Conditional Proxy Re-encryption Scheme Research Articles

Attribute-Based Verifiable Conditional Proxy Re-Encryption Scheme.

There are mostly semi-honest agents in cloud computing, so agents may perform unreliable calculations during the actual execution process. In this paper, an attribute-based verifiable conditional proxy re-encryption (AB-VCPRE) scheme using a homomorphic signature is proposed to solve the problem that the current attribute-based conditional proxy re-encryption (AB-CPRE) algorithm cannot detect the illegal behavior of the agent. The scheme implements robustness, that is the re-encryption ciphertext, can be verified by the verification server, showing that the received ciphertext is correctly converted by the agent from the original ciphertext, thus, meaning that illegal activities of agents can be effectively detected. In addition, the article demonstrates the reliability of the constructed AB-VCPRE scheme validation in the standard model, and proves that the scheme satisfies CPA security in the selective security model based on the learning with errors (LWE) assumption.

An Identity-Based Proxy Re-Encryption Scheme With Single-Hop Conditional Delegation and Multi-Hop Ciphertext Evolution for Secure Cloud Data Sharing

Proxy re-encryption (PRE) provides a promising solution for applications requiring efficient and secure ciphertext conversion, such as secure cloud data sharing. While the one with the function of ciphertext evolution is more desirable for some long-term schemes involving key update. Recently, Yao et al. constructed an identity-based conditional proxy re-encryption scheme simultaneously supporting authorization and ciphertext evolution. However, its delegated ciphertext can be re-authorized, which may cause the authorization to exceed the original delegator’s expectation. In contrast, the single-hop PRE authorization scheme may be more appropriate for systems requiring better control over authorization. In this paper, an identity-based proxy re-encryption scheme with single-hop conditional delegation and multi-hop ciphertext evolution (IBPRE-SHCD-MHCE) is proposed. Also, its description, construction, and security analysis are given. The analysis and experimental comparison results show that the proposed scheme has improved the computational efficiency and storage consumption compared with the two underlying schemes.

Efficient and HRA Secure Universal Conditional Proxy Re-Encryption for Cloud-Based Data Sharing

Cloud computing has become popular in data sharing mainly because it has huge storage capacity and computing power. Securing the privacy of sensitive data for cloud-based data sharing is vital. Currently, there are various conditional proxy re-encryption (UPRE) schemes that have been proposed to resolve the privacy issue. Nevertheless, the existing UPRE schemes cannot allow the proxy (e.g., the cloud server) to transfer the outsourced encrypted data under the data owner’s public key of any homomorphic encryption scheme into the encrypted data under the data user’s public key of a homomorphic encryption scheme (possibly different from the data owner). The transformation of outsourced encrypted data between homomorphic encryption schemes is more suitable for the real data sharing in clouds. Consequently, we present the notion of universal conditional proxy re-encryption (UCPRE) to solve the issue of flexible transformation of outsourced encrypted data between homomorphic encryption schemes in cloud-based data sharing. UCPRE is lightweight in the sense that it only requires the re-encrypted key generation and re-encryption algorithms. We give the definition of UCPRE and prove that it is HRA secure without random oracle. Finally, we show that our UCPRE is efficient and rational compared to other existing CPRE schemes by instantiating our UCPRE.

A blockchain-based fine-grained data sharing scheme for e-healthcare system

The cloud-aided sharing of e-healthcare data has great positive significance for research. However, due to the privacy consideration, these data are usually encrypted before uploading to the cloud server which impedes data sharing between different medical institutions. Conditional proxy re-encryption (CPRE) allows the proxy to converse ciphertext, especially by specifying a condition embed in the re-encryption key to achieve fine-grained access control over the ciphertext. Unfortunately, existing CPRE schemes cannot ensure the privacy of the condition, which may contain some sensitive private information. Furthermore, a malicious proxy server may return part of the results and even false data to save its computation or bandwidth. To solve these problems, we propose a blockchain-based condition invisible proxy re-encryption scheme for the e-healthcare system. The proposed scheme guarantees the confidentiality of the data by hiding the condition in the re-encryption key so that the proxy cannot learn anything about the condition. Moreover, the ciphertext-searching algorithm is leveraged by executing the smart contract in the blockchain which ensures the results are correct and complete. Finally, experiment results demonstrate the practicability of the proposed scheme in applications.

A Novel Revocable and Identity-Based Conditional Proxy Re-Encryption Scheme With Ciphertext Evolution for Secure Cloud Data Sharing

Proxy re-encryption (PRE), with the unique ciphertext transformation ability, enables various ciphertext authorization applications to be implemented efficiently. However, most existing PRE schemes mainly focus on access authorization while ignoring the situation where the key needs to be changed and the ciphertext needs to be evolved, making the scheme's practicability and security inadequate. Moreover, the few schemes that simultaneously combine ciphertext authorization, key update, and ciphertext evolution are not satisfactory in terms of security. For solving this problem, based on Xiong et al.'s scheme, this paper proposes an improved revocable and identity-based conditional proxy re-encryption scheme with ciphertext evolution (RIB-CPRE-CE) for secure and efficient cloud data sharing. The proposed scheme inherits the characteristics of multi-use, constant ciphertext length, fine-grained authorization, collision-resistance security, and chosen ciphertext attack (CCA) security from the original method. Also, it supports updating ciphertext to adapt to the new key after changing the identity (key) or achieves authorization revocation by evolving ciphertext. Two new algorithms, URKeyGen and UpReEnc, have been integrated into the original delegation scheme to support ciphertext evolution. The formal definition, security model, concrete construction, and security analysis of RIB-CPRE-CE have been presented. The comparison and analysis show that the proposed scheme is practical and secure. Although it adds a ciphertext evolution function for supporting key update and delegation revocation, its efficiency and security are not reduced. The proposed scheme can also be used in other access authorization systems that need to change the key or revoke the authorization. It has certain practicability and security.

An Efficient Public Auditing Scheme for Cloud Storage with Secure Access Control and Resistance Against DOS Attack by Iniquitous TPA

Cloud storage is a cloud based service which delivers scalable on demand on line storage of data and eliminates the need of maintaining local data centre. Storage of data in cloud brings many advantages such as lower-cost, metered service, scalable and ubiquitous access. However, it also raises concerns to its integrity; to save the storage space cloud service provider may delete some rarely access data. Data privacy is another issue which must be addressed to increase data owner’s trust. To address above issues, many researchers have proposed public auditing schemes to validate the integrity of data using third party auditor. These schemes generate metadata using data files on the owner side and store these metadata on the cloud storage along with the file data, which helps in auditing. These schemes address many concerns which arise due to remote data storage. However, computation cost involved for metadata generation at the data owner side is not properly addressed; another issue which is not properly addressed is an iniquitous third party auditor may be the source of denial of service attack by issuing constantly large number of audit request. Our scheme solves these issues by lowering the computation cost at data owner side and controlling the number of times a third party auditor can issue an audit request to the cloud storage. Our Scheme also supports secure access of data using conditional proxy re-encryption scheme and delegation of auditing task by the authorized third party auditor to another auditor for the specified period of times in the case of unavailability of authorized third party auditor.

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.

A New Kind of Conditional Proxy Re-Encryption for Secure Cloud Storage

Secure cloud storage has important applications in our big data-driven society, and to achieve secure cloud storage, we need to enforce strong access control mechanism. Proxy re-encryption (PRE) has been shown to be an effective tool of constructing cryptographically enforced access control schemes. In a traditional PRE scheme, a semi-trusted proxy can convert all ciphertexts for a delegator to ciphertexts for a delegatee once the proxy obtains the relevant re-encryption key from the delegator. In many practical applications, however, a fine-grained delegation of decryption abilities may be demanded, and thus, the notion of conditional PRE (C-PRE) is introduced, which allows only the ciphertexts satisfying a concrete condition to be converted by the proxy. In this paper, we introduce a special kind of C-PRE, sender-specified PRE (SS-PRE), which enables the delegator to delegate the decryption right of the ciphertexts from a specified sender to his/her delegatee. We give a formal definition of SS-PRE and its security model. We also provide the concrete constructions of an IND-CPA secure SS-PRE scheme and an IND-CCA secure SS-PRE scheme with the properties of unidirectionality and single-use and prove the security of both schemes in the standard model. The detailed analysis shows that our new IND-CCA secure SS-PRE scheme achieves a higher efficiency in computation cost and ciphertext size than the conventional C-PRE schemes.

Improved functional proxy re-encryption schemes for secure cloud data sharing

Recently Liang et al. propose an interesting privacy-preserving ciphertext multi-sharing control for big data storage mechanism, which is based on the cryptographic primitive of anonymous multi-hop identity based conditional proxy re-encryption scheme AMH-IBCPRE. They propose a concrete AMH-IBCPRE scheme and conclude their scheme can achieve IND-sCon-sID-CCA secure (indistinguishable secure under selectively conditional selectively identity chosen ciphertext attack). However, our research show their scheme can not be IND-sConsID- CCA secure for single-hop and multi-hop data sharing. Also in 2014, Liang et al. propose an interesting deterministic finite automata-based functional proxy reencryption scheme DFA-based FPRE for secure public cloud data sharing, they also conclude their scheme can achieve IND-CCA secure (indistinguishable secure under chosen ciphertext attack), we also show their scheme can not be IND-CCA secure either. For these two proposals, the main reason of insecurity is that part of the re-encryption key has the same structure as the valid ciphertext, thus the adversary can query on the decryption oracle with this part of the re-encryption key to get secret keys, which will break the CCA-security of their scheme.We give an improved AMH-IBCPRE scheme and an improved DFA-based FPRE scheme for cloud data sharing and show the new schemes can resist our attack and be CCA-secure.We also demonstrate our improved AMH-IBCPRE scheme?s efficiency compared with other related identity based proxy re-encryption schemes, the results show our scheme is almost the most efficient one.

Lattice-Based Identity-Based Homomorphic Conditional Proxy Re-Encryption for Secure Big Data Computing in Cloud Environment

With the arrival of the era of big data, more and more users begin to adopt public cloud storage to store data and compute data. Sharing large amounts of sensitive data in the public cloud will arouse privacy concerns. Data encryption is a widely accepted method to prevent information leakage. How to achieve the cloud sharing and cloud computing of big data is a challenging problem. Conditional proxy re-encryption can solve cloud sharing, and homomorphic encryption can achieve cloud computing. In this paper, we combine conditional proxy re-encryption with homomorphic encryption to construct a lattice-based identity-based homomorphic conditional proxy re-encryption for secure big data computing in cloud environment. The scheme can not only realize the encrypted data sharing in the cloud, but also can realize the encrypted data computing in the cloud. That is, the homomorphic conditional proxy re-encryption scheme can homomorphically evaluate ciphertexts no matter ciphertexts are “fresh” or re-encrypted (re-encrypted ciphertexts can come from different identities). The constructed scheme modifies the homomorphic proxy re-encryption scheme of Ma et al. We also use the approximate eigenvector method to manage the noise level and decrease the decryption complexity without introducing additional assumptions. At last, we prove that the scheme is indistinguishable against chosen-plaintext attacks, key privacy secure and master secret secure.

Special issue on Big Data Security and Intelligent Data in Clouds (BDS‐IDC)

Special issue on Big Data Security and Intelligent Data in Clouds (<scp>BDS‐IDC</scp>)

Identity-based conditional proxy re-encryption with fine grain policy

An identity-based conditional proxy re-encryption scheme (IB-CPRE) allows a semi-trusted proxy to convert a ciphertext satisfying one condition, which is set by the delegator, under one identity to another without the necessity to reveal the underlying message. In ICISC 2012, Liang, Liu, Tan, Wong and Tang proposed an IB-CPRE scheme, and left an open problem on how to construct chosen-ciphertext secure IB-CPRE supporting OR gates on conditions. In this work, we answer this aforementioned problem by constructing an identity-based conditional proxy re-encryption scheme with fine grain policy (IB-CPRE-FG). In an IB-CPRE-FG scheme, each ciphertext is labeled with a set of descriptive conditions and each re-encryption key is associated with an access tree that specifies which type of ciphertexts the proxy can re-encrypt. Furthermore, our scheme can be proved secure against adaptive access tree and adaptive identity chosen-ciphertext attack.

A new outsourcing conditional proxy re‐encryption suitable for mobile cloud environment

SummaryThe mobile cloud is a highly heterogenous and constantly evolving network of numerous portable devices utilizing the powerful back‐end cloud infrastructure to overcome their severe deficiency in computing resource and offer various services such as data sharing. Inherently, in mobile cloud, the risk of user privacy invasion by the cloud operator is high. The conditional proxy re‐encryption (CPRE) is a useful concept for secure group data sharing via cloud while preserving the privacy of the shared data from any unintended third parties including the cloud operator. Unfortunately, the state‐of‐art CPRE is not particularly designed for mobile cloud environment and therefore imposes heavy burdens to the weak mobile cloud clients. This paper introduces a new CPRE scheme, namely the CPRE for mobile cloud, which utilizes the back‐end cloud to the extreme extent so that the overhead of terminals is drastically reduced. Specifically, our scheme outsources a significant amount of computation overhead caused by the following functions at terminals: (a) re‐encryption key generation, (b) condition value change, and (c) decryption, to the cloud. The proposed scheme also allows users to verify the correctness of outsourced computation under refereed delegation of computation model. Our simulation results show CPRE for mobile cloud that outperforms its existing alternatives. Copyright © 2016 John Wiley &amp; Sons, Ltd.

A Searchable Hierarchical Conditional Proxy Re-encryption Scheme for Cloud Storage Services

As cloud technologies thrive, researches in the field of cloud storage have switched their focus from encryption-decryption techniques that help data owners protect their privacy and data confidentiality to the application of searching techniques on encrypted data while maintaining high level security and privacy of outsource data. To begin with, Song et al. offered some practical techniques for searches on encrypted data. After that, Weng et al. presented their conditional proxy re-encryption scheme where the data owner can decide which ciphertext satisfies a certain keyword condition set and then can have the retrieved data re-encrypted by the semi-trusted proxy server. The basic concepts of the above schemes are indeed quite innovative and do lead the way towards the solutions to the major practical cloud storage application problems; however, of all the researches that follow, none has had both searching on encrypted data and conditional proxy re-encryption combined. In this paper, we propose a new scheme for cloud storage services that integrates keyword search with conditional proxy re-encryption. This say, with a newly added keyword or new proxy, the cloud service provider is able to generate a hierarchical key. As far as data security is concerned, our scheme provides proven data owner authentication, re-delegation, and chosen-ciphertext security. The superior performance of the proposed scheme has been established by comparing it with related works, and our security analysis as well as BAN logic correctness check also offered solid proof that the new scheme is both secure and practical.DOI: http://dx.doi.org/10.5755/j01.itc.45.3.13224

On the security of two identity-based conditional proxy re-encryption schemes

Proxy re-encryption allows a semi-trusted proxy with a re-encryption key to convert a delegator's ciphertext into a delegatee's ciphertext, and the semi-trusted proxy cannot learn anything about the underlying plaintext. If a proxy re-encryption scheme is indistinguishable against chosen-ciphertext attacks, its initialized ciphertext should be non-malleable. Otherwise, there might exist an adversary who can break the chosen-ciphertext security of the scheme. Recently, Liang et al. proposed two proxy re-encryption schemes. They claimed that their schemes were chosen-ciphertext secure in the standard model. However, we find that the original ciphertext in their schemes are malleable. Thus, we present some concrete attacks and indicate their schemes fail to achieve chosen-ciphertext security in the standard model.

Cryptanalysis on a Secret-Sharing Based Conditional Proxy Re-Encryption Scheme

Condition proxy re-encryption is a promising security primitive for pervasive data sharing in such settings as cloud-based social networks and collaborations. However, it is challenging to create a secure condition proxy re-encryption scheme that is applicable for circumstances with multiple conditions. Based on secret sharing, Lan et al. proposed a conditional proxy re-encryption scheme that can support "AND" and "OR" gates over multiple conditions, and claimed that the scheme is secure against Chosen-Ciphertext Attack (CCA) in the random oracle model. However, by giving two concrete attacks, we show that their scheme is not CCA secure and even not secure against Chosen-Plaintext Attack (CPA) under their defined security model. Furthermore, we analyze why the scheme cannot satisfy the security mentioned above.

Research on Non-interactive Construction based on Fuzzy Conditional Proxy Re-encryption

In a conditional proxy re-encryption (C-PRE) scheme, a semi-trusted proxy can transform Alice’s ciphertext into Bob’s ciphertext without learning the underlying plaintext, if the ciphertext satisfies a certain condition. To achieve more fine-grained delegation on conditions, Fang, Wang and Ge introduced the notion of fuzzy conditional proxy re-encryption (FC-PRE), whereby the conditions is viewed a set of descriptive

Efficient and Fully CCA Secure Conditional Proxy Re-Encryption from Hierarchical Identity-Based Encryption

A proxy re-encryption (PRE) allows a data owner to delegate the decryption rights of some encrypted data stored on the cloud without revealing the data to an honest-but-curious cloud service provider (i.e. the PRE proxy). Furthermore, the data owner can offload most of the computational operations to the cloud service provider and hence, using PRE for encrypted cloud data sharing can be very effective even for data owners using limited resource devices (e.g. mobile devices). However, PRE schemes only enables data owners to delegate the decryption rights of all their encrypted data. A more practical notion is a conditional PRE (CPRE) that allows us to specify under what condition the decryption of an encrypted data can be delegated, for example, only sharing all the encrypted files under a directory called ‘public’. In this paper, we provide an affirmative result on the long-standing question of building a full chosen-ciphertext attacks (CCA)-secure CPRE system in the standard model and for the first time, we show that a class of Hierarchical Identity-Based Encryption (HIBE) schemes can be transferred to building a CCA-secure CPRE in the standard model. We also list out some concrete HIBE schemes which fall into this class, e.g., Lewko-Waters HIBE. All existing CCA-secure PRE schemes in the standard model are not conditional while all existing CPRE schemes are either not CCA secure or not in the standard model. By instantiating our generic HIBE-based transformation, we show that an efficient and concrete CPRE scheme which is both CCA secure in the standard model and conditional can be built.

Cloud based data sharing with fine-grained proxy re-encryption

Conditional proxy re-encryption (CPRE) enables fine-grained delegation of decryption rights, and has many real-world applications. In this paper, we present a ciphertext-policy attribute based CPRE scheme, together with a formalization of the primitive and its security analysis. We demonstrate the utility of the scheme in a cloud deployment, which achieves fine-grained data sharing. This application implements cloud server-enabled user revocation, offering an alternative yet more efficient solution to the user revocation problem in the context of fine-grained encryption of cloud data. High user-side efficiency is another prominent feature of the application, which makes it possible for users to use resource constrained devices, e.g., mobile phones, to access cloud data. Our evaluations show promising results on the performance of the proposed scheme.

An Identity-Based Conditional Proxy Re-Encryption in Cloud Computing Environments

In this paper, an identity-based conditional proxy re-encryption (PRE) scheme is proposed, where a delegator provides a re-encryption key satisfying one condition to a semi-trusted proxy who can convert a ciphertext encrypted under the delegator’s public key into one that can be decrypted using the delegatee’s private key. We address the identity-based proxy re-encryption scheme, where the delegator and the delegatee request keys from a trusted party known as a key generator center (KGC), who generates private keys for delegator and delegatee based on their identities. Meanwhile, the identity-based conditional proxy re-encryption scheme satisfies the properties of PRE including unidirectionality, non-interactivity and multi-hop. Additionally, the identity-based conditional proxy re-encryption scheme is efficient in terms of both the communication cost and the computing cost, and can realize security secret sharing in cloud computing environments.