Research On Certificateless Proxy Signature Schemes

Digital signature is one of the cores of cryptography technology. The proxy signature,which is one of special digital signatures, was proposed by Mambo in1996. In a proxysignature scheme, the original signer authorizes a proxy signer as his proxy agent, who couldsign messages on behalf of the original signer. Proxy signature is widely applied ine-commerce, electronic auction, etc. In2003, Shamir presented the concept of CertificatelessPublic Key Cryptosystems (CL-PKC), and solved the certificate management problems intraditional Public Key Cryptography and key escrow problem in Identity-based Public KeyCryptography. In CL-PKC, the Key Generator Center (KGC) does not know user’s fullprivate key, thus the signature can achieve real unforgeablity.Combining CL-PKC with proxy signature, Li firstly presented a certificateless proxysignature scheme in2005, and since then, some certificateless proxy signature schemes havebeen proposed. All of them are based on the bilinear pairings, which lead to low efficiency andcomplex operation. In2013, He presented a certificateless proxy signature scheme withoutbilinear pairings, and proved its security under the random oracle model (ROM) based on DLP.Although certificateless proxy signature schemes without pairings have high efficiency, thelengths of them are relatively long.The certificateless proxy signature is investigated concretely, that is,(1) certificatelesssignature scheme without pairings,(2) certificateless proxy signature without pairings, and (3)certificateless proxy blind signature. The major contributions of the dissertation are as follows:1) We propose a concrete certificateless signature scheme without pairings (ZLX scheme),prove its security in the Random Oracle Model based on discrete logarithm problem, and analysesits efficiency. The result shows that signature length in our scheme is shorter than that of othercertificateless signature schemes without pairings;2) A certificateless proxy signature scheme without pairings (ZLT scheme) is proposedbased on ZLX scheme. Through the security analysis, the scheme satisfies the property ofexistential unforgeability under adaptively-chosen-massage-and-identity attacks. Thesignature length in ZLX scheme is shorter than He scheme.3) The certificateless proxy blind signature scheme proposed by Yu Dan is analysised.When the original signer A generates the proxy key for the proxy signer B, he may leak hisprivate keyS Ato B. We improve the scheme, and put forward a secure certificateless proxyblind signature scheme. Through the security analysis, the result shows that the scheme satisfies the security properties of the certificateless proxy blind signature.