The fair problem of secure multiparty computation protocol was investigated in the universally composable framework. A fair secure multiparty computation model with ideal functionalities was firstly formulated such as a fair secure multiparty addition computation and a fair secure multiparty multiplicative computation. Next a fair addition computation protocol and a fair multiplicative computation protocol based on the bilinear paring and the ideal functionality of a commitment scheme was proposed. The proposed protocols can securely realize their ideal functionalities in the hybrid model respectively. Finally, analysis show that these schemes are effective, and it can be more applicable in special situation.
The fair problem of secure multiparty computation protocol was investigated in the universally composable framework. A fair secure multiparty computation model with ideal functionalities was firstly formulated such as a fair secure multiparty addition computation and a fair secure multiparty multiplicative computation. Next a fair addition computation protocol and a fair multiplicative computation protocol based on the bilinear paring and the ideal functionality of a commitment scheme was proposed. The proposed protocols can securely realize their ideal functionalities in the hybrid model respectively. Finally, analysis show that these schemes are effective, and it can be more applicable in special situation.
We consider the problem of constructing secure multi-party computation (MPC) protocols that are completely fair — meaning that either all the parties learn the output of the function, or nobody does — even when a majority of the parties are corrupted. We first propose a framework for fair multi-party computation (FMPC), within which we formulate a definition of secure and fair protocols. The definition follows the standard simulation paradigm, but is modified to allow the protocol to depend on the runing time of the adversary. In this way, we avoid a well-known impossibility result for fair MPC with corrupted majority; in particular, our definition admits constructions that tolerate up to (n− 1) corruptions, where n is the total number of parties. Next, we define a “commit-prove-fair-open” functionality and construct an efficient protocol that realizes it, using a new variant of a cryptographic primitive known as “time-lines.” With this functionality, we show that some of the existing secure MPC protocols can be easily transformed into fair protocols while preserving their security. Furthermore, these protocols remain secure when arbitrarily composed with any protocols, which means, in particular, that they are concurrently composable and non-malleable. This is joint work with Phil MacKenzie and Ke Yang.
At present,most group signature is only secure in the standard alone.Its security becomes weak in multiple protocol environment.In view of this,the security of group signature protocol is studied in the multiple concurrent execution under the universally composable framework.Since the protocol can be analyzed modularly under the universally composable framework,an ideal function of group signature protocol is defined in this framework.Then a group signature protocol is proposed to realize the ideal function,and its universally composable security as well as unforgeability is also proved.Furthermore,a concrete instance of this universally composable group signature protocol is given.Analysis results show that this protocol security is suitable for applications in multiple concurrent environment.
Abstract We study the problem of constructing secure multi-party computation (MPC) protocols thatare completely fair-- meaning that either all the parties learn the output of the function, or nobody does-- even when a majority of the parties are corrupted. We first propose a framework for fairmulti-party computation, within which we formulate a definition of secure and fair protocols. The definition follows the standard simulation paradigm, but is modified to allow the protocol to dependon the runing time of the adversary. In this way, we avoid a well-known impossibility result for fair MPC with corrupted majority; in particular, our definition admits constructions that tolerate upto ( n- 1) corruptions, where n is the total number of parties. Next, we define a "commit-prove-fair-open " functionality and construct an efficient protocol that realizes it, using a new variant of a cryptographic primitive known as "time-lines. " With this functionality, we show that some ofthe existing secure MPC protocols can be easily transformed into fair protocols while preserving their security. Putting these results together, we construct efficient, secure MPC protocols that arecompletely fair even in the presence of corrupted majorities. Furthermore, these protocols remain secure when arbitrarily composed with any protocols, which means, in particular, that they areconcurrently-composable and non-malleable. Finally, as an example of our results, we show a very efficient protocol that fairly and securely solves the socialist millionaires ' problem.
Abstract. We introduce the notion of resource-fair protocols. Informally, this property states that if one party learns the output of the protocol, then so can all other parties, as long as they expend roughly the same amount of resources. As opposed to similar previously proposed definitions, our definition follows the standard simulation paradigm and enjoys strong composability properties. In particular, our definition is similar to the security definition in the universal composability (UC) framework, but works in a model that allows any party to request additional resources from the environment to deal with dishonest parties that may prematurely abort. In this model we specify the ideally fair functionality as allowing parties to “invest resources ” in return for outputs, but in such an event offering all other parties a fair deal. (The formulation of fair dealings is kept independent of any particular functionality, by defining it using a “wrapper.”) Thus, by relaxing the notion of fairness, we avoid a well-known impossibility result for fair multi-party computation with corrupted majority; in particular, our definition admits constructions that tolerate arbitrary number of corruptions. We also show that, as in the UC framework, protocols in our framework may be arbitrarily and concurrently composed. Turning to constructions, we define a “commit-prove-fair-open ” functionality and design an efficient resource-fair protocol that securely realizes it, using a new variant of a cryptographic primitive known as “timelines.” With (the fairly wrapped version of) this functionality we show that some of the existing secure multi-party computation protocols can be easily transformed into resource-fair protocols while preserving their security. 1
A protocol for computing a functionality is secure if an adversary in this protocol cannot cause more harm than in an ideal computation where parties give their inputs to a trusted party which returns the output of the functionality to all parties. In particular, in the ideal model such computation is fair -- all parties get the output. Cleve (STOC 1986) proved that, in general, fairness is not possible without an honest majority. To overcome this impossibility, Gordon and Katz (Eurocrypt 2010) suggested a relaxed definition -- 1/p-secure computation -- which guarantees partial fairness. For two parties, they construct 1/p-secure protocols for functionalities for which the size of either their domain or their range is polynomial (in the security parameter). Gordon and Katz ask whether their results can be extended to multiparty protocols. We study 1/p-secure protocols in the multiparty setting for general functionalities. Our main result is constructions of 1/p-secure protocols when the number of parties is constant provided that less than 2/3 of the parties are corrupt. Our protocols require that either (1) the functionality is deterministic and the size of the domain is polynomial (in the security parameter), or (2) the functionality can be randomized and the size of the range is polynomial. If the size of the domain is constant and the functionality is deterministic, then our protocol is efficient even when the number of parties is O(log log n) (where n is the security parameter). On the negative side, we show that when the number of parties is super-constant, 1/p-secure protocols are not possible when the size of the domain is polynomial.
Abstract. This paper analyzes group communication within the universally composable framework. We first propose the group communication model, identity-based signcrytion mod-el and group key distribution model in the UC framework by designing the ideal functionality FSAGCOM, FIDSC and FGKD, respectively. Then, we construct a UC secure identity-based signcryption protocol πIDSC. Moreover, we shows that the identity-based signcryption πIDSC securely realizes the ideal functionality FIDSC if and only if the corresponding protocol ID-SC is secure. Finally, based on the identity-based protocol, we propose a group communica-tion scheme πSAGCOM, which can securely realizes the ideal functionality FSAGCOM in the (FIDSC,FGKD)-hybrid model.