Researches On Secure Multi-party Computing Protocol And Applications

Technological progress has greatly improved the production and lifestyle of mankind.More information is digitized and stored in the cloud,making it very convenient to share and use data.While enjoying the fruits of the tech-nological revolution,mankind also faces a huge risk of privacy leakage.The continuous optimization of data mining algorithms has exposed more private information to the public's field of vision.Secure multi-party computing is an advanced technical means to solve the problem of privacy leakage,which can effectively protect the privacy input of the parties to the agreement.The schol-ars have adopted a secure multi-party computing design to achieve a variety of functions,while also protecting the privacy and sensitive information of users.On the other hand,secure multi-party computing consumes huge computing and communication resources,which also limits the application and popular-ization of secure multi-party computing.In the past two decades,research on secure multi-party computing has advanced by leaps and bounds,and scholars have made great strides in security theory,computing efficiency,and practical functions.This thesis takes the secure multi-party computing protocol and its appli-cation as the research point to design a cryptographic protocol that meets the needs of privacy protection and has practical significance.The research results obtained are as follows:Firstly,this thesis uses the secure comparison protocol to construct a multi-user multi-keyword public key searchable encryption algorithm.The security comparison protocol can compare the size of the private input of the partici-pants without revealing the private input of the participants.This property sat-isfies the need to determine whether the keywords on the cloud server match the user keywords and not leak the keywords in searchable encryption.In this thesis,a secure comparison protocol is designed by using single homomorphic encryption.The homomorphic operation in the protocol satisfies the commu-tative law,and the superposition of multiple keywords can be realized with-out affecting the matching result.Based on this principle,this thesis designs four schemes that balance calculation efficiency and function:A multi-keyword public key searchable encryption scheme that can be calculated quickly;a multi-keyword public key searchable encryption scheme based on keyword sorting;a multi-user,multi-keyword public key searchable encryption scheme that can be quickly calculated;keyword-based sorting Multi-user multi-keyword public key searchable encryption scheme.The scheme proposed in this thesis adapts to different user scenarios,and the efficiency decreases with the increase of func-tions.Compared with other schemes,the scheme proposed in this thesis has the characteristics of fast computing speed and suitable for lightweight equipment.Secondly,this thesis designs a broadcast encryption algorithm based on secret sharing and deploys it in the blockchain network to avoid traitors.The secret sharing protocol is one of the primitive algorithms for secure multi-party computing,and it has the function of safely distributing private values.The broadcast encryption designed by the linear secret sharing scheme adopted in this thesis deploys the private value containing part of the master private key information to the blockchain network.The recovery of the private value re-quires the assistance of the blockchain network to complete the decryption pro-cess of the broadcast encryption.In this calculation process,the secret sharing share is encapsulated by a homomorphic calculation,and the new encapsulated secret value calculation result is exactly the part needed for decryption.The original share will not be exposed,and any information of the master private key will not be exposed.Compared with traditional broadcast encryption,the secret sharing-based broadcast encryption scheme deployed in the blockchain network proposed in this article no longer requires an issuer,effectively pre-venting the existence of a decryption black box,and the size of the ciphertext and key is not significantly expanded.Thirdly,this thesis uses blockchain computing power to calculate secure multi-party computing protocols,thereby avoiding the waste of blockchain re-sources and increasing the practicability of secure computing.Proof of work is a common consensus mechanism in blockchain.By finding the input of a hash algorithm with a special value range,it is currently widely used proof of work.The scheme proposed in this thesis uses miners to execute the secure computing protocol.In the process,evidence of the zero-knowledge proof pro-tocol will be generated,which guarantees the correctness and safety of secure multi-party computing and also proves the workload of the miners.This design can turn the originally meaningless hash function calculation into a feature-rich secure multi-party calculation.This thesis designs the secure computing process,blockchain structure,consensus mechanism,etc.under the new inter-active mode,which avoids the waste of blockchain resources while meeting the needs of secure multi-party computing.