Research On Multi-signature And Proxy Re-Cryptography Algorithms

As an important carrier in the current network environment,information has been integrated into every aspect of people's lives.At the same time of information exchange and input output,the security of information has become the focus and goal of people's increasing attention.Signature and encryption are cryptography technologies that ensure the non-forgery,non-repudiation,security,and integrity of data.And the application environment and situation of signature and encryption technology can make the technology should also meet its particularity.General digital signature technology provides an application scenario for a single signatory to sign a document.In many practical cases,however,this would require multiple parties to sign a document together for it to take effect.Such as in e-commerce,internet of vehicles,expert consultation,electronic contract signing.The signature mode of multi-signature adds some flexibility to the signature technology application.The introduction of proxy re-cryptography technology realizes the conversion of existing signatures or ciphertexts without disclosing private information.Because of the special nature of proxy re-cryptography technology,it can be applied to many practical scenarios such as cloud computing,blockchain,distributed file system,digital copyright protection,etc.Based on the study of multi-signature and proxy re-cryptography,the following three algorithms are proposed:Firstly,based on Bilinear Pairing,a new certificateless broadcast multi-signature algorithm is constructed in this thesis.After combining the existing schemes,this thesis puts forward a formal definition and security model and proves that the algorithm meets the non-forgery in the random oracle model.Finally,based on the efficiency analysis and the analysis of numerical simulation experiments,this thesis shows that the algorithm reduces the operation time to a certain extent.In addition,this thesis also expands the multi-message certificateless broadcast multi-signature algorithm,which can meet the correctness and non-forgery.Secondly,by using Integer Factorization,this thesis proposes an id-based partially blind proxy re-signature algorithm without pairing,and gives formal definition and security model under the framework of identity cryptosystem and partial blindness.The algorithm can not only realize the transparent transformation between the original signature and the proxy re-signature,protect the privacy of the trustee and the delegate,and effectively reduce the operation of the partially blind proxy re-signature algorithm.Under the random oracle model,this thesis proves that the algorithm can satisfy the non-forgery and partial blindness of the message.Finally,through efficiency analysis and comparison,this thesis concludes that the algorithm still has a comparative advantage in its computational efficiency under the premise of combining partial blindness.Thirdly,this thesis presents a blockchain-based electronic medical record data sharing algorithm based on proxy re-encryption,which can enable third-party data users to share patient data without infringing on patient privacy.Constructed on the structure of private blockchain and consortium blockchain,the algorithm uses keyword search encryption technology to realize the secure search of keywords on the consortium blockchain,and uses proxy re-encryption technology to enable third-party data users to safely access patient data.The algorithm contains system model,private blockchain and consortium blockchain design and security targets.Through the security analysis and performance,this thesis analyzes that the algorithm has high computational efficiency and applicability.