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In today's globalized agricultural system, information leakage of agricultural biological risk factors can lead to business risks and public panic, jeopardizing corporate reputation. To solve the above problems, this study constructs a blockchain network for agricultural product biological risk traceability based on agricultural product biological risk factor data to achieve traceability of biological risk traceability data of agricultural product supply chain to meet the sustainability challenges. To guarantee the secure and flexible sharing of agricultural product biological risk privacy information and limit the scope of privacy information dissemination, the blockchain-based proxy re-encryption access control method (BBPR-AC) is designed. Aiming at the problems of proxy re-encryption technology, such as the third-party agent being prone to evil, the authorization judgment being cumbersome, and the authorization process not automated, we design the proxy re-encryption access control mechanism based on the traceability of agricultural products' biological risk factors. Designing an attribute-based access control (ABAC) mechanism based on the traceability blockchain for agricultural products involves defining the attributes of each link in the agricultural supply chain, formulating policies, and evaluating and executing these policies, deployed in the blockchain system in the form of smart contracts. This approach achieves decentralization of authorization and automation of authority judgment. By analyzing the data characteristics within the agricultural product supply chain to avoid the malicious behavior of third-party agents, the decentralized blockchain system acts as a trusted third-party agent, and the proxy re-encryption is combined with symmetric encryption to improve the encryption efficiency. This ensures a efficient encryption process, making the system safe, transparent, and efficient. Finally, a prototype blockchain system for traceability of agricultural biological risk factors is built based on Hyperledger Fabric to verify this research method's reliability, security, and efficiency. The experimental results show that this research scheme's initial encryption, re-encryption, and decryption sessions exhibit lower computational overheads than traditional encryption methods. When the number of policies and the number of requests in the access control session is 100, the policy query latency is less than 400 ms, the request-response latency is slightly more than 360ms, and the data uploading throughput is 48.7 tx/s. The data query throughput is 81.8 tx/s, the system performance consumption is low and can meet the biological risk privacy protection needs of the agricultural supply chain. The BBPR-AC method proposed in this study provides ideas for achieving refined traceability management in the agricultural supply chain and promoting digital transformation in the agricultural industry. [ABSTRACT FROM AUTHOR]

As a result of the declaration of the COVID-19 pandemic, several proposals of blockchain-based solutions for digital COVID-19 certificates have been presented. Considering that health data have high privacy requirements, a health data management system must fulfil several strict privacy and security requirements. On the one hand, confidentiality of the medical data must be assured, being the data owner (the patient) the actor that maintain control over the privacy of their certificates. On the other hand, the entities involved in the generation and validation of certificates must be supervised by a regulatory authority. This set of requirements are generally not achieved together in previous proposals. Moreover, it is required that a digital COVID-19 certificate management protocol provides an easy verification process and also strongly avoid the risk of forgery. In this paper we present the design and implementation of a protocol to manage digital COVID-19 certificates where individual users decide how to share their private data in a hierarchical system. In order to achieve this, we put together two different technologies: the use of a proxy re-encryption (PRE) service in conjunction with a blockchain-based protocol. Additionally, our protocol introduces an authority to control and regulate the centers that can generate digital COVID-19 certificates and offers two kinds of validation of certificates for registered and non-registered verification entities. Therefore, the paper achieves all the requirements, that is, data sovereignty, high privacy, forgery avoidance, regulation of entities, security and easy verification. [ABSTRACT FROM AUTHOR]

Storing only one unique copy of the same cloud data and guaranteeing its integrity are two main goals for cloud storage auditing and deduplication schemes. In such schemes, data owners can firmly believe the data integrity by periodically auditing and the cloud server can save lots of storage space by exploiting the duplication techniques. However, when a data owner deletes or modifies his outsourced data, he should lose the ownership for the original data and should not be able to successfully retrieve this data any more. For all we know, existing cloud storage auditing and deduplication literatures fail to support the modifications of ownership, which actually occur quite often in actual cloud storage scenarios. In this paper, we propose the first deduplicated data integrity auditing scheme supporting the ownership modification. It guarantees the integrity of the outsourced data and supports the dynamic access control over the outsourced data. We employ a re-encryption algorithm and the secure identity-based broadcast encryption technology, which prevent data from being disclosed to the revoked owners, even if they previously had prior ownership of these data. The security and efficiency of our proposed scheme have been validated by detailed analysis and experiments. [ABSTRACT FROM AUTHOR]

Cloud data sharing allows users to access data stored on the web object. Security and protecting cloud data sharing form different attacks is recently considered one of the most challenges. In this paper, we are proposing a framework for cloud data sharing protection against unauthorized access. The proposed framework is based on DNA-proxy re-encryption. Firstly, three keys are generated for the owner, proxy and the user who need to access the data. Then, the owner stores his data encrypted on the cloud using his key. If the user wants to access this data then he can access it via the proxy after re-encrypting using the second generated key for the proxy. Finally, the user can decrypt the re-encrypted data with the third generated key. The framework was implemented using various plaintext files and real DNA sequences. The experimental results show that the framework has an outstanding performance in terms of execution time. [ABSTRACT FROM AUTHOR]

Recently, cloud computing becomes a main platform for the distribution of multimedia content. The paradigm of multimedia distribution has been shifted from the models in traditional ways to the one in cloud computing. Security and privacy are two most important issues in multimedia distribution. The new model in cloud computing concerns the following issues. Firstly, outsourced content should be confidential except a data owner (DO). Secondly, the CSP is semi-trusted in the public cloud computing environment. A malicious data user (DU) may collude with the CSP to harm the DO's rights and interests. Thirdly, the rights and interests of DU, including anonymity and unlinkability, should be protected. Based on the above problems, we propose and analyze a Multimedia Distribution based Re-encryption and Fingerprinting (MDRF) scheme in cloud computing. The proposed scheme 1) allows efficient distribution of the content while preserving security and privacy of copyright holders and end users, 2) resolve the problems of piracy tracing, collusion resistance, and dispute resolution, and 3) protect the rights and interests of DU, including anonymity and unlinkability. The analysis part demonstrates that the security of DO and DU are well provided in the proposed scheme. The experimental results evaluate the performance of our framework in terms of collusion resistance of the fingerprint and imperceptibility of fingerprint embedding. [ABSTRACT FROM AUTHOR]

With the increasing number of mobile applications and the popularity of cloud computing, the combination of these two techniques that named mobile cloud computing (MCC) attracts great attention in recent years. However, due to the risks associated with security and privacy, mobility security protection in MCC has become an important issue. In this paper, we propose an efficient traceable access control scheme with reliable key delegation named KD-TABE in MCC. Firstly, we present a traceable CP-ABE system and realize key delegation without loss of traceability. Secondly, a new type of re-encryption method is proposed, which is based on an intuitive method that supports any monotonic access tree instead of the re-encryption key. Lastly, to reduce trust on authority, we separate the authority into three parts, and each authority is responsible for generating different components of the key. The analysis shows that the proposed scheme can meet the security requirement of MCC. In addition, it cost less compared with the other popular models. [ABSTRACT FROM AUTHOR]

A proxy re-encryption (PRE) scheme allows a semi-trusted proxy to convert a ciphertext intended for some recipient, say Alice, into another ciphertext which can only be decrypted by the other designated one, say Bob. It is required that the semi-trusted proxy cannot learn any information about the encrypted message. When a PRE scheme enables the semi-trusted proxy to convert a ciphertext intended for Alice into the one intended for Bob and then again convert this ciphertext into another one intended for Candy and so on, it is called multi-hop PRE scheme. In this paper, the author will propose a new multi-hop PRE scheme for secure content distribution. The security assumption is based on the bilinear inverse Diffie-Hellman problem. Compared with related PRE schemes, ours can earn more computational efficiency. [ABSTRACT FROM AUTHOR]

We present a positive obfuscation result for a traditional cryptographic functionality. This positive result stands in contrast to well-known impossibility results (Barak et al. in Advances in Cryptology-CRYPTO'01, ), for general obfuscation and recent impossibility and implausibility (Goldwasser and Kalai in 46th IEEE Symposium on Foundations of Computer Science (FOCS), pp. 553-562, ) results for obfuscation of many cryptographic functionalities. Whereas other positive obfuscation results in the standard model apply to very simple point functions (Canetti in Advances in Cryptology-CRYPTO'97, ; Wee in 37th ACM Symposium on Theory of Computing (STOC), pp. 523-532, ), our obfuscation result applies to the significantly more complex and widely-used re-encryption functionality. This functionality takes a ciphertext for message m encrypted under Alice's public key and transforms it into a ciphertext for the same message m under Bob's public key. To overcome impossibility results and to make our results meaningful for cryptographic functionalities, our scheme satisfies a definition of obfuscation which incorporates more security-aware provisions. [ABSTRACT FROM AUTHOR]