Two Outsourced Attribute-based Cryptographic Schemes And Application

Attribute-based cryptosystems provide flexible and fine-grained access control and are attractive cryptographic primitives that have received wide attention from academia and industry.Attribute-based cryptosystems are cryptographic schemes that achieve access control through attributes and access structures defined on sets of attributes and are divided into attribute passwords based on key policies and attribute passwords based on ciphertext policies.In a key policy-based attribute cipher,the user obtains the key to the access structure from the attribute authority and decrypts(or signs the message)the cipher text of the attribute that satisfies its access structure.In contrast,the ciphertext of attribute-based cryptography is encrypted with the access structure and can be decrypted by the user who has the desired attribute.However,attribute-based cryptosystems have significant encryption and decryption overhead,which inconveniences users with limited resources.Outsourced computing is an important technology in cloud computing that allows users to securely outsource computing tasks to cloud services,which can significantly reduce users’ local computing overhead and solve the dilemma of resource-constrained users.Proxy reencryption is a type of outsourced computing that allows a user to delegate to a cloud server the re-encryption of ciphertexts sent to him by the data producer to other users.Outsourcing computing techniques and proxy re-encryption provide viable solutions for reducing computational overhead and securely sharing cloud data.In this paper,we investigate outsourced hybrid proxy re-encryption and outsourced attribute-based signatures and combine them with blockchain technology for the secure sharing of medical data.The details are as follows:1.Research and give the definition and security model of outsourced hybrid proxy reencryption from public key encryption to attribute-based encryption.Propose an outsourced hybrid proxy re-encryption scheme from public key encryption to attribute-based encryption.The scheme provides a new public key encryption scheme that facilitates data producers to encrypt data efficiently;provides a proxy re-encryption mechanism from public key encryption to attribute-based encryption that allows data owners to perform fine-grained decryption authorization;and introduces an outsourced decryption mechanism that makes it easy for users with limited resources to decrypt data.The proposed scheme is secure under selective ciphertext attacks.The performance analysis shows that the scheme has advantages in terms of both computational and storage overheads and is highly available.2.To propose an improved signature scheme based on outsourced attributes.Analysis of the outsourced attribute-based signature scheme proposed by Mo et al.shows that the scheme is not resistant to collusive attacks by adversaries and cloud servers,and also not resistant to privacy attacks by cloud servers.A new security model for outsourcing attribute-based signature privacy is proposed.The scheme of Mo et al.is improved to achieve all the security requirements while maintaining high efficiency.The improved scheme is provably secure under the standard model.3.To propose a blockchain-based cloud sharing scheme for medical data.The security and integrity of medical data sharing are ensured using the two attribute-based encryption schemes proposed above.Simulation experiments show that the scheme is efficient and feasible and has practical value.