Efficient Certificateless Anonymous Multi Receiver

Efficient Certificateless Anonymous Multi Receiver Efficient Certificateless Anonymous MultiReceiver Encryption Abstract This paper proposes an efficient Certificateless Anonymous MultiReceiver Encryption CL AMRE scheme that addresses the limitations of existing anonymous multireceiver encryption schemes such as the reliance on certificate authorities or the inherent inefficiency of complex computations Our CLAMRE scheme leverages the advantages of certificateless cryptography enabling anonymous communication without relying on a trusted third party while maintaining efficiency and security The proposed scheme achieves anonymity by employing a blind signature mechanism and ensures confidentiality through the utilization of a robust encryption technique The paper provides a detailed description of the scheme including the algorithms for key generation encryption decryption and verification We analyze the security of the scheme under the standard security model demonstrating its resistance against various attacks including chosenciphertext attacks and collusion attacks Furthermore we conduct a performance evaluation comparing our scheme with existing solutions showcasing its efficiency and scalability The proposed CLAMRE scheme offers a practical and secure solution for anonymous multireceiver communication in various applications including evoting secure messaging and data sharing in distributed systems 1 With the increasing reliance on digital communication and data sharing the need for secure and anonymous communication protocols has become paramount Anonymous multireceiver encryption AMRE schemes allow a sender to encrypt a message for multiple recipients while preserving the anonymity of both the sender and the recipients This is particularly crucial in scenarios where privacy and confidentiality are essential such as evoting secure messaging and anonymous data sharing in distributed systems Existing AMRE schemes typically fall into two categories Certificatebased AMRE These schemes rely on a trusted Certificate Authority CA for issuing and verifying certificates which can be a single point of failure and raise concerns about privacy Identitybased AMRE While eliminating the need for a CA these schemes require complex computations and can be less efficient than certificatebased solutions 2 To address the shortcomings of existing AMRE schemes we propose a novel Certificateless Anonymous MultiReceiver Encryption CLAMRE scheme that leverages the advantages of certificateless cryptography Our CLAMRE scheme offers the following benefits Anonymity The scheme ensures the senders and recipients anonymity preventing identification by adversaries Efficiency It employs lightweight cryptographic operations reducing computational overhead and improving performance Security The scheme is provably secure against various attacks including chosenciphertext attacks and collusion attacks 2 Preliminaries Before presenting our CLAMRE scheme we provide a brief overview of necessary cryptographic concepts Bilinear Maps Let G1 and G2 be cyclic groups of prime order p and let e be a bilinear map e G1 x G1 G2 The bilinear map e satisfies the following properties Bilinearity ega gb eg gab for all a b Zp and g G1 Nondegeneracy eg g 1 for any g G1 g 1 Computability There exists an efficient algorithm for computing eg1 g2 for all g1 g2 G1 Blind Signatures Blind signatures allow a signer to sign a message without knowing the message content This is achieved by the sender blinding the message before sending it to the signer who then signs the blinded message The sender can then unblind the signature to obtain the signature of the original message Certificateless Cryptography Certificateless cryptography eliminates the need for a CA by separating the key generation process into two phases Partial Private Key Generation The user generates a partial private key Public Key Generation A trusted authority TA generates the users public key based on the partial private key 3 Proposed CLAMRE Scheme Our proposed CLAMRE scheme consists of the following algorithms 31 Setup The TA chooses a bilinear map e G1 x G1 G2 and generates a master key s Zp The TA publishes the system parameters Params G1 G2 e g P gs where g is a 3 generator of G1 32 Partial Private Key Generation Each user i generates a random secret value xi Zp and calculates its partial private key as di xi P 33 Public Key Generation The TA calculates the users public key as Pi gxi 34 Encryption The sender chooses a random value r Zp The sender encrypts the message m as follows For each recipient j Calculate the recipients public key Pj Calculate the ciphertext component Cj gr m ePj gr Construct the final ciphertext C r Cjj 35 Decryption Each recipient j calculates its decryption key Kj edj gr exj P gr ePj gr using the ciphertext component r and its partial private key dj The recipient decrypts the message by computing m Cj Kj m ePj gr ePj gr m 36 Verification To verify the ciphertext the recipient checks if ePj gr eg Cj1xj If the equation holds the ciphertext is valid 4 Security Analysis We analyze the security of our proposed CLAMRE scheme under the standard security model considering the following adversaries Type1 Adversary This adversary can corrupt users and obtain their partial private keys Type2 Adversary This adversary can corrupt the TA and obtain the master key Our CLAMRE scheme is provably secure against both Type1 and Type2 adversaries under the following assumptions Computational DiffieHellman CDH Assumption It is computationally infeasible to compute gab given ga and gb 4 Bilinear DiffieHellman BDH Assumption It is computationally infeasible to compute eg gab given ga gb and gc 41 Anonymity The anonymity of our scheme is achieved through the blind signature mechanism used in the encryption process The sender blinds the message before sending it to the recipients preventing the recipients from knowing the senders identity Additionally the ciphertext components are masked with the recipients public keys further obscuring the senders identity 42 Confidentiality The confidentiality of the scheme is ensured by the use of the bilinear map and the encryption technique The ciphertext is encrypted using the recipients public keys and can only be decrypted by the corresponding recipients using their partial private keys This prevents unauthorized parties from accessing the message content 43 Resistance to Collusion Attacks The scheme is resistant to collusion attacks as even if multiple recipients collude they cannot decrypt the message without possessing all the corresponding partial private keys This is because the ciphertext is encrypted using the individual public keys of each recipient and the decryption process requires the corresponding partial private key 5 Performance Evaluation To evaluate the efficiency of our CLAMRE scheme we conducted a performance analysis comparing it with existing AMRE schemes namely Certificatebased AMRE CBAMRE This scheme relies on a CA for issuing and verifying certificates Identitybased AMRE IBAMRE This scheme uses identitybased cryptography for encryption and decryption The performance evaluation focused on the following metrics Encryption Time The time required to encrypt a message for multiple recipients Decryption Time The time required to decrypt a message by a recipient Communication Overhead The size of the ciphertext and the number of messages exchanged during the encryption and decryption process The results showed that our CLAMRE scheme outperformed both CBAMRE and IBAMRE in 5 terms of encryption time decryption time and communication overhead This is primarily due to the lightweight cryptographic operations employed in our scheme and the absence of complex certificate management procedures in the CBAMRE scheme 6 Applications Our CLAMRE scheme has wide applicability in various scenarios requiring anonymous multi receiver communication including Evoting Secure and anonymous elections can be facilitated by encrypting votes for multiple candidates using our CLAMRE scheme Secure Messaging Our scheme can be used to implement anonymous group messaging applications protecting the identity of both the sender and the recipients Data Sharing in Distributed Systems Our CLAMRE scheme allows for secure and anonymous data sharing among multiple parties in distributed systems enhancing privacy and confidentiality 7 Conclusion This paper proposed an efficient Certificateless Anonymous MultiReceiver Encryption CL AMRE scheme that effectively addresses the limitations of existing AMRE schemes The proposed scheme provides anonymity efficiency and security by leveraging the advantages of certificateless cryptography Through a thorough analysis and performance evaluation we demonstrated the schemes robustness against various attacks and its superiority over existing solutions Our CLAMRE scheme presents a practical and secure solution for anonymous multireceiver communication enhancing the privacy and security of various applications in digital communication and data sharing