Secret Sharing And It's Applications In Proxy Signature

Secret sharing is an important method to realize the information security and data encryption.The concept of secret sharing was invented independently by Shamir and Blakley in 1979,which basic idea is to divide the secret into pieces and distribute the pieces to different persons so that certain subsets of them can get together to recover the secret when it is needed.With the rapid development of the computer network environment,traditional handwritten signature was replaced by digital signature;the latter was widely used in military,communication and e-commerce etc.In 1996,Mambo,Usuda and Okamoto firstly advanced the concept of proxy signature.A certain proxy signature signer can sign on behalf of an original signer in a proxy signature scheme.Proxy signature is a useful method in delegating signer's signing authority.The research of this dissertation focuses on secret sharing(especially publicly verifiable secret sharing) and it's applications in proxy signatures.Main contributions of this paper are summarized as follows:1.A new dynamic threshold multi-secret sharing scheme was proposed.In the scheme,the shares were choused and kept secretly by the participants themselves and the shares can be used repeatedly and needn't be redistributed when the participants join or leave dynamically.At the same time,all the secrets can be recovered in one time.2.A new proxy multi-signature scheme was proposed.The advantage of this scheme is protecting the identities of proxy signers,at the same time,when someone abuses his proxy sign right,his identity can be known.The scheme satisfies following security properties:strong unforgeability;fair identifiability;verifiability;strong undeniability et al.3.The concepts of shared verification and signcryption were introduced into proxy multi-signature,and a secure and efficient proxy multi-signcryption scheme with shared verification was presented,which was based on elliptic curves cryptosystem.In the scheme,a proxy signer can signcrypt a message on behalf of some original signers,and only t or more verifiers of the specified group together can recover the message,verify the validity of proxy signcryption.The scheme also had the merits of secrecy,public verifiability and strong undeniability,strong unforgeability et al.4.A new efficient ID-based threshold proxy signature scheme from bilinear pairings was proposed.The scheme can withstand the conspiracy attack.Furthermore, the proxy signer's proxy signing capability can be revoked by the original signers and the proxy signer's proxy signing secret key can be changed conveniently.