To verify that an organization-friendly blockchain system may suffer from forgery and collusion attacks,forgery and collusion attacks were theoretically carried out according to the phase sequence of an organization-friendly blockchain system.Then,the organization-friendly blockchain system was improved and based on the phase sequence forgery and collusion attacks were conducted.The results show that the attacker can obtain illegal transaction data from forgery and collusion attacks on the organization-friendly blockchain system.However,for the improved organization-friendly blockchain,the attacker s forgery and collusion attacks cannot be completed.Therefore,the organization-friendly blockchain system may be subject to forgery and collusion attacks,but the improved organization-friendly blockchain system can prevent such attacks.
To share data securely with secure attribute revocation,anti-collusion,and dynamic user management in the 5G device-to-device(D2D)environment,a novel dynamic anti-collusion ciphertext policy attribute-based encryption(NDA-CP-ABE)scheme in the 5G D2D environment is proposed.On the basis of the ciphertext policy attribute-based encryption algorithm,fine-grained access control and secure attribute revocation are realized,and the confidentiality of data is guaranteed.A polynomial function is adopted in the ciphertext generation phase to realize dynamic user management.A random number is used to prevent a collusion attack among the legitimate user equipment(UE),revoked UE,and external network attackers.Finally,on the basis of the Diffie-Hellman problem,the NDA-CP-ABE scheme is formally proved,and the simulation performances are compared with those of similar schemes.The results show that data can be securely shared through a D2D channel with secure attribute revocation,anti-collusion,and dynamic user management.Moreover,compared with similar schemes,the NDA-CP-ABE scheme has higher efficiency in encryption,decryption,and storage.
