Analysis And Improvement Of Certificateless Cryptographic Schemes

With the advent of the Internet of Everything and the transmission of massive amounts of data in public networks,it has become particularly important to ensure the secure transmission of data in public networks.Cryptographic techniques can protect data information by using conversion methods agreed between the two communicating parties,effectively guaranteeing the secure transmission of data.As a new cryptographic technique without the complex certificate management problem and the key escrow problem,the certificateless cryptosystem has been widely used in the design of signature,aggregate signature and signcryption schemes.However,some existing certificateless cryptographic schemes are still unable to resist collusion attacks and forgery attacks by Type I attackers and Type II attackers,making it difficult to ensure the secure transmission of data and information.Therefore,analyzing the security of existing certificateless cryptographic schemes and constructing more efficient and secure cryptographic schemes are of great theoretical significance and practical value for ensuring the secure transmission of data.We analyze and study certificateless signature,certificateless aggregate signature,and certificateless signcryption techniques,and complete the following work.(1)By analyzing an existing certificateless signature scheme,it is pointed out that this scheme is difficult to resist forgery attacks by Type II attackers and does not satisfy the claimed unforgeability.To solve this problem,a new certificateless signature scheme is constructed.The new scheme utilizes hash function to realize the close relationship between the system’s main public key and the user’s public key,which breaks the original linear relationship and prevents the attacker from forging legal signatures by bypassing the secret value.The analysis results show that the new scheme is more secure and has higher computational efficiency and communication efficiency.(2)By analyzing a certificateless aggregate signature scheme applied in a multi-party contract signing protocol,it is pointed out that this scheme is difficult to resist public key substitution attacks and collusion attacks,and specific attack methods are provided.To solve this problem,a new scheme which can resist public key substitution attacks and collusion attacks is constructed using anti-collision hash functions.The analysis results show that the new scheme has higher security,can ensure the secure transmission of information,and is suitable for multiparty contract signing environments.(3)By analyzing an existing certificateless signcryption scheme,it is pointed out that this scheme is difficult to resist two types of forgery attacks by Type II attackers,and does not have the unforgeability under the selective message attack.To solve this problem,a new certificateless signcryption scheme is constructed,and it is proved that the new scheme satisfies confidentiality and unforgeability under the random oracle model.Compared with similar schemes,the new scheme has lower communication and computational costs.