Delegation Of Decryption Rights Research Articles

Collusion-resistant identity-based Proxy Re-encryption: Lattice-based constructions in Standard Model

The concept of proxy re-encryption (PRE) dates back to the work of Blaze, Bleumer, and Strauss in 1998. PRE offers delegation of decryption rights, i.e., it securely enables the re-encryption of ciphertexts from one key to another, without relying on trusted parties. PRE allows a semi-trusted third party termed as a “proxy” to securely divert encrypted files of user A (delegator) to user B (delegatee) without revealing any information about the underlying files to the proxy. To eliminate the necessity of having a costly certificate verification process, Green and Ateniese introduced an identity-based PRE (IB-PRE). The potential applicability of IB-PRE sprung up a long line of intensive research from its first instantiation. Unfortunately, till today, there is no collusion-resistant unidirectional IB-PRE secure in the standard model, which can withstand quantum attack. In this paper, we present the first concrete constructions of collusion-resistant unidirectional IB-PRE, for both selective and adaptive identity, which are secure in standard model based on the hardness of learning with errors problem.

Proxy re-encryption for fine-grained access control: Its applicability, security under stronger notions and performance

Proxy Re-encryption (PRE) offers an efficient solution for enforcing access control on outsourced data through delegation of decryption rights of a delegator to a delegatee. However, to meet practical security requirements of an access control model, the delegator must control these delegations such that a re-encryption key enables the delegation of decryption rights of only a subset of the delegator’s ciphertexts. In this paper, we focus on a category of PRE-based primitives, which we refer to as “PRE with controlled delegation”. In these primitives, instead of the re-encryption key alone, the re-encryption key and authorization of the delegatee for a data item collectively determine whether the ciphertext transformation results in a valid re-encrypted ciphertext under the delegatee’s public key. This paper provides an exhaustive functional, security and performance analysis of all the existing schemes for PRE with controlled delegation in a concrete fine-grained access control model. We show that the traditional PRE security notions are insufficient to address all the security aspects of the access control model. Motivated by our analysis, we formulate stronger security notions and state the desirable efficiency requirements for PRE schemes applicable in the concrete fine-grained access control model. We show the validity of the proposed security notions by formally proving the insecurity of a conventional PRE scheme and security of one of the PRE schemes with controlled delegation under the proposed stronger PRE security notions. We critically analyze all schemes for PRE with controlled delegation under the proposed stronger security notions and with respect to the efficiency requirements. We show that no scheme for PRE with controlled delegation simultaneously satisfies the efficiency and security requirements formulated in this paper. Finally, we present possible future research directions to obtain a PRE-based solution that is secure under the proposed stronger security notions and satisfies all desirable performance requirements in a fine-grained access control model.

Delegation of Decryption Rights With Revocability From Learning With Errors

The notion of decryption rights delegation was initially introduced by Blaze et al. in EUROCRYPT 1998. It, defined as proxy re-encryption , allows a semi-trusted proxy to convert a ciphertext intended for a party to another ciphertext of the same plaintext, without knowledge of the underlying plaintext and decryption key. It has been explored to many real-world applications, e.g., encrypted email forwarding. However, the intrinsic all-or-nothing share feature of proxy re-encryption yields a limitation that the share cannot be revoked. This may hinder the scalability of its applications in practice. In this paper, for the first time, we define the concept of revocability in terms of decryption rights delegation. The novel concept enables data owner to revoke the shared decryption rights when needed. Inspired by the seminal lattice-based proxy re-encryption proposed in PKC 2014, we design a concrete lattice-based construction which satisfies the notion. In our construction, we make use of binary-tree structure to implement the revocation of decryption rights, so that the update of re-encryption key is reduced to $O(logN)$ (instead of $O(N)$ ), where $N$ is the maximum number of delegatee. Furthermore, the security of our scheme is based on the standard learning with errors problem (LWE problem), which could be reduced to the worst-case hard problems (such as GapSVP and SIVP) in the context of lattices. The scheme is chosen ciphertext secure in the standard model. As of independent interest, our scheme achieves both backward and forward security, which means that once a user is revoked after a time period $\mathbf {t}$ , it cannot gain access to all encrypted files before and after $\mathbf {t}$ .

Provably secure key-aggregate cryptosystems with auxiliary inputs for data sharing on the cloud

In the applications of Internet of Things (IoT), users usually do not believe that the cloud server is doing a good job of confidentiality, and thus the private data/documents are encrypted and maintained in the cloud storage. And then, fine-grained data sharing of these encrypted data for increased efficiency is an important requirement. Key-aggregate cryptosystem (KAC) has been proposed to address this problem, which can realize efficient delegation of decryption rights of any subset of ciphertexts. However, the end-devices of IoT may not have the special trusted hardware, and the stored keys are apt to be leaked by side-channel attacks. To solve this problem, we design two leakage-resilient KAC schemes, which can be proved secure with auxiliary input. We also implement these schemes over two platforms to test their applicability for the resource-constrained devices.

Key-aggregate authentication cryptosystem for data sharing in dynamic cloud storage

Sharing encrypted data with different users via public cloud storage is an important functionality. Therefore, we propose a key-aggregate authentication cryptosystem that can generate a constant-size key that supports flexible delegation of decryption rights for any set of ciphertexts. The size of the key is independent of the number of maximum ciphertexts, meaning that the expense of our scheme is stable no matter how frequently users upload files to the cloud server. In addition, the authentication process in our scheme solves the key-leakage problem of data sharing. The data owner can extract an aggregated key that includes indices of the ciphertexts, the identity of the delegate, and the expiration date of the key. The key with the public parameters is used by the cloud server to identity the person or entity requesting a download, allowing the cloud server to control the right to download. Remarkably, we proved that the authentication key cannot be forged, and the message in this key cannot be denied. The method that is used to achieve efficient and secure data sharing in dynamic cloud storage must be stable in expense and leakage-resilient. Our scheme simultaneously satisfies both of these requirements.

An Efficient System for Scalable Data Sharing In Cloud Storage

Using the cloud storage, users store their data on the cloud without the burden of data storage and maintenance and services and high-quality applications from a shared pool of configurable computing resources. Cryptography is probably the most important aspect of communications security and is becoming increasingly important as a basic building block for computer security. As data sharing is an important functionality in cloud storage, In this paper we show that how to securely, efficiently and flexibly share data with others in cloud storage, Cloud-validation based Flexible Distributed, Migration, ciphertext with aggregate key encryption for data stored in cloud. This scheme provides secure data storage and retrieval. Along with the security the access policy is also hidden for hiding the user’s identity. This scheme is so powerful since we use aggregate encryption and string matching algorithms in a single scheme. The scheme detects any change made to the original file and if found clear the error’s. The algorithm used here are very simple so that large number of data can be stored in cloud without any problems. The security, authentication, confidentiality are comparable to the centralized approaches. A set of constant-size cipher texts such that efficient delegation of decryption rights for any set of cipher texts is possible the best. Index Terms String matching algorithms, Cloud-validation based Flexible Distributed, Migration, and cipher text.

A Review on Key-Aggregate Cryptosystem for Climbable Knowledge Sharing in Cloud Storage

The Data sharing is an important functionality in cloud storage. In this article, we show how to securely, efficiently, and flexibly share data with others in cloud storage. We describe new public-key cryptosystems which produce constant-size ciphertexts such that efficient delegation of decryption rights for any set of ciphertexts are possible. The novelty is that one can aggregate any set of secret keys and make them as compact as a single key, but encompassing the power of all the keys being aggregated. In other words, the secret key holder can release a constant-size aggregate key for flexible choices of ciphertext set in cloud storage, but the other encrypted files outside the set remain confidential. This compact aggregate key can be conveniently sent to others or be stored in a smart card with very limited secure storage. We provide formal security analysis of our schemes in the standard model. We also describe other application of our schemes. In particular, our schemes give the first public-key patient controlled encryption for flexible hierarchy, which was yet to be known.

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...

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.

Key-Aggregate Cryptosystem for Scalable Data Sharing in Cloud Storage

Data sharing is an important functionality in cloud storage. In this paper, we show how to securely, efficiently, and flexibly share data with others in cloud storage. We describe new public-key cryptosystems that produce constant-size ciphertexts such that efficient delegation of decryption rights for any set of ciphertexts are possible. The novelty is that one can aggregate any set of secret keys and make them as compact as a single key, but encompassing the power of all the keys being aggregated. In other words, the secret key holder can release a constant-size aggregate key for flexible choices of ciphertext set in cloud storage, but the other encrypted files outside the set remain confidential. This compact aggregate key can be conveniently sent to others or be stored in a smart card with very limited secure storage. We provide formal security analysis of our schemes in the standard model. We also describe other application of our schemes. In particular, our schemes give the first public-key patient-controlled encryption for flexible hierarchy, which was yet to be known.