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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]

Cloud storage technology has attracted a considerable number of users owing to its exponential growth. Storing data in the cloud can save the resources of local storage configuration and reduce the cost of local hardware investment. However, the data stored in the cloud is out of the physical control (out of control) of the user. Based on the service characteristics of the cloud environment and the security requirements of user privacy data in the cloud environment, this paper proposes an improved identity proxy re-encryption algorithm based on the advanced encryption standard algorithm. The performance of the algorithm is optimized by reducing the number of bilinear mapping operations, whose calculation takes the longest time in the proxy re-encryption scheme. Only two bilinear mapping operations are required in this scheme. In addition, the encrypted data are tested to different degrees. The experimental results show that this scheme satisfies encryption and decryption performance requirements of the user. [ABSTRACT FROM AUTHOR]

Advanced cloud computing technology provides cost saving and flexibility of services for users. With the explosion of multimedia data, more and more data owners would outsource their personal multimedia data on the cloud. In the meantime, some computationally expensive tasks are also undertaken by cloud servers. However, the outsourced multimedia data and its applications may reveal the data owner's private information because the data owners lose the control of their data. Recently, this thought has aroused new research interest on privacy-preserving reversible data hiding over outsourced multimedia data. In this paper, two reversible data hiding schemes are proposed for encrypted image data in cloud computing: reversible data hiding by homomorphic encryption and reversible data hiding in encrypted domain. The former is that additional bits are extracted after decryption and the latter is that extracted before decryption. Meanwhile, a combined scheme is also designed. This paper proposes the privacy-preserving outsourcing scheme of reversible data hiding over encrypted image data in cloud computing, which not only ensures multimedia data security without relying on the trustworthiness of cloud servers, but also guarantees that reversible data hiding can be operated over encrypted images at the different stages. Theoretical analysis confirms the correctness of the proposed encryption model and justifies the security of the proposed scheme. The computation cost of the proposed scheme is acceptable and adjusts to different security levels. [ABSTRACT FROM AUTHOR]

Cryptographic proxy re-encryption is a very useful primitive which is capable of transforming a ciphertext under one public key PK1 into a new ciphertext under another public key PK2 without private information leakage, while the two ciphertexts are encryptions of the same message. Re-encryption schemes at first are constructed under the public-key encryption (PKE) scenario. While it is a powerful primitive naturally required in not only PKE but also other scenarios, various extensions from PKE to other advanced encryption schemes like identity-based encryption (IBE), attribute-based encryption (ABE) as well as functional encryption (FE) are needed as well. In this work we have concentrated on how to reduce the workloads in the user/client side at large. To this end, we have put forth a novel identity-based proxy re-encryption (IBPRE) scheme with the feature that the re-encryption key gen­eration for the users is highly lightweight - actually almost free. Although this will lead to possibly extra decryption workload due to the utilization of homomorphic encryption, it is the first scheme realizing such almost free RK generation. In addition, it can also avoid some other shortcomings like re-encryption key management. [ABSTRACT FROM AUTHOR]

Outsource computing might reveal some private information in open cloud systems and the concern of users' privacy will be a crucial issue. Program obfuscation is an important cryptographic primitive that perfectly hides the secrets inside a program while preserving its functionality. In this paper, we give a two-form re-encryption scheme that achieves the security against adaptively chosen-ciphertext attacks, which allows any third party (e.g., cloud server) to re-encrypt the ciphertext that delegates the decryption right from one to another. However, as the third party knows the sensitive secret (i.e., re-key), and thus we should guarantee the trustworthy of this cloud server. Based the re-encryption algorithm, we propose an efficient obfuscator that implements the re-encryption functionality in such a way that not only the private information is protected but also cloud users' privacy is preserved, and thus the re-encryption procedure can be run on untrusted outsourcing server. We prove the virtual black-box security of the obfuscation. The proposed obfuscator can be run on untrusted server to help the perform of the functionality of re-encryption without any sensitive secret revealing. [ABSTRACT FROM AUTHOR]

To protect the sensitive data outsourced to cloud server, outsourcing data in an encrypted way has become popular nowadays. However, it is not easy to find the corresponding ciphertext efficiently, especially the large ciphertext stored on cloud server. Besides, some data owners do not want those users who attempt to decrypt to know the sensitive access structure of the ciphertext because of some business or private reasons. In addition, the user attributes revocation and key updating are important issues, which affect application of ciphertext-policy attribute-based encryption (CP-ABE) in cloud storage systems. To overcome the previous problems in cloud storage, we present a searchable CP-ABE with attribute revocation, where access structures are partially hidden so that receivers cannot extract sensitive information from the ciphertext. The security of our scheme can be reduced to the decisional bilinear Diffie-Hellman (DBDH) assumption and decisional linear (DL) assumption. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Deduplication, which stores only one copy of duplicate data, is used extensively in cloud storage to reduce the overhead associated with storage. Unfortunately, client-side encryption prevents cloud storage from performing deduplication due to the randomness of traditional encryption. Some existing schemes can balance encryption and deduplication, but their interaction with third-party servers or online users adds additional overhead to the system. Also, the ownership of outsourced data will change frequently due to users' requests to upload/delete/modify the data. But many existing schemes that can achieve dynamic ownership management have security flaws or require users to manage multiple keys. By focusing on these troubles, we have developed a secure deduplication scheme that does not rely on any third-party entities and supports data ownership management. More specifically, we take advantage of elliptic curve cryptography to design a key-sharing method so that different owners of the same data can share a random key only by interacting with the cloud service provider. And the broadcast encryption is used to manage the ownership of data, and this allows the cloud service provider to control users' access to outsourced data by updating the broadcast key. In addition, the security analysis shows that the proposed scheme can meet the required security and that it outperforms other related schemes. The detailed simulation comparisons with other related schemes demonstrate that the proposed scheme has good performance. [ABSTRACT FROM AUTHOR]

The intersection operation on multisets has many applications in different scenarios, such as data mining and pattern matching. This motivates us to study the problem that when users outsource their private encrypted sets and delegate the set-intersection operation on the corresponding plaintexts to the cloud, the cloud can manage to conduct the operation and make the result verifiable without the decryption capability. We formally introduced a model of Verifiable Intersection Operations on Encrypted Data in Cloud and presented the definitions of the correctness and security properties. We also proposed a concrete scheme basing on the bilinear-map accumulator and re-encryption. The scheme was proved secure under some cryptographic assumptions. And the experimental results of the algorithm implementation show the scheme is partly practical for real scenarios. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY Cloud computing as a promising technology and paradigm can provide various data services, such as data sharing and distribution, which allows users to derive benefits without the need for deep knowledge about them. However, the popular cloud data services also bring forth many new data security and privacy challenges. Cloud service provider untrusted, outsourced data security, hence collusion attacks from cloud service providers and data users become extremely challenging issues. To resolve these issues, we design the basic parts of secure re-encryption scheme for data services in a cloud computing environment, and further propose an efficient and secure re-encryption algorithm based on the EIGamal algorithm, to satisfy basic security requirements. The proposed scheme not only makes full use of the powerful processing ability of cloud computing but also can effectively ensure cloud data security. Extensive analysis shows that our proposed scheme is highly efficient and provably secure under existing security model. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Program obfuscation is a compiler that transfers a program into an unintelligible form while preserving the original functionality. Secure obfuscation for several particular function families has been raised out despite the general impossibility result presented by Barak et al. Re-encryption function is a useful primitive, which transforms ciphertexts for one party into ciphertexts under another party's public key. Hohenberger et al. constructed a special re-encryption function and securely obfuscated it in TCC'07, and the security is based on classical hardness assumption. In this paper, we construct a new re-encryption function and securely obfuscate it based on the standard learning with error (LWE) assumption. LWE is proved to be reducible to standard lattice problems, which are conjectured immune to quantum cryptanalysis or 'post-quantum'. Besides, we discuss about the relations between these two cryptographic primitives in detail: proxy re-encryption and obfuscation for re-encryption functions. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The anonymous channels have been the essence of numerous protocols that include anonymous message passing between peers. The mixnet structure is one way to accomplish the anonymity. Since the publication of the Chaumian mixnet, there have been many practical implementations. There are two main approaches to implement mixnets: the decryption (Chaumian) and the re-encryption mixnets. In this paper we analyze four types of mixnets, of which one decryption and three re-encryption types. They were implemented in the Java programing language and evaluated on several criterias as: the number of messages, the total number of nodes, the number of threshold nodes, and the key length of underlying crypto system. In the results section we compare the results from the practical tests to answer the research question, which type of mixnets has better features. [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]