Broadcast Re-encryption Research Articles

Conditional Proxy Re-Encryption-Based Key Sharing Mechanism for Clustered Federated Learning

The need of data owners for privacy protection has given rise to collaborative learning, and data-related issues heterogeneity faced by federated learning has further given rise to clustered federated learning; whereas the traditional privacy-preserving scheme of federated learning using homomorphic encryption alone fails to fulfill the privacy protection demands of clustered federated learning. To address these issues, this research provides an effective and safeguarded answer for sharing homomorphic encryption keys among clusters in clustered federated learning grounded in conditional representative broadcast re-encryption. This method constructs a key sharing mechanism. By combining the functions of the bilinear pairwise accumulator and specific conditional proxy broadcast re-ciphering, the mechanism can verify the integrity of homomorphic encryption keys stored on cloud servers. In addition, the solution enables key management centers to grant secure and controlled access to re-encrypted homomorphic encryption keys to third parties without disclosing the sensitive information contained therein. The scheme achieves this by implementing a sophisticated access tree-based mechanism that enables the cloud server to convert forwarded ciphertexts into completely new ciphertexts customized specifically for a given group of users. By effectively utilizing conditional restrictions, the scheme achieves fine-grained access control to protect the privacy of shared content. Finally, this paper showcases the scheme’s security against selective ciphertext attacks without relying on random prediction.

Toward Data Transmission Security Based on Proxy Broadcast Re-encryption in Edge Collaboration

With the development of IoT, more and more data is offloaded from the cloud to the edge for computing, eventually forming a collaborative computing model at the edge. However, in this model, the problem of secure data transmission has not been solved. In this model, data is transmitted and forwarded in multiple messaging systems, and existing security schemes cannot achieve end-to-end security in a multi-hop, broadcast transmission model. Therefore, in this paper, we propose a new security scheme based on proxy re-encryption and broadcast encryption techniques. Moreover, the performance and security of the scheme are further enhanced by using online-offline techniques and a trusted execution environment when integrating the scheme with edge collaboration. Finally, this paper proves the security of the scheme in theory, compares the functionality of the scheme, analyzes the theoretical performance of the scheme, and finally measures the actual performance of the scheme in the edge collaboration system.

A CCA-secure multi-conditional proxy broadcast re-encryption scheme for cloud storage system

Conditional proxy re-encryption allows a semi-trusted third-party proxy to convert Alice's ciphertext that meets a certain condition into another set of ciphertext. Meanwhile, the proxy cannot obtain any valuable information in the process. Nevertheless, a single re-encryption condition is difficult to meet the needs of practical applications, and the existing conditional proxy re-encryption scheme cannot flexibly control the conversion conditions. To solve this problem, this paper proposes a multi-conditional proxy broadcast re-encryption (MC-PBRE) scheme for file sharing systems. In our scheme, a single user can delegate the decryption rights of the encrypted file to a group of users. At the same time, users can set any number of conditions to control the user group decryption permissions. This paper demonstrates the security of the scheme for chosen-ciphertext attacks in the standard model. Furthermore, the program can resist collusion attacks, which means that the agent cannot collude with the user group to get the private key of the principal.

Conditional proxy broadcast re-encryption with fine grain policy for cloud data sharing

Conditional proxy broadcast re-encryption (CPBRE) enables a semi-trusted proxy to convert Alice's ciphertext satisfying a certain condition into a set of users' ciphertext. The proxy, however, cannot learn anything about the underlying plaintext. The traditional CPBRE schemes cannot support flexible control on conditions. In this paper, we present a new primitive named conditional proxy broadcast re-encryption with fine grain policy (CPBRE-FG). In a CPBRE-FG scheme, the re-encryption key is generated with an access tree, and the ciphertext is constructed under a set of descriptive conditions. The proxy can convert a ciphertext if and only if the set of conditions satisfies the access tree. We formalise the notion of CPBRE-FG and present an efficient CPBRE-FG scheme. Finally, we prove it against chosen-ciphertext attack (CCA) security in the random oracle model.

Conditional proxy broadcast re-encryption with fine grain policy for cloud data sharing

Conditional proxy broadcast re-encryption (CPBRE) enables a semi-trusted proxy to convert Alice's ciphertext satisfying a certain condition into a set of users' ciphertext. The proxy, however, cannot learn anything about the underlying plaintext. The traditional CPBRE schemes cannot support flexible control on conditions. In this paper, we present a new primitive named conditional proxy broadcast re-encryption with fine grain policy (CPBRE-FG). In a CPBRE-FG scheme, the re-encryption key is generated with an access tree, and the ciphertext is constructed under a set of descriptive conditions. The proxy can convert a ciphertext if and only if the set of conditions satisfies the access tree. We formalise the notion of CPBRE-FG and present an efficient CPBRE-FG scheme. Finally, we prove it against chosen-ciphertext attack (CCA) security in the random oracle model.

A Secure Multimedia Data Sharing Scheme for Wireless Network

A large number of wireless devices like WiFi cameras and 4G robots have been deployed in the rapidly growing wireless network such as Internet of Things. All of the devices (sensors) are collecting and analyzing multimedia data all the time while they are actively working, and it is also required to share data among these the sensors. Typically, the wireless data is transmitted through the network gateway or the cloud platforms. In such a wireless environment, if there is no appropriate protection to the data, it is easy to cause potential data leakage. In reality, the owner of the sensor might only want to share the multimedia data stored in the sensor with a trusted third party (e.g., a family member or a coworker) through an internet gateway or the cloud platform. Ideally, the gateway or the cloud platform in the wireless network should transform one user’s encrypted data (wireless multimedia data) directly into another ciphertext under a set of new users (e.g., a trusted third party) without accessing the user’s plaintext data. In this work, a new secure notion called fuzzy-conditional proxy broadcast re-encryption (FC-PBRE) is presented to address the concern. In a FC-PBRE scheme, the proxy (the gateway or cloud server) uses a broadcast re-encryption key to re-encrypt the encrypted wireless multimedia data which can be decrypted by a set of delegatees if and only if the broadcast key’s conditional set W is close to the conditional set W′ of the ciphertext. With the FC-PBRE scheme, the wireless multimedia data is not disclosed and cannot be learnt by the proxy (the gateway or cloud server). In this paper, we first present the definition of security against chosen-ciphertext attacks for FC-PBRE. Second, we propose an efficient fuzzy-conditional proxy broadcast re-encryption scheme. Third, we prove that our FC-PBRE scheme is CCA-secure in the random oracle model based on the Decisional nBDHE assumption.

Privacy preserving cloud data sharing system with flexible control

With the development of cloud technology, sharing date between users securely becomes more and more important. Moreover, the cloud server should provide a flexible control on sharing date. This work presents a notion named fuzzy conditional broadcast proxy re-encryption (FC-BPRE), in which a semi-honest proxy can transform a delegator’s ciphertext to a new ciphertext for a set of delegatees when the ciphertext satisfies a certain condition set by the delegator. However, the proxy cannot learn any useful information about the underlying plaintext. The proxy can convert a ciphertext, encrypted under a condition set W, to a ciphertext encrypted under a condition set W′ using a broadcast re-encryption key, if and only if S and S′ are close to each other. We first formalize the notion of FC-PBRE scheme and then proposed a construction.

A proxy broadcast re-encryption for cloud data sharing

Proxy re-encryption (PRE) enables a semi-trusted proxy to automatically convert a delegator’s ciphertext to a delegate’s ciphertext without learning anything about the underlying plaintext. PRE schemes have broad applications, such as cloud data sharing systems, distributed file systems, email forward systems and DRM systems. In this paper, we introduced a new notion of proxy broadcast re-encryption (PBRE). In a PBRE scheme, a delegator, Alice, can delegate the decryption right to a set of users at a time, which means that Alice’s ciphertext can be broadcast re-encrypted. We propose a PBRE scheme and prove its security against a chosen-ciphertext attack (CCA) in the random oracle model under the decisional n-BDHE assumption. Furthermore, our scheme is collusion-resistant, which means the proxy cannot collude with a set of delegates to reveal the delegator’s private key.

Dynamic Encrypted Data Sharing Scheme Based on Conditional Proxy Broadcast Re-Encryption for Cloud Storage

Since Cloud Service Provider is a semi-trusted party in cloud storage, to protect data from being disclosed, users’ data are encrypted before being uploaded to a cloud server. Undoubtedly, flexible encrypted data sharing is a very important demand required by cloud storage users, whereas few schemes have being designed to satisfy this demand. In this paper, based on conditional proxy broadcast re-encryption technology, an encrypted data sharing scheme for secure cloud storage is proposed. The scheme not only achieves broadcast data sharing by taking advantage of broadcast encryption, but also achieves dynamic sharing that enables adding a user to and removing a user from sharing groups dynamically without the need to change encryption public keys. Moreover, by using proxy re-encryption technology, our scheme enables the proxy (cloud server) to directly share encrypted data to the target users without the intervention of data owner while keeping data privacy, so that greatly improves the sharing performance. Meanwhile, the correctness and the security are proved; the performance is analyzed, and the experimental results are shown to verify the feasibility and the efficiency of the proposed scheme.

Chosen-ciphertext secure bidirectional proxy broadcast re-encryption schemes

A proxy re-encryption PRE scheme supports the delegation of decryption rights via a proxy, who makes the ciphertexts decryptable by the delegatee. However, how to structure a chosen-ciphertext secure proxy re-encryption scheme without pair is still an open question. In this paper, by adjusting the Schnorr signature scheme and giving the accessional ciphertext components, a bidirectional which the proxy is able to transform ciphertexts in both directions proxy broadcast re-encryption schemes PBRE was proposed without pair, and the reduction of scheme's security is the computational Diffie-Hellman CDH assumption. The proof of security shows that the proposed scheme is chosen-ciphertext attack secure in the random oracle model.

Chosen-ciphertext secure bidirectional proxy broadcast re-encryption schemes

A proxy re-encryption PRE scheme supports the delegation of decryption rights via a proxy, who makes the ciphertexts decryptable by the delegatee. However, how to structure a chosen-ciphertext secu...

Analysis and Improvements of Several (H)IBS/IBSC/PRBE Schemes

Constructing efficient (Hierarchical) identitybased signature/signcryption ((H)IBS/IBSC) schemes in thestandard model with full security remain as open problemsfor a long time. Ren et al. constructed efficient (H)IBS/IBSCschemes with full security without random oracle in ISDPE’07 and Chinacrypt’08, . They claimed their schemescan be proved to simultaneously achieve high efficiency,short public parameters and a tight reduction. But weshall show their schemes are not secure. Furthermore, wegive improvements to these schemes which can resist theproposed attack. Proxy re-encryption is a primitive whichallows the transformation from A’s ciphertext to be B’sciphertext by using proxies, without the proxy knowing thecorresponding plaintexts or secret keys of A or B. Proxybroadcast re-encryption aims at transforming ciphertextfrom one user to a group, which is a generalization of proxyre-encryption. Recently, Sun et al. proposed a CCA-secureunidirectional proxy broadcast re-encryption in the standardmodel, we also show their scheme has some flaws.