who knows only the partial key but not the additional secret key is not able to do any cryptographic operation on behalf of the user; and a third party who replaces the public/secret key pair but does not know the partial key cannot do any cryptographic operation as the user either. We call this attack launched by the third party as the key replacement attack. In ACISP 2004, Yum and Lee proposed a generic construction of digital signature schemes under the framework of certificateless cryptography. In this paper, we show that their generic construction is insecure against key replacement attack. In particular, we show that the security requirements of their generic building blocks are insufficient to support some security claim stated in their paper. We then propose a modification of their scheme and show its security in a new and simplified security model. We show that our simplified definition and adversarial model not only capture all the distinct features of certificateless signature but are also more versatile when compared with all the comparable ones. We believe that the model itself is of independent interest.

Key replacement attack against a generic construction of certificateless signature

Researchers are particularly interested in factors that affect the adoption, innovations and diffusion of mobile payment, which is a typical and wide application of ICTS (Information Communication Technology Services) in developed and developing countries. Though mobile payment is an exciting domain and rapidly evolved in recent years, the existence of standardized, interconnected and widely-accepted mobile payment procedures is crucial for successful diffusion of mobile payment and has mobile commerce globally, even in one country or region. In this paper we make a comparison of mobile payment procedures in the Finnish and the Chinese market. Current payment procedures can be categorized by using strategic, participatory and operational criteria, according to the morphological method. Based on these, we analyze the current contraints on the mobile payment procedures in the Finnish-Chinese market in order to make it clear whether we can develop a generally accepted mobile payment integrative solution or merge different procedures into an interoperability system via interconnected participants with high-level protocols and regulation when necessary, because

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A Comparison of Mobile Payment Procedures in Finnish and Chinese Markets

Since public key cryptography is usually build using computationally expensive operation, it has been out of reach for resource constrained and low power devices. Today there are a large number of low power devices in use and they perform complex tasks. There is need for light weight cryptography having high security and low communication overhead. Online/Offline schemes are well suited for this purpose since they allow the use of public key cryptosystems in these low power devices. Many cryptosystems that are efficient in terms of number of computational steps may be inefficient if we consider the size of keys that must be used to achieve a acceptable level of security. Especially cryptosystems that have a loose security proof may work with large keys, this increases the communication overhead. In this paper, we show a view of the how Certificateless schemes are constructed. Then, we present a Certificateless Online/Offline Signature (CLOOS) Scheme and give a tight security reduction to the Gap Diffie-Hellman problem in the random oracle model. Even though other schemes exist that are are constructed using less number computational steps, if we take into account the size of keys our scheme will be more efficient. Thus, our scheme is light weight and has a low communication overhead.

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Efficient Certificateless Online/Offline Signature with tight security

Public key cryptography usually is computationally more expensive than symmetric key systems. Due to this low power or resource constrained devices cannot make use of public key cryptosystems easily. There is a need for high security in these devices since many of these devices perform complex tasks which includes interaction with third party cloud infrastructures. These cloud infrastructures are not trusted entities. Hence there is need for light weight public key cryptography which are secure against these cloud administrators. The trusted entity in certificateless schemes cannot compromise the security of the users. Online/offline have two parts, first the computationally heavy part(offline) of the cryptosystem and then the main “online” algorithm for use on resource constrained devices. The heavy computations are done in the offline phase on a more powerful device. Hence, Certificateless online/offline schemes are perfect for low power devices interacting with clouds. In this paper, we present a certificateless online/offline signature scheme. This scheme is the most efficient certificateless signature scheme in existence and also has the added advantage of being online/offline. The scheme is proven secure in the random oracle model.

Efficient Certificateless Online/Offline Signature.

Aiming at the problems of implementing the conventional IKE authentications such as pre-shared key and certificate-based Public Key Infrastructure (PKI), this paper proposes a new certificateless IKE authentication scheme. This scheme uses bilinear pairing to structure the framework of certificateless IKE authentication, solves the end to end IPSec security by removing the requirement of both nodes either to be manually configured with the common shared key or to exchange the certificates and the necessity to be enrolled to certain Certificate Authority (CA). Furthermore, this paper provides a set of specifications for implementing IKE authentication using certificateless signature that can be used to verify the validity of the scheme in a single trust domain infrastructure.

IKE authentication using certificateless signature

In Asiacrypt'03, Al-Riyami and Paterson introduced the concept of certificateless public key cryptography (CLPKC). CLPKC is a paradigm to solve the inherent key escrow problem suffered by identity-based cryptography (IBC). In this paper, we propose a practical certificateless signature (CLS) scheme based on bilinear pairings. Three pairing computations can be used in the verification algo- rithm of our scheme, in contrast to at least four pairing in the verification phase of previous provably secure CLS schemes. In addition, only one pairing which is precom- putable can be saved in the sign algorithm. The security of the proposed scheme can be proved to be equivalent to the Inverse Computational Diffie-Hellman problem and q- Strong Diffie-Hellman problem in the random oracle model.

A Practical Certificateless Signature Scheme

To date, most of the constructions of provably secure identity based signature (IBS) scheme are based on the approach of attaching certificates to non-identity based signatures in the random oracle In ACISP'06, Paterson et al proposed the first direct construction of IBS in the standard model However, Paterson et al's scheme has a large size of the public parameter, which is not suitable for environments with limited storage capacity In this paper, we proposed an efficient provably secure IBS scheme in the standard model based on bilinear pairings To the best of our knowledge, our scheme is another direct construction and more efficient by reducing about half the size of public parameters than Paterson et al's scheme Assuming the intractability of the Computational Diffie-Hellman problem, our IBS scheme is unforgeable under an adaptive chosen-message attack without resorting to random oracle

Lifeng Guo

Papers

A Practical Certificateless Signature Scheme

Practical identity-based signature without random oracle