Qiuliang Xu

A Two-party certificateless authenticated key agreement protocol without pairing

Authenticated key agreement (AK) protocol is crucial in providing data confidentiality and integrity for subsequent communications among two or more parties over a public network. Certificateless public key cryptography (CL-PKC) combines the advantage of the identity-based public key cryptography (ID-PKC) and the traditional public key cryptography (PKC). Unfortunately, construction of CL-PKC and AK protocols has so far depended on the use of identity-based encryption, which results in the bilinear pairing-based schemes that need costly operations. We present a secure certificateless authenticated key agreement protocol without paring, based on the certificateless encryption scheme proposed by J. Baek et al. It shows that the newly proposed scheme is of nice efficiency and practical. Moreover, it provides perfect forward secrecy, PKG forward secrecy and almost all the other known security attributes, such as known-key secrecy, key-compromise impersonation resilience, unknown key-share resilience, known session-specific temporary information security, message independence and no key control.

Attribute-based re-encryption scheme in the standard model

In this paper, we propose a new attribute-based proxy re-encryption scheme, where a semi-trusted proxy, with some additional information, can transform a ciphertext under a set of attributes into a new ciphertext under another set of attributes on the same message, but not vice versa, furthermore, its security was proved in the standard model based on decisional bilinear Diffie-Hellman assumption. This scheme can be used to realize fine-grained selectively sharing of encrypted data, but the general proxy re-encryption scheme severely can not do it, so the proposed scheme can be thought as an improvement of general traditional proxy re-encryption scheme.

Social rational secure multi-party computation

Rational party is a new kind of parties who behave neither like honest parties nor like malicious adversaries. The crux point of rational party is the definition of the utility function, as rational parties only care about how to maximize their utility. In other words, rational parties choose the strategies, which can bring them the highest utilities. In rational secure two‐party computation protocol, the main task is how to boost mutual cooperation to complete the protocol. Social rational secure multi‐party computation (SRSMPC) means that in a social network, some distributed and rational parties with reputation properties want to jointly compute a functionality. The seemingly simple task becomes tough under three conditions. The first condition is that the network composed by parties may not be complete. That is, two parties may not be neighbors and they are connected through other parties. The second is that the network may be not secure. That is, messages may be tempered by malicious parties. The third condition is that parties may run the protocol under incomplete information scenario. That is, parties may have types and each type has a corresponding utility function. Under the first and second conditions, parties need to consider how to securely transmit messages between two parties who are not neighbors. Under the third condition, we propose the Tit‐for‐Tat strategy and prove that mutual cooperation is a sequential equilibrium between two parties. In this paper, we construct an SRSMPC protocol by using mechanism design under incomplete information to facilitate the implementation of the SRSMPC protocol within constant rounds. Meanwhile, newcomers are allowed to participate in the protocol. To the best of our knowledge, this is the first social rational secure computation protocol for multi‐party under an incomplete information scenario and an incomplete network. Copyright

New rational parties relying on reputation

In this paper, we redefine the utilities considering other parts such as reputation in order to give rational parties incentives to participate in the protocol and finally get the correct outputs. The most distinct contribution of this paper is the proposal of rational covert adversaries whose behaviors are combinations of rational parties and covert adversaries. Finally, given proper parameters, we prove that all parties have incentives to participate in the rational secure computation protocol. Copyright

Fair two-party computation with rational parties holding private types

Rational secure two-party computation RSTPC applies game theory to cryptographic protocols, where rational parties only care about how to maximize their utilities. Fairness can be achieved by assuming rational behavior in RSTPC. Previous RSTPC protocols achieve fairness under symmetric information, which seems quite strong and unnatural for rational parties. In this paper, we consider a general RSTPC protocol under asymmetric information where previous equilibriums are inadequate to guarantee fairness. Therefore, we propose a stronger equilibrium named computationally sequential equilibrium to guarantee fairness under asymmetric information. Furthermore, our protocol only requires small constant communication rounds. Copyright

Key Replicating Attack on Certificateless Authenticated Key Agreement Protocol

Authenticated key agreement protocol is crucial in providing data confidentiality and integrity to subsequent communications among two or more parties over a public network. Certificateless public key cryptography (CL-PKC) combines the advantage of the identity-based public key cryptography (ID-PKC) and the traditional PKI. In 2007, Y.J Shi and J.H Li proposed a two-party authenticated key agreement protocol based on the certificateless encryption scheme proposed by B. Libert and J.J. Quisquater. It is found that the scheme is vulnerable to the key replicating attack (one form of the man-in-the-middle attack), so it doesn’t possess the security attribute of implicit key authentication and key control. We analyze such an attack of this protocol in the BR93 model in detail, and demonstrate that the protocol is not secure if the adversary is allowed to send a reveal query to reveal non-partner players who had accepted the same session key.

Constructing Secure Two-Party Authenticated Key Agreement Protocol Based on Certificateless Public Key Encryption Scheme

Authenticated key agreement protocol is one of the important cryptographic primitives to ensure secure communication in an open network. Certificateless public key cryptography (CL-PKC) represents an interesting and potentially useful balance between public key cryptography based on certificates and identity-based cryptography. The topic of CL-PKC has undergone quite rapid development with schemes being proposed for encryption and signatures, while certificateless authenticated key agreement protocols are seldom discussed. In this paper, we present a secure two-party authenticated key agreement protocol based on an efficient certificateless public key encryption with pairing. Such a scheme achieves almost all of the security attributes, including known-key secrecy, perfect forward secrecy, PKG forward secrecy, key-compromise impersonation resilience, unknown key-share resilience, known session-specific temporary information security, message independence and no key control. Meanwhile, it is also practical with nice efficiency.

A brief survey on secure multi-party computing in the presence of rational parties

Intelligent agents (IA) are autonomous entities which observe through sensors and act upon an environment using actuators to adjust their activities towards achieving certain goals. The architectures of agents have enormous potentials when they are applied into critical systems, where agents choose actions between working with their own and cooperating with others. Rational utility-based agents choose actions to maximize their expected utilities. Rational secure multi-party computing (RSMPC) means secure multi-party computing (SMPC) in the presence of rational utility-based agents. Here, we call them rational parties. In this paper certain goals of rational parties are maximizing their utilities. The introduction of rational parties considers the incentives in executing protocols. The security definitions under rational framework can better demonstrate the executing environment of real protocols. Furthermore, rational two-party computing removes some impossibility in traditional two-party computing, such as fairness. This paper represents the research status of RSMPC and some typical protocols. The advantages and disadvantages of previous rational SMPC protocols are discussed here. As an emerging field, there are still lots of open problems in RSMPC, such as communication channels, utility assumptions and equilibrium notions etc.

An efficient and secure one-round authenticated key agreement protocol without pairings

Two-Party Authenticated key agreement protocol is essential for setting up the common session key for parties to establish secure channel for network communication in the open environment. Most of proposed schemes require expensive bilinear pairing operation and only provide limited security attributes. So such protocols are unsuitable for real-world applications that require stronger sense of secrecy. In this paper, we first analysis two schemes recently proposed by Cao etc., and then present a one-round ID-based authenticated key agreement protocol with more desired security attributes, which need no pairing operations while still achieve nice computational efficiency. These security attributes include known-key secrecy, perfect forward secrecy, PKG forward secrecy, key-compromise impersonation resilience, unknown key-share resilience and no key control. Moreover, it captures the enhanced security attributes - known session-specific temporary key information secrecy, which means that even the ephemeral secret key were compromised, the adversary can hardly acquire the agreed session key.

Secure Two-Party Computation in Social Cloud Based on Reputation

Parties are expected to be cooperative such that some tasks, e.g. Two-party computation in social cloud, become much easier. It is well known that reputation is an important property to promote cooperation among parties in game theory. Therefore, we consider the effect of reputation when parties interact in social cloud to find a new way realizing mutual cooperation. More specifically, parities in the social cloud are rational who value their reputation. Cooperation can boost their reputation, so they have incentives to cooperate with others such that they may get a higher utility. The basic idea of this paper is to add reputation deriving from social cloudas part of the utility. That is, we describe the architecture and interaction between two rational parties in the social cloud, where two parties receive their opponents trust or reputation from the social cloud. The computation of trust and reputation is finished in the social cloud. Finally, we prove that given proper parameters in rational secure two-party computation (rational STPC), it is possible to complete the computation in just one round in the second stage of the protocol.