Chosen-ciphertext Research Articles

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.

Sparse phase information for secure optical double-image encryption and authentication

A novel optical encryption and authentication method by sparse phase information was proposed. Phase-only component of double-image encryption function was generated and considered for sparse strategy. Partial information of these phase values was subjected to the authentication process. The sparse strategy of the phase data permits simultaneous data reduction to achieve the general requirements of storage and transmission. Cryptanalysis of the proposed method was carried out in terms of chosen-plaintext and chosen-ciphertext attacks. The sparse strategy for phase data makes it difficult to recognize the confidential information shown by double-image encryption and authentication system, thus, the security level of the overall process was increased. Computational simulations displayed the feasibility and more security of the proposed method.

IBEET-RSA: Identity-Based Encryption with Equality Test over RSA for Wireless Body Area Networks

Wireless body area network (WBAN) constitutes a widely implemented technique for remote acquisition and monitoring of patient health-related information via the use of embodied sensors. Given that security and privacy protection, including, but not limited to user authentication, integrity, and confidentiality, are both key challenges and a matter of deep concern when it comes to the deployment of emerging technologies in healthcare applications, state-of-the-art measures and solutions are needed to fully address security and privacy concerns in an effective and sensible manner by considering all the benefits and limitation of remote healthcare systems. In this paper, we proposed an efficient and secure identity-based encryption scheme under the RSA assumption providing equality test. We then proved the security of our scheme for one-way secure against chosen-identity and chosen-ciphertext attacks (OW-ID-CCA) by means of the random oracle model. The performance evaluation results indicated that our scheme outperforms other security schemes in terms of providing relatively low computational cost and stable compatibility with WBAN applications.

Flexible, Efficient, and Secure Access Delegation in Cloud Computing

The convenience of the cloud-assisted Internet of Things has led to the need for improved protections for the large volumes of data collected from devices around the world and stored on cloud-based servers. Proxy re-encryption (PRE) has been presented as a suitable mechanism for secure transmission and sharing of files within the cloud. However, existing PRE schemes do not support unidirectional data transformation, fine-grained controls, multiple hops, and identity-based encryption simultaneously. To solve these problems, we propose a unidirectional multi-hop identity based-conditional PRE scheme that meets all of the above requirements. Our proposal has the additional benefits of a constant ciphertext size, non-interactivity, and collusion resistance. We also prove that our scheme is secure against adaptive identity chosen-ciphertext attacks in the standard model.

Adaptively Secure Anonymous Identity-based Broadcast Encryption for Data Access Control in Cloud Storage Service

Cloud computing is now a widespread and economical option when data owners need to outsource or share their data. Designing secure and efficient data access control mechanism is one of the most challenging issues in cloud storage service. Anonymous broadcast encryption is a promising solution for its advantages in the respects of computation cost and communication overload. We bring forward an efficient anonymous identity-based broadcast encryption construction combined its application to the data access control mechanism in cloud storage service. The lengths for public parameters, user private key and ciphertext in the proposed scheme are all constant. Compared with the existing schemes, in terms of encrypting and decrypting computation cost, the construction of our scheme is more efficient. Furthermore, the proposed scheme is proved to achieve adaptive security against chosen-ciphertext attack adversaries in the standard model. Therefore, the proposed scheme is feasible for the system of data access control in cloud storage service.

CCA-Secure Deterministic Identity-Based Encryption Scheme

Deterministic public-key encryption, encrypting a plaintext into a unique ciphertext without involving any randomness, was introduced by Bellare, Boldyreva, and O'Neill (CRYPTO 2007) as a realistic alternative to some inherent drawbacks in randomized public-key encryption. Bellare, Kiltz, Peikert and Waters (EUROCRYPT 2012) bring deterministic public-key encryption to the identity-based setting, and propose deterministic identity-based encryption scheme (DIBE). Although the construc- tions of chosen plaintext attack (CPA) secure DIBE scheme have been studied intensively, the construction of chosen ciphertext attack (CCA) secure DIBE scheme is still challenging problems. In this paper, we introduce the notion of identity-based all-but-one trapdoor functions (IB-ABO-TDF), which is an extension version of all-but-one lossy trapdoor function in the public-key setting. We give a instantiation of IB-ABO-TDF under decisional linear assumption. Based on an identity-based lossy trapdoor function and our IB-ABO-TDF, we present a generic construction of CCA-secure DIBE scheme.

Re-Keying Scheme Revisited: Security Model and Instantiations

The re-keying scheme is a variant of the symmetric encryption scheme where a sender (respectively, receiver) encrypts (respectively, decrypts) plaintext with a temporal session key derived from a master secret key and publicly-shared randomness. It is one of the system-level countermeasures against the side channel attacks (SCAs), which make attackers unable to collect enough power consumption traces for their analyses by updating the randomness (i.e., session key) frequently. In 2015, Dobraunig et al. proposed two kinds of re-keying schemes. The first one is a scheme without the beyond birthday security, which fixes the security vulnerability of the previous re-keying scheme of Medwed et al. Their second scheme is an abstract scheme with the beyond birthday security, which, as a black-box, consists of two functions; a re-keying function to generate a session key and a tweakable block cipher to encrypt plaintext. They assumed that the tweakable block cipher was ideal (namely, secure against the related key, chosen plaintext, and chosen ciphertext attacks) and proved the security of their scheme as a secure tweakable block cipher. In this paper, we revisit the re-keying scheme. The previous works did not discuss security in considering the SCA well. They just considered that the re-keying scheme was SCA resistant when the temporal session key was always refreshed with randomness. In this paper, we point out that such a discussion is insufficient by showing a concrete attack. We then introduce the definition of an SCA-resistant re-keying scheme, which captures the security against such an attack. We also give concrete schemes and discuss their security and applications.

Breaking an Image Encryption Algorithm Based on DNA Encoding and Spatiotemporal Chaos.

Recently, an image encryption algorithm based on DNA encoding and spatiotemporal chaos (IEA-DESC) was proposed. In IEA-DESC, pixel diffusion, DNA encoding, DNA-base permutation and DNA decoding are performed successively to generate cipher-images from the plain-images. Some security analyses and simulation results are given to prove that it can withstand various common attacks. However, in this paper, it is found that IEA-DESC has some inherent security defects as follows: (1) the pixel diffusion is invalid for attackers from the perspective of cryptanalysis; (2) the combination of DNA encoding and DNA decoding is equivalent to bitwise complement; (3) the DNA-base permutation is actually a fixed position shuffling operation for quaternary elements, which has been proved to be insecure. In summary, IEA-DESC is essentially a combination of a fixed DNA-base position permutation and bitwise complement. Therefore, IEA-DESC can be equivalently represented as simplified form, and its security solely depends on the equivalent secret key. So the equivalent secret key of IEA-DESC can be recovered using chosen-plaintext attack and chosen-ciphertext attack, respectively. Theoretical analysis and experimental results show that the two attack methods are both effective and efficient.

A novel fast image encryption algorithm for embedded systems

Nowadays, embedded systems can be found everywhere in daily life. In the development of embedded systems, data security is one of the critical factors. Encryption is an effective way to protect data from threats. Among encryption algorithms, chaos-based methods have strong cryptographic properties since chaotic systems are sensitive to initial conditions and parameters. However, most of these algorithms cannot be applied in practice because their encryption speed is not fast enough. In this paper, a fast image encryption algorithm is proposed. Compared with traditional chaos-based image encryption algorithms, the proposed method utilizes mixed-sequence and decorrelation operation to enhance the randomness of chaotic sequence. Moreover, it used minimum length of the sequence which is determined by experiments. Therefore, the proposed scheme spends much less computation time, which is an important advantage for being applied in practice. Testing results have shown that this algorithm has good performance in resisting known attacks, such as known-plaintext attacks, chosen ciphertext attacks, statistical attacks, differential attacks, and various brute-force attacks.

Improving the proof of "Privacy-preserving attribute-keyword based data publish-subscribe service on cloud platforms".

Most recently, Kan Yang et al. proposed an attribute-keyword based encryption scheme for data publish-subscribe service(AKPS), which is highly useful for cloud storage scenario. Unfortunately, we discover that there is a flaw in the security proof of indistinguishability of the tag and trapdoor against chosen keyword attack under the Bilinear Diffie-Hellman (BDH) assumption. As the security proof is a key component for a cryptographic scheme, based on the Decisional Diffie-Hellman (DDH) assumption, we improve the security proof method and give a new security proof of the AKPS scheme for indistinguishability of the tag and trapdoor in our proposal, which is more rigorous than the original one. Furthermore, we also demonstrate that the AKPS scheme is secure against data Replayable Chosen Ciphertext Attack (RCCA).

An identity-based encryption technique using subtree for fuzzy user data sharing under cloud computing environment

The advancement of the cloud storage technology opens up a wide range of possibilities for adaptable data sharing. When sharing data to an extensive number of users with fuzzy identities, the data proprietor must use an appropriate identity-based encryption technique that satisfies both efficiency and security prerequisites. Identity-based encryption is a promising possibility to ensure fuzzy user data sharing while meeting the security essentials; however, it may encounter efficiency trouble in multi-receiver settings. Recently, identity-based encryption has received much attention, and most of the research has aimed to apply the technique in real-world systems. A major concern about using identity-based encryption is the safety of the private keys, as disclosure of secret keys requires the reissuing of encryptions already doled out. The capability to minimize the risks associated with key disclosure is particularly important due to the increased use of mobile and unprotected devices. In this article, we shall propose a forward-secure identity-based encryption technique based on subtree for fuzzy user data sharing under cloud computing environment, and we shall demonstrate that the technique is semantically secure against a chosen subtree and chosen ciphertext attack (IND-CST–CCA). In addition, we will show the superiority of our new technique over the currently existing methods in terms of security and the length of public key. Then, we will also discuss the potential of our new technique to be deployed in pay TV systems and grid security.

Cryptanalysis and improvement in a chaotic image cipher using two-round permutation and diffusion

Cryptanalysis is significant for the design of secure image cryptosystem. Recently, a chaotic image encryption scheme using two rounds of Latin square-based permutation and diffusion was proposed. Although two-round encryption is used, the cryptosystem has still been cracked successfully by the combined attack using both chosen-plaintext attack (CPA) and chosen-ciphertext attack due to the inherent flaw that the same key was used in both permutation and diffusion phases of each round. Therefore, different keys are used in each encryption phase of the improved cryptosystem. However, in this paper, we further attacked the two-round encryption with different keys using only CPA. By counting the number of the diffused pixels in the first diffusion phase from the processed encrypted image, the first permutation of one pixel is confirmed, and then the whole equivalent key stream of the first permutation can be obtained by limited CPA. Based on this, the key stream of the third permutation phase is obtained in a similar way. Meanwhile, all the mappings of the fourth diffusion are collected by 256 CPA, and 17 possible mappings in average are selected by verification. Finally, the key stream of the second diffusion is obtained using two pairs of chosen images. Experiments show that the encrypted image can be cracked successfully by the proposed attack. This work is instructive to the cryptanalysis of multi-round encryption. In order to remedy the security weakness, an improved cryptosystem is also proposed, followed by thorough security analysis.

Continuous leakage-resilient identity-based encryption with leakage amplification

In modern computer systems, leakage of private information may cause catastrophic consequences, especially those are related to the secret keys in cryptographic mechanisms. Therefore, it has been widely accepted both in academia and industry that cryptographic schemes should withstand various leakage attacks, including the continuous leakage attacks. Although a lot of researches have been conducted towards this issue and some progresses have been made, there are still many unsolved problems in this area. For example, in the majority of the existing identity-based encryption (IBE) schemes with (continuous) leakage resilience, the upper bound of leakage is required to be fixed. But in many real-world applications, such a requirement is inadequate to protect the schemes against the leakage attacks. Moreover, many previous efforts aiming to build IBE schemes that are secure against the chosen-ciphertext attacks (CCA) need to rely on the q-type assumptions. But these solutions are not desirable, because the q-type assumptions are non-static assumptions. In this paper, in order to address the above mentioned problems, we demonstrate how to construct a continuous leakage-resilient CCA-secure IBE scheme with leakage amplification, in which the leakage parameter has an arbitrary length. The benefit is that the length of permitted leakage in our scheme can be adjusted flexibly according to the leakage requirements. Moreover, the security of our proposed scheme can be proved with static assumptions in the standard model. Compared with the related works in the literature, our scheme enjoys a unique feature that it allows continuous leakage of multiple keys simultaneously, e.g. continuous leakage of the master secret key as well as the user’s private key.

A fair offline electronic cash scheme with multiple-bank in standard model

ABSTRACTOffline electronic cash is a new and well-acknowledged type of e-cash scheme that can release the bank from participating in every spending protocol. However, it is still an unsolved problem to design a secure and efficient fair offline e-cash scheme. Considering this problem, in this paper, we have proposed a fair offline electronic cash scheme with multiple banks in pairing-based instantiation. We adopt Groth–Sahai non-interactive zero-knowledge proof technology in our scheme, to design non-interactive e-cash transactions. Additionally, inspired by Water’s group signature, our solution supports not only multiple users, but also users with accounts in different banks. Moreover, our scheme has efficient double-spending checking and a fair control mechanism. We have formally defined the security properties of the scheme in a standard model, and provided the detailed security proofs of the security properties concerning chosen ciphertext attack (CCA) anonymity, unforgeability and traceability. Analysis and comparison show that our scheme has advantages both in security and in efficiency.

Proxy Re-Encryption in Access Control Framework of Information-Centric Networks

As a novel network architecture, information-centric networking (ICN) has a good performance in facilitating content sharing among users. Although in-network cache used in ICN can effectively solve the problem of network congestion. Meanwhile, it also brings a lot of challenges such as security and privacy issues during data transformation. Some of the current solutions are based on the traditional encryption technology, but these solutions introduce significant overhead in the client side and have a high requirement to the memory and computing power of end user. In this paper, we use an efficient proxy re-encryption (PRE) scheme in ICN framework to help reduce the overhead on the user-side while guaranteeing flexible data sharing between subscribers and even their cooperator. Our proposal has the additional benefits of a non-interactivity and collusion resistance. We also prove that our scheme is secure against adaptive replayable adaptive chosen ciphertext attack (RCCA) in re-encryption and chosen ciphertext attack (CCA) secure in complete ICN encryption. Our analysis of this program also shows that the scheme has a relatively good performance in computation cost and communication complexity aspects.

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.

Improved Lattice-Based Signcryption in the Standard Model

Signcryption is a basic cryptographic primitive that simultaneously captures the functions of encryption and signature. To realize comprehensive information security against quantum computing attacks, lattice-based signcryption schemes have been successively proposed. However, the performance of signcryption schemes should be improved in the lattice setting. An efficient lattice-based signcryption scheme in the standard model is proposed in this paper. Under the ring learning with errors (RLWE) assumption and the ideal short integer solution (ISIS) assumption, the proposed signcryption scheme achieves indistinguishability against adaptive chosen ciphertext attacks (IND-CCA2) and existential unforgeability under an adaptive chosen-message attack (EUF-ACMA). Our scheme not only reduces the communication and computational overhead but also realizes a new design that combines the partitioning technique with the idea of tag-based key encapsulation. The performance analysis results show that our scheme is more efficient than previous lattice-based signcryption schemes in the standard model.

Improved Cryptanalysis of Provable Certificateless Generalized Signcryption

Certificateless generalized signcryption adaptively work as certificateless signcryption, signature or encryption scheme having single algorithm for suitable storage-constrained environments. Recently, Zhou et al. proposed a novel Certificates generalized scheme, and proved its ciphertext indistinguishability under adaptive chosen ciphertext attacks (IND-CCA2) using Gap Bi-linear Diffie-Hellman and Computational Diffie-Hellman assumption as well as proved existential unforgeability against chosen message attacks (EUF-CMA) using the Gap Bi-linear Diffie-Hellman and Computational Diffie-Hellman assumption in random oracle model. In this paper, we analyzed Zhou et al. scheme and unfortunately proved IND-CCA2 insecure in encryption and signcryption modes in defined security model. We also present a practical and improved scheme, provable secure in random oracle model.

Using Transposition Padding to Get CCA2 Security From Any Deterministic Encryption Schemes

We study how to make any deterministic encryption scheme probabilistic and secure against adaptively chosen ciphertext attacks. A new transpositional padding encryption scheme is proposed, with which we construct a universal scheme, namely, a transpositional padding encryption scheme, which has three novel attributes: 1) it can pad a given plaintext into several different values once the randomness is chosen while the previous padding schemes only pad a given plaintext into a fixed value; 2) it introduces the randomness into a ciphertext without employing hash function or random oracle, and; 3) it enables the encrypted message to contain more useful information that may exceed the upper limit of plaintext space. Then, we give this encryption scheme an instantiation of RSA, which is proven to be indistinguishable under adaptively chosen ciphertext attacks without random oracle that assumes a variant of the standard RSA problem. The variant problem is a novel arithmetic problem, and it is weaker than the standard RSA problem.