In the universal composability framework we consider ideal functionalities for secure messaging and signcryption. Using traditional formal methods techniques we show that the secure messaging functionality can be UC-realized by a hybrid protocol that uses the signcryption functionality and a public key infrastructure functionality. We also discuss that the signcryption functionality can be UC-r...

An online/offline signcryption scheme provides confidentiality and authentication simultaneously, and it is particularly suitable for the application of resource-constrained systems. In this paper, we present a key-exposure free online/offline signcryption scheme. In contrast, it seems that all the existing online/offline signcryption schemes based on Shamir-Tauman’s paradigm suffer from the ke...

Signcryption can realize the function of encryption and signature in a reasonable logic step, which can lower computational costs and communication overheads. In 2008, S. S. D. Selvi et al. proposed an identitybased threshold signcryption scheme. In this paper, we show that the threshold signcryption scheme of S. S. D. Selvi et al. is vulnerable if the attacker can replaces the group public key...

Public key cryptography has found many applications in our modern society. To guarantee the authenticity of public keys, we need a trusted third party (TTP). In 1991, Girault defined three trust levels for a TTP. The higher the trusted level of the TTP is, the higher the security level of the cryptographic scheme is. In 2007, Hu et al. proposed a generic construction of a certificateless signat...

Signcryption is a new public key cryptography approach to combine digital signature and encryption functionalities as a consequence of the growing consumer demand for information security. The necessity to achieve confidentiality, integrity, authenticity and non-repudiation properties in data communication that motivates new demands for signcryption schemes. The framework of signcryption involv...

As people in modern societies are busier than any human era and computer network has profound impact on how people work and live through fast and convenient information exchange, people need more help from each other to accomplish more work via network connections in limited period of time. Therefore, privilege delegation mechanism has become a necessary service in modern enterprises and organi...

Signcryption is a new cryptographic primitive that performs signing and encryption simultaneously, at a cost significantly lower than that required by the traditional signature-then-encryption approach. In this paper, we present a security analysis of two such schemes: the HuangChang convertible signcryption scheme [12], and the Kwak-Moon group signcryption scheme [13]. Our results show that bo...

Despite the fact that the traditional public key infrastructure provides Level 3 trusted authority, but its two major problems of scalability and certificate management raised the need to an alternative security infrastructure. That motivated the appearance of new technologies to replace the traditional PKI, such as the Identity based encryption, the certificateless encryption, etc. But all tho...

Certificateless signature scheme is a practical solution to confront the drawback, Key Generation Center (KGC) being able to forge the signature of a user, of an identity based (ID-based) signature scheme. Lots of previous research results have shown the security models and the generic constructions for certificateless signatures. However, most of them did not satisfy Girault’s level-3 security...

With the development of the wireless communication technology and the sensor technology, the wireless sensor network (WSN) has been used in many applications. However, WSNs suffer from some inherent weaknesses because of restricted communication and hardware capabilities. To achieve essentially secure communication in WSNs, a few of key management models have been proposed since it is the cruci...