Recently,preserving theprivacy has attracted significant attention among weather societies, goverments and lawmakers. Anythingthata personfreely decides not to reveal, is commonly considered as a part of his privacy.Privacy preserving is necessary for using many network-based and other applications.Addressingthischallengeandaddingprivacyentailsmany benefits.Secure multiparty computation, a branch in cryptography, is a solution for this problem.The ideawas bornin the 1980s andmost of related studieshas beendirectedtomeet the theoretical challenges.One of these studies is to provide software frameworks,allowingresearchers to implementthe idea of secure multipartycomputation.In this thesis four frameworks of this category have been studied and two of them have been improved.Specifically,by changing the procedure ofsecret sharing,security and flexiblityofone frameworkisimproved.How to sharethe secrets have a direct impactonother components oftheframework. Accordingly,the necessary changes inthe addition and multiplication protocols, the basic protocols of such frameworks, has been applied. For this purpose,a modified versionofapreviouslyproposedmultiplication protocolissuggested. In allframeworksintroducedinthisthesis, multiplicationprotocolisone of the mainbottlenecksboth in terms of the computaions and communication. In this regard, for one of the frameworks, a new protocol is suggested to replace the original multiplication protocol in order to reduce the amount of required computation for each party.Moreover, usinganoptimized verifiable secretsharing scheme, security against a static active enemy is added to multiplication and additon protocols. Since the multiplication protocol is a basis for other protocols, the security of the whole framework can beimproved against the static active enemy. Keywords: Secure Multiparty Computation, Secure Protocols, Cryptography.
