Certificateless strong designated verifier signature schemes have realized the merit of CL-PKC against the traditional strong designated verifier signatures. However, when the signer and the designated verifier disagree with the signature, existing schemes cannot distinguish the original signature from the signature transcript. In addition, errors or malicious actions introduced by the designated verifier may lead to the failure of signature verification. To solve these issues, we propose a certificateless verifiable strong designated verifier signature scheme. When disputes arise between the signer and the verifier, the scheme can effectively prevent the signer from denying the signature generated by the signer, as well as the designated verifier from denying valid signatures or invalid ones. Our scheme does not rely on bilinear pairings. The proposed scheme satisfies the requirements of verifiability, unforgeability, non-delegability, non-transferability and signer ambiguity. We also provide formal security proof in the random oracle model for the proposed scheme. INDEX TERMS Certificateless signature, strong designated verifier signature, ECDLP, verifiable.

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As special types of factorization of finite groups, logarithmic signatures and covers have been used as the main components of cryptographic keys for secret key cryptosystems such as PGM and public key cryptosystems like MST 1 , MST 2 , MST 3 and eMST 3. In particular, as a natural analogue of integer factorization problem (IFP), group factorization problem (GFP) and its hardness assumption over certain factorization basis, referred as logarithmic signature, play a core role in the security arguments for the family of MST cryptosystems. Security is not the unique goal of designing a cryptosystem. Instead, efficiency is also a major issue. In this paper, we design a new secure encryption scheme based on group factorization problem (GFP). Furthermore, we present the security analysis and demonstrate the performance of our scheme. Comparing with eMST 3 , our scheme is simplified with more efficiency.

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As cloud storage technology develops, data sharing of cloud-based electronic medical records (EMRs) has become a hot topic in the academia and healthcare sectors. To solve the problem of secure search and sharing of EMR in cloud platforms, an EMR data-sharing scheme supporting multi-keyword search is proposed. The proposed scheme combines searchable encryption and proxy re-encryption technologies to perform keyword search and achieve secure sharing of encrypted EMR. At the same time, the scheme uses a traceable pseudo identity to protect the patient’s private information. Our scheme is proven secure based on the modified Bilinear Diffie-Hellman assumption and Quotient Decisional Bilinear Diffie-Hellman assumption under the random oracle model. The performance of our scheme is evaluated through theoretical analysis and numerical simulation.