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Recently a hybrid secure image encryption scheme based on Julia set and three-dimensional Lorenz chaotic system was suggested. The offered scheme was based on the multiplicative operation carried out by Julia set fractals and bitwise XOR which was implemented by the trajectories obtained from the Lorenz chaotic system. This paper presents the cryptanalysis of the scheme through a chosen-plaintext attack by taking three different chosen images. In this work, a practical chosen-plaintext attack is performed which reveals that the cryptosystem depending on only multiplication and bitwise XOR operation can be effortlessly attacked. The results of the analysis performed on the retrieved image reflect the effectiveness of the chosen-plaintext attack which fruitfully produces the original image.

Inner product functional encryption (IPFE), as a novel cryptographic primitive, can be classified into public-key IPFE (PK-IPFE) and secret-key IPFE (SK-IPFE). PK-IPFE has the following functions: an encryptor generates the ciphertext by encrypting a vector x → , and a decryptor decrypts the ciphertext and obtains the inner product 〈 x → , y → 〉 if it holds the secret key related to vector y → . The general IPFE cannot describe the hierarchical structure. The superior cannot use the general IPFE to issue the delegating keys for the subordinates, which complicates key management. We first propose a new primitive, hierarchical identity-based PK-IPFE (HID-PK-IPFE). HID-PK-IPFE has the following features. First, the identity of the decryptor can be specified when encrypting. Second, the identity of the recipient has a hierarchical structure. In the hierarchical tree, the upper-level users can generate the private key of the lower-level users; that is, our scheme has a delegation function. We formalize the selective chosen plaintext attack model of HID-PK-IPFE, propose the scheme in the standard model, and prove the security of the scheme on the basis of d-DBDHE assumption. We conducted two sets of simulations. We set the maximum depth of the identity hierarchy to 10, and increased the vector length from 10 to 15. We then listed the time spent by each algorithm in these two ranges. The simulation results show that the running time of each algorithm of our HID-PK-IPFE is completely acceptable in actual application scenarios.

Multimedia data encryption is an ever-growing and challenging domain in the emerging digital world, with image encryption at the forefront to provide privacy for the user’s data. Image encryption aims to generate a stable noisy image irrespective of the input image. The current solution to this communication challenge is to use complex mathematics with a series of algorithms known as public-key cryptography. But the increasing power of computers and the ingenuity of hackers is open up more and more cracks in this mathematical armor. An ideal solution to this problem would provide provable information security, guaranteeing the safety of our personal information. In addition to it, the system must adapt itself to day to day miracles of the real world. Neural assisted techniques are the solutions to satisfy the above-said requirements. Hence, this paper proposes Hopfield neural attractor-assisted image encryption scheme in which combined tent maps are employed for the substitution process. Nowadays, a chosen-plaintext attack is a big challenge for encryption schemes. To resist the chosen plaintext attack, this scheme proposes the higher bitplane confusion using the tent map, which replaces the conventional diffusion process. Besides, the proposed scheme offers desire metrics such as the average correlation of 0.003, entropy as 7.99, and keyspace of 10184.

Hamming quasi-cyclic (HQC) cryptosystem, proposed by Aguilar Melchor et al. , is a code-based key encapsulation mechanism (KEM) submitted for the NIST standardisation process of post-quantum cryptography (PQC). Under the assumption that the s -decision quasi-cyclic syndrome decoding ( s -DQCSD) problem is hard for s = 2 and 3, HQC, viewed as a public-key encryption scheme, is proven to be indistinguishability under chosen plaintext attack (IND-CPA) secure, and can be transformed into an IND-Adaptive chosen ciphertext attack secure KEM. However, the authors will show that the s -DQCSD problem is actually not intractable and HQC cannot attain IND-CPA security with all the proposed parameter sets. As HQC was selected as one of the second-round candidates by NIST, it was also updated to resist attack. The underlying s -DQCSD problem was replaced by the s -DQCSD with a parity problem and they claimed that the updated HQC could attain IND-CPA security under the hardness of the new problem. However, they find that there is some flaw in their security proof and the updated HQC is still vulnerable to attack. To fix it, they define a new problem called s -DQCSD with variable weight and present revised scheme HQC- β , which finally attains the IND-CPA security under the hardness assumption of the new problem.

Range query is an important data search technique in cloud-based electronic healthcare (eHealth) systems. It enables authorized doctors to retrieve target electronic health records (EHRs) that are generated and outsourced by patients from the cloud server. In reality, patients always encrypt their EHRs before outsourcing, making the range query impossible. In this paper, we identify three threats in real cloud-based eHealth systems, i.e., privacy leakage, frequency analysis, and identical data inference. To capture the security properties that resist these threats, we define a security notion of indistinguishability under multi-source ordered chosen plaintext attack (IND-MSOCPA). Then, we propose a multi-source order-preserving encryption (MSOPE) scheme for cloud-based eHealth systems to enable range queries over encrypted EHRs from multiple patients. Security analysis proves that the MSOPE scheme is IND-MSOCPA secure. We also conduct comprehensive performance evaluations, which demonstrate the high efficiency of the MSOPE scheme.

Public key encryption with keyword search (PEKS) allows a cloud server to retrieve particular ciphertexts without leaking the contents of the searched ciphertexts. This kind of cryptographic primitive gives users a special way to retrieve the encrypted documents they need while preserving privacy. Nevertheless, most existing PEKS schemes only offer single-keyword search or conjunctive-keyword searcha. The poorly expressive ability and constantly inaccurate search results make them hard to meet users' requirements. Although several expressive PEKS (EPEKS) schemes were proposed, they entail high computation and communication costs. An ideal EPEKS scheme should enable fast and accurate ciphertext retrieval, while lowering the storage server's load and reducing the amount of communication data. Drawing on the strongly expressive ability of key-policy attribute-based encryption (KP-ABE), we propose a generic construction of EPEKS from KP-ABE. We demonstrate that the derived EPEKS scheme is secure under the chosen keyword attack if the implicit KP-ABE scheme fulfills the anonymity under the chosen plaintext attack. Furthermore, we present a concrete EPEKS scheme over the prime-order groups. The comparison and experimental results indicate that our scheme is more efficient than the existing EPEKS schemes.

In this paper, we study the security of a compressed sensing (CS) based cryptosystem called a sparse one-time sensing (S-OTS) cryptosystem, which encrypts a plaintext with a sparse measurement matrix. To construct the secret matrix and renew it at each encryption, a bipolar keystream and a random permutation pattern are employed as cryptographic primitives, which can be obtained by a keystream generator of stream ciphers. With a small number of nonzero elements in the measurement matrix, the S-OTS cryptosystem achieves efficient CS encryption in terms of memory and computational cost. In security analysis, we show that the S-OTS cryptosystem can be indistinguishable as long as each plaintext has constant energy, which formalizes computational security against ciphertext only attacks (COA). In addition, we consider a chosen plaintext attack (CPA) against the S-OTS cryptosystem, which consists of two sequential stages, keystream and key recovery attacks. Against keystream recovery under CPA, we demonstrate that the S-OTS cryptosystem can be secure with overwhelmingly high probability, as an adversary needs to distinguish a prohibitively large number of candidate keystreams. Finally, we conduct an information-theoretic analysis to show that the S-OTS cryptosystem can be resistant against key recovery under CPA by guaranteeing that the probability of success is extremely low. In conclusion, the S-OTS cryptosystem can be computationally secure against COA and the two-stage CPA, while providing efficiency in CS encryption.

Attribute-based encryption (ABE) scheme has become an important technology in cryptography. However, the considerable overhead of encryption and decryption restricts its application on the devices with limited resource. Fortunately, as the development of cloud computing, someone presents that outsourcing decryption and encryption can be used to deal with the problem. This idea has drawn a lot of attention after being proposed. Recently, Li et al. put forward an efficient verifiable outsourced ABE scheme which outsources the encryption and decryption to the cloud server and enables its valid receivers to verify the correctness of the message after decrypting. However, in this paper, we prove that their scheme is not secure under chosen plaintext attack which is the basic security requirement of ABE scheme. Then, we improve their scheme and illustrate that the improved scheme is adaptive chosen ciphertext attack (CCA2) secure in the random oracle model. The final comparison shows that we do not add extra computational burden to improve the security.

Lattice-based Attribute-based encryption is a well-known cryptographic mechanism that can resist quantum attacks and has the ability of fine-grained access control, and it has a wide range of application scenarios in current Internet of Thing (IoT) era. However, lack of efficiency and existing the problem of large ciphertext expansion rate are the main disadvantages impede the applications of this mechanism. Thus, we propose an efficient and practical ciphertext policy attribute-based encryption (CP-ABE) scheme from lattices in the paper. In this scheme, to make the secret key reusable, we adjust access tree and propose a basic access tree structure, which can be converted from disjunctive normal form, and combine it with a light post-quantum scheme of Kyber. In addition, the compression method and plaintext expansion method are introduced to optimize the scheme. Our CP-ABE scheme is secure against chosen plaintext attack under the hardness of module learning with errors problem. We implement our scheme and compare it with three recent related schemes in terms of security, function and communication cost. Experiments and comparisons show that our CP-ABE scheme has advantages in high encryption efficiency, small matrix dimension, small key sizes, and low ciphertext expansion rate, which has some merit in practice.

This paper studies privacy preserving query services for strong simulation queries in the database outsourcing paradigm. In such a paradigm, clients send their queries to a third-party service provider (SP), who has the outsourced large graph data, and the SP computes the query answers. However, as SP may not always be trusted, the sensitive information of the clients’ queries, importantly, the query structures, should be protected. Moreover, graph pattern queries often have high complexities, whereas data graphs can be large. This paper adopts strong simulation as a practical query semantic for this paradigm. Under this semantic, queries are matched with a notion of balls, which are subgraphs related to the query diameter. We transform the core of the existing strong simulation algorithm using data-oblivious operations (ObSSA) and propose its secure version. We show that the algorithm may encounter an overflow problem even partially homomorphic encryption (PHE) has been used. We then propose an efficient inexact algorithm EncSSA, which is secure under chosen plaintext attack (CPA). The results of privacy analysis are presented. We have conducted experiments on Twitter and Citeseer datasets, and the results show that EncSSA is both efficient and effective.

Over the years, a lot of studied have been conducted on Order Preserving Encryption (OPE) schemes because of its possible application to database design. Unfortunately, few schemes have been able to attain verifiable security and leaks the minimum amount of information possible. Until Popa et al. (2013), no OPE scheme achieved Indistinguishability under an Order Chosen Plaintext Attack (IND-OCPA) security. However, even Popa et al.’s. design potentially leaks the distribution of repeated plaintext values based on ciphertexts. This paper presents encryption scheme, Order Preserving Distribution Scheme (OPDS) which is secure and do not leakages the distribution of repeated plaintext value based on ciphertexts. We modify the mOPE algorithm by adding a security layer, we introduce the security protocol Indistinguishability under an Order Chosen Repeated Plaintext Distribution Attack (INDOCRPDA) which is equivalent to Popa IND-OCPA security, and proof that OPDS is secure. Finally, we provide experimental results on the effectiveness of OPDS scheme in practice.

An encryption scheme is called indistinguishable under chosen plaintext attack (short IND-CPA) if an attacker cannot distinguish the encryptions of two messages of his choice. There are other variants of this definition but they all turn out to be equivalent in the classical case. In this paper, we give a comprehensive overview of these different variants of IND-CPA for symmetric encryption schemes in the quantum setting. We investigate the relationships between these notions and prove various equivalences, implications, non-equivalences, and non-implications between these variants.

Identity-based encryption (IBE), and its hierarchical extension (HIBE), are interesting cryptographic primitives that aim at the implicit authentication on the users&rsquo, public keys by using users&rsquo, identities directly. During the past several decades, numerous elegant pairing-based (H)IBE schemes were proposed. However, most pairing-related security assumptions suffer from known quantum algorithmic attacks. Therefore, the construction of lattice-based (H)IBE became one of the hot directions in recent years. In the setting of most existing lattice-based (H)IBE schemes, each bit of a user&rsquo, s identity is always associated with a parameter matrix. This always leads to drastic but unfavorable increases in the sizes of the system public parameters. To overcome this issue, we propose a flexible trade-off mechanism between the size of the public parameters and the involved computational cost using the blocking technique. More specifically, we divide an identity into l&prime, segments and associate each segment with a matrix, while increasing the lattice modulo slightly for maintaining the same security level. As a result, for the setting of 160-bit identities, we show that the size of the public parameters can be reduced by almost 89.7% (resp. 93.8%) while increasing the computational cost by merely 5.2% (resp. 12.25%) when l&prime, is a set of 16 (resp. 8). Finally, our IBE scheme is extended to an HIBE scheme, and both of them are proved to achieve the indistinguishability of ciphertexts against adaptively chosen identity and chosen plaintext attack (IND-ID-CPA) in the standard model, assuming that the well-known ring learning with error (RLWE) problem over the involved ideal lattices is intractable, even in the post-quantum era.

In recent years, many scholars have been committed to improving the security and practicability of chaotic image encryption. In addition, their proposed schemes mainly focus on two aspects, new or improved chaotic systems and new or improved encryption processes. However, according to cryptanalysis works of scholars, encryption processes of chaotic image encryption schemes deserve more attentions. In this paper, a recently reported chaotic image encryption scheme named the 2D logistic-adjusted-sine-map-based image encryption scheme is comprehensively investigated, and some security, practicability, and rationality problems are found. Therefore, we first point out these problems existing in the reported encryption scheme and make some improvements in practicability and rationality. Next, under the conditions of chosen plaintext attack, we cryptanalyze it and propose a corresponding attack algorithm. For our attack algorithm, simulation test results show that it can completely recover plain images without knowing any secret key related information. Finally, we also present some possible improvements for the security problems of chaotic image encryption scheme under study.

Recently, a color image encryption using combination of the 1D chaotic map has been proposed by Pak et al. The encryption scheme has defined the new chaotic system structure, combined two Sine maps in the permutation stage, and utilized the key-streams generated by the Sine-Sine-map to confuse the permuted image. Then, linear transformation has been employed to permute the diffused image to obtain the encrypted image. However, by using Chosen-plaintext attack, we have found that the encrypted image can be completely cracked and this scheme is not applicable to secure communications. In this paper, the defects of the original algorithm have been analyzed and a Chosen plaintext attack has been proposed to crack the scheme. In addition, we propose an improved algorithm to overcome the defects in the above original algorithm. Experimental results show that the improved scheme can not only maintain the merits of the original one, but also resist the attacks.

Quantum public key encryption system provides information confidentiality using quantum mechanics. This paper presents a quantum public key cryptosystem (QPKC) based on the Bell states. By Holevo’s theorem, the presented scheme provides the security of the secret key using one-wayness during the QPKC. While the QPKC scheme is information theoretic security under chosen plaintext attack (CPA). Finally some important features of presented QPKC scheme can be compared with other QPKC scheme.

Recently, an image encryption based on three-dimensional bit matrix permutation (TDBMP) has been proposed by Zhang et al. The encryption scheme has combined Chen chaotic system with a 3D Cat map in the permutation stage, and defined a new mapping rule (double random position permutation) and utilized key-streams generated by Logistic map to confuse the permuted image. However, we have found that this scheme is vulnerable to chosen plaintext attack and is not applicable to secure communications. In this paper, the shortcomings of TDBMP have been analysed and a chosen plaintext attack has been proposed to break the scheme. After that, we propose an enhanced algorithm to overcome the presented shortcomings in the above original scheme. Experimental results also illustrate that the enhanced scheme not only maintains the merits of the original one, but also has better cryptographic performances in key space, plaintext sensitivity, statistical characteristics, robustness against cropping attack and execution speed, and can therefore effectively ensure a secure image communication.

In recent years, hybrid chaotic image encryption schemes combined with the DNA encryption technology or other technologies have become a research focus of many researchers. However, some researchers neglect security analyses of proposed schemes under the chosen plaintext attack, therefore leaving security vulnerabilities. Considering this situation, we carefully investigate a recently reported hyper-chaotic image encryption scheme using the DNA encryption technology. In this paper, we first point out some issues identified in the reported scheme and make some necessary improvements, and then cryptanalyze it and propose a chosen plaintext attack algorithm. With the proposed attack algorithm, theoretical analyses and test results show that it can completely recover plain images without knowing any secure key related information. Finally, some suggestions for improving the security and practicability of the reported hyper-chaotic image encryption scheme are presented.

Compressive sensing based encryption achieves simultaneous compression-encryption by utilizing a low complex sampling process, which is computationally secure. In this paper, a new novel 1D–chaotic map is proposed that is used to construct an incoherence rotated chaotic measurement matrix. The chaotic property of the proposed map is experimentally analysed. The linear measurements obtained are confused and diffused using the chaotic sequence generated using the proposed map. The chaos based measurement matrix construction results in reduced data storage and bandwidth requirements. As it needs to store only the parameters required to generate the chaotic sequence. Also, the sensitivity of the chaos to the parameters makes the data transmission secure. The secret key used in the encryption process is dependent on both the input data and the parameter used to generate the chaotic map. Hence the proposed scheme can resist chosen plaintext attack. The key space of the proposed scheme is large enough to thwart statistical attacks. Experimental results and the security analysis verifies the security and effectiveness of the proposed compression-encryption scheme.

Recently, a new kind of image encryption approach using compressive sensing (CS) and double random phase encoding has received much attention due to the advantages such as compressibility and robustness. However, this approach is found to be vulnerable to chosen plaintext attack (CPA) if the CS measurement matrix is re-used. Therefore, designing an efficient measurement matrix updating mechanism that ensures resistance to CPA is of practical significance. In this paper, we provide a novel solution to update the CS measurement matrix by altering the secret sparse basis with the help of counter mode operation. Particularly, the secret sparse basis is implemented by a reality-preserving fractional cosine transform matrix. Compared with the conventional CS-based cryptosystem that totally generates all the random entries of measurement matrix, our scheme owns efficiency superiority while guaranteeing resistance to CPA. Experimental and analysis results show that the proposed scheme has a good security performance and has robustness against noise and occlusion.

A novel image coding scheme under parallel compressive sensing framework is proposed.The scheme achieves resistance to chosen plaintext attack by a counter mode operation.The scheme overcomes the defect of energy information leakage in compressive sensing -based cryptosystem. Recently, using compressive sensing (CS) as a cryptosystem has drawn attention due to its compressibility and low-complexity during the sampling process. However, when applying such cryptosystem to images, how to protect the privacy of the image while keeping efficiency becomes a challenge. In this paper, we propose a novel image coding scheme that achieves combined compression and encryption under a parallel compressive sensing framework, where both the CS sampling and the CS reconstruction are performed in parallel. In this way, the efficiency can be guaranteed. On the other hand, for security, the resistance to chosen plaintext attack (CPA) is realized with the help of the cooperation between a nonlinear chaotic sensing matrix construction process and a counter mode operation. Furthermore, the defect of energy information leakage in CS-based cryptosystem is also overcome by a diffusion procedure. Experimental and analysis results show the scheme achieves effectiveness, efficiency and high security simultaneously.

Akiyama, Goto, Okumura, Takagi, Nuida and Hanaoka introduced an indeterminate equation analogue of learning with errors (IE-LWE) problem as a new computationally hard problem and constructed a candidate of post-quantum cryptosystem, called “Giophantus”. Giophantus satisfies the indistinguishability under chosen plaintext attack (IND-CPA) if IE-LWE problem is computationally infeasible. Akiyama et al., Shimizu and Ikematsu proposed improved Giophantus to the post-quantum standardization project. Beullens, Castryck and Vercauteren proposed an evaluation at one attack against IND-CPA security of Giophantus. However, Akiyama et al. assert that recommended parameters can resist Vercauteren et al.’s attack. Therefore, the security analysis on Giophantus is still needed.

Lattice-based Identity-based encryption (IBE) can both simplify certificate management and resist quantum attack in the real world. Combined Public Key (CPK) technology can be used to enhance the efficiency of IBE schemes. In this paper, we use CPK to construct a more efficient lattice-based IBE scheme based on a variant of learning with errors (LWE) problem, by avoiding complex trapdoor generation algorithm and preimage sampling algorithm required by the existing lattice-based IBE schemes from LWE. Its storage cost is also lower. We show that our IBE scheme is semantically secure against an adaptive chosen plaintext attack (CPA) from all probabilistic polynomial time adversaries in the random oracle model.

In this paper we have analyzed the strength and weakness of scrambled prime key encryption proposed by Haidar et al. [10] for data encryption using key elements which are prime numbers. However, this scheme exhibits its vulnerabilities in the face of chosen plaintext attack. Hence we, in this paper, extended the algorithm by introducing chaos theory and steganography, which offers better security and robustness. We have taken the partially encrypted text from [10] and embedded the same in a carrier image. In this process, we have chosen a novel chaos generator to select the pixels into which the text is to be embedded.

Quantum cryptography has developed some fundamental primitives on encryption of quantum data, such as quantum one-time pad and quantum IND (indistinguishability)-security. Compared with other terms in quantum cryptography, quantum obfuscation attracts less attention and is still in its infancy due to its difficulty in implementation and application. In this paper, we define a quantum point function, construct its obfuscation and then demonstrate the validity of applying quantum point obfuscation to quantum symmetric encryption scheme. We rigorously prove that IND-secure quantum symmetric encryption can be realized by quantum point obfuscators. Furthermore, with the properties of combinability or auxiliary inputs, a quantum point obfuscator can implement IND-CPA (indistinguishability under chosen plaintext attack)-secure quantum symmetric encryption or leakage-resilient quantum symmetric encryption, respectively. This work presents new usage of a quantum obfuscator and will complement the theory of quantum obfuscation.

The evolution of cloud computing and a drastic increase in image size are making the outsourcing of image storage and processing an attractive business model. Although this outsourcing has many advantages, ensuring data confidentiality in the cloud is one of the main concerns. There are state-of-the-art encryption schemes for ensuring confidentiality in the cloud. However, such schemes do not allow cloud datacenters to perform operations over encrypted images. In this paper, we address this concern by proposing 2DCrypt , a modified Paillier cryptosystem-based image scaling and cropping scheme for multi-user settings that allows cloud datacenters to scale and crop an image in the encrypted domain. To anticipate a high storage overhead resulted from the naive per-pixel encryption, we propose a space-efficient tiling scheme that allows tile-level image scaling and cropping operations. Basically, instead of encrypting each pixel individually, we are able to encrypt a tile of pixels. 2DCrypt is such that multiple users can view or process the images without sharing any encryption keys—a requirement desirable for practical deployments in real organizations. Our analysis and results show that 2DCrypt is INDistinguishable under Chosen Plaintext Attack secure and incurs an acceptable overhead. When scaling a $512\times512$ image by a factor of two, 2DCrypt requires an image user to download approximately 5.3 times more data than the un-encrypted scaling and need to work approximately 2.3 s more for obtaining the scaled image in a plaintext.

The paper presented an identity based encryption (IBE) under selective opening attack (SOA) whose security is almost-tightly related to a set of computational assumptions. Our result is a combination of Bellare, Waters, and Yilek’s method [TCC, 2011] for constructing (not tightly) SOA secure IBE and Hofheinz, Koch, and Striecks’ technique [PKC, 2015] on building almost-tightly secure IBE in the multi-ciphertext setting. In particular, we first tuned Bellare et al.’s generic construction for SOA secure IBE to show that a one-bit IBE achieving ciphertext indistinguishability under chosen plaintext attack in the multi-ciphertext setting (with one-sided publicly openability) tightly implies a multi-bit IBE secure under selective opening attack. Next, we almost-tightly reduced such a one-bit IBE to static assumptions in the composite-order bilinear groups employing the technique of Hofheinz et al. This yielded the first SOA secure IBE with almost-tight reduction.

In 2013, Rao and Dutta constructed an efficient attribute based access control mechanism for vehicular ad hoc network (VANET) based on a newly proposed ciphertext-policy attribute-based encryption (CP-ABE) scheme. As the CP-ABE scheme views access policy in normal forms, the length of ciphertext is independent against the number of attributes in the policy besides having constant number of pairing operations for both encryption and decryption functions. In this paper, we cryptanalyze Rao and Dutta's CP-ABE scheme by mounting a chosen plaintext attack to demonstrate that a registered node in VANET can (eavesdrop the conversation to) decrypt a ciphertext with unsatisfied disjunctive normal form policy. Since the security of Rao and Dutta's proposed attribute based access control mechanism for VANET relies on the proposed CP-ABE scheme, our attack indicates that the proposed access control mechanism is insecure. Subsequently, the root cause of the attack and possible solutions are presented to serve as important remarks in designing a secure CP-ABE scheme. We cryptanalyzed Rao and Dutta's CP-ABE scheme by mounting a CPA.A registered node in VANET can decrypt a ciphertext with unsatisfied DNF policy.Root cause of the attack exists in all CP-ABE schemes with normal forms policy.We propose a solution to serve as remarks in designing a secure CP-ABE scheme.

We give an efficient decision procedure that, on input two (acyclic) expressions making arbitrary use of common cryptographic primitives (namely, encryption and pseudorandom generators), determines (in polynomial time) if the two expressions produce computationally indistinguishable distributions for any cryptographic instantiation satisfying the standard security notions of pseudorandomness and indistinguishability under chosen plaintext attack. The procedure works by mapping each expression to a symbolic pattern that captures, in a fully abstract way, the information revealed by the expression to a computationally bounded observer. Our main result shows that if two expressions are mapped to different symbolic patterns, then there are secure pseudorandom generators and encryption schemes for which the two distributions can be distinguished with overwhelming advantage. At the same time if any two (acyclic) expressions are mapped to the same pattern, then the associated distributions are indistinguishable.

The existing Ciphertext-Policy Attribute-Based Encryption (CP-ABE) scheme from lattices can only support a simple threshold access structure, resulting in its limited application scenario. In order to improve the flexibility and expressiveness of the CP-ABE scheme, we present a CP-ABE for circuits from lattices in this paper. The new scheme generates secret key for each attribute of the attribute set by invoking the sampling algorithm from lattices and embeds the attribute set into the secret keys. Meanwhile, to associate the ciphertext with a circuit, we design a Secret Matrix Distribution Mechanism (SMDM) for circuits, which distributes a matrix with specific form to each node of the circuit, and the scheme can generate the ciphertexts by combining the matrices of the leaf nodes. In the decryption phase, the SMDM guarantees the user who satisfies the access structure can decrypt the ciphertexts correctly. Finally, we prove that our scheme is secure against chosen plaintext attack in the selective weak security model under the Learning with Errors (LWE) assumptions.

Due to the threat posed by quantum computers, a series of works investigate the security of cryptographic schemes in the quantum-accessible random oracle model (QROM) where the adversary can query the random oracle in superposition. In this paper, we present tighter security proofs of a generic transformations for key encapsulation mechanism (KEM) in the QROM in the multi-challenge setting, where the reduction loss is independent of the number of challenge ciphertexts. In particular, we introduce the notion of multi-challenge OW-CPA (mOW-CPA) security, which captures the one-wayness of the underlying public key encryption (PKE) under chosen plaintext attack in the multi-challenge setting. We show that the multi-challenge IND-CCA (mIND-CCA) security of KEM can be reduced to the mOW-CPA security of the underlying PKE scheme (with \(\delta \)-correctness) using Open image in new window transformation. Then we prove that the mOW-CPA security can be tightly reduced to the underlying post-quantum assumptions by showing the tight mOW-CPA security of two concrete PKE schemes based on LWE, where one is the Regev’s PKE scheme and the other is a variant of Frodo.

In modern cryptography, block encryption is a fundamental cryptographic primitive. However, it is impossible for block encryption to achieve the same security as one-time pad. Quantum mechanics has changed the modern cryptography, and lots of researches have shown that quantum cryptography can outperform the limitation of traditional cryptography. This article proposes a new constructive mode for private quantum encryption, named $\mathcal{EHE}$, which is a very simple method to construct quantum encryption from classical primitive. Based on $\mathcal{EHE}$ mode, we construct a quantum block encryption (QBE) scheme from pseudorandom functions. If the pseudorandom functions are standard secure, our scheme is indistinguishable encryption under chosen plaintext attack. If the pseudorandom functions are permutation on the key space, our scheme can achieve perfect security. In our scheme, the key can be reused and the randomness cannot, so a $2n$-bit key can be used in an exponential number of encryptions, where the randomness will be refreshed in each time of encryption. Thus $2n$-bit key can perfectly encrypt $O(n2^n)$ qubits, and the perfect secrecy would not be broken if the $2n$-bit key is reused for only exponential times. Comparing with quantum one-time pad (QOTP), our scheme can be the same secure as QOTP, and the secret key can be reused (no matter whether the eavesdropping exists or not). Thus, the limitation of perfectly secure encryption (Shannon's theory) is broken in the quantum setting. Moreover, our scheme can be viewed as a positive answer to the open problem in quantum cryptography "how to unconditionally reuse or recycle the whole key of private-key quantum encryption". In order to physically implement the QBE scheme, we only need to implement two kinds of single-qubit gates (Pauli $X$ gate and Hadamard gate), so it is within reach of current quantum technology., 13 pages, 1 figure. Prior version appears in eprint.iacr.org(iacr/2017/1247). This version adds some analysis about multiple-message encryption, and modifies lots of contents. There are no changes about the fundamental results

Ciphertext policy attribute-based encryption (CP-ABE) is a promising cryptographic technology that provides fine-grained access control as well as data confidentiality. It enables one sender to encrypt the data for more receivers, and to specify a policy on who can decrypt the ciphertext using his/her attributes alone. However, most existing ABE schemes are constructed on bilinear maps and they cannot resist quantum attacks. In this paper, we propose a multi-authority CP-ABE (MA-CPABE) scheme on ideal lattices which is still secure in post-quantum era. On one hand, multiple attribute authorities are required when user's attributes cannot be managed by a central authority. On the other hand, compared with generic lattice, the ideal lattice has extra algebraic structure and can be used to construct more efficient cryptographic applications. By adding some virtual attributes for each authority, our scheme can support flexible threshold access policy. Security analysis shows that the proposed scheme is secure against chosen plaintext attack (CPA) in the standard model under the ring learning with errors (R-LWE) assumption.

Matrix multiplication is a very basic computation task in many scientific algorithms. Recently Lei et al. proposed an interesting outsource protocol for matrix multiplication in cloud computing. Their proposal is very efficient, however we find that the proposal is not so secure from the view of cryptography. Concretely, the cloud can easily distinguish which matrix has been outsourced from two candidate matrixes. That is, their proposal does not satisfy the indistinguishable property under chosen plaintext attack. Finally we give an improved outsource protocol for matrix multiplication in cloud computing.

Since the first appearance in Fridrich’s design, the usage of permutation–diffusion structure for designing digital image cryptosystem has been receiving increasing research attention in the field of chaos-based cryptography. Recently, a novel chaotic image cipher using a single-round modified permutation–diffusion pattern (ICMPD) was proposed. Unlike traditional permutation–diffusion structure, the permutation of ICMPD is operated on bit level instead of pixel level and its diffusion stage is operated on masked pixels, which are obtained by carrying out the classical affine cipher, instead of plain pixels. Following a divide-and-conquer strategy, this paper reports that ICMPD can be compromised by a chosen-plaintext attack efficiently and the involved data complexity is linear to the size of the plain-image. Moreover, the relationship between the cryptographic kernel at the diffusion stage of ICMPD and the classical modulo addition then XORing operation is explored thoroughly.

After analyzing Yang's verifiable quantum secret sharing (VQSS) scheme, we show that in their scheme a participant can prepare a false quantum particle sequence corresponding to a forged share, while other any participant cannot trace it. In addition, an attacker or a participant can forge a new quantum sequence by transforming an intercepted quantum sequence; moreover, the forged sequence can pass the verification of other participants. So we propose a new VQSS scheme to improve the existed one. In the improved scheme, we construct an identity-based quantum signature encryption algorithm, which ensures chosen plaintext attack security of the shares and their signatures transmitted in the quantum tunnel. We employ dual quantum signature and one-way function to trace against forgery and repudiation of the deceivers (dealer or participants). Furthermore, we add the reconstruction process of quantum secret and prove the security property against superposition attack in this process.

In this paper, we describe a cryptanalysis of image encryption scheme recently proposed by Chun-Yan Song, Yu-Long Qiao, and Xing-Zhou Zhang. The scheme is based on a spatiotemporal chaos with a dynamic keystream generator, and its security is claimed to rely in utilized the plainimage in the keystream generation process to obtain a different keystream for every plainimage/cipherimage pair. However, two flaws are investigated and prove that the security of the proposal against chosen plaintext attack is groundless. Simulations conducted demonstrate that the plainimage can be recovered under partial attack with an acceptable perceptual quality. Moreover, a total break is possible, but a large number of plain-image/cipher-image pairs is needed. HighlightsA cryptanalysis of an image encryption scheme based on spatiotemporal chaos is presented.We gave a complete and partial break of the cryptosystem under study.We prove that the studied cryptosystem is not sufficiently secure against chosen plaintext attack.Results suggest that a partial attach needs smaller number of plain/ciphered images with acceptable perceptual qualities.

A multiple-image cryptosystem is proposed based on the cascaded fractional Fourier transform. During an encryption procedure, each of the original images is directly separated into two phase masks. A portion of the masks is subsequently modulated into an interim mask, which is encrypted into the ciphertext image; the others are used as the encryption keys. Using phase truncation in the fractional Fourier domain, one can use an asymmetric cryptosystem to produce a real-valued noise-like ciphertext, while a legal user can reconstruct all of the original images using a different group of phase masks. The encryption key is an indivisible part of the corresponding original image and is still useful during decryption. The proposed system has high resistance to various potential attacks, including the chosen-plaintext attack. Numerical simulations also demonstrate the security and feasibility of the proposed scheme.

Signcryption as a cryptographic primitive can carry out signature and encryption simultaneously at a remarkably reduced cost. Identity-based cryptography is more convenient than public key infrastructure-based cryptography in certificate management. As a result, identity-based signcryption has been studied extensively, and many efficient and provably secure constructions have been proposed. However, most of these schemes are based on intractability assumptions from number theory, and these assumptions have been threatened by the booming quantum computation. Therefore, a recent trend in cryptography is to construct cryptosystems that are based on lattice-based intractability assumptions because of their plausible features of quantum attack resistance. In this paper, several identity-based signcryption schemes from lattice hardness assumptions are proposed. In the standard model, these schemes are indistinguishable against inner adaptively chosen ciphertext attacks IND-CCA2 and strongly unforgeable against inner chosen message attacks. In our construction, it does not matter whether the original encryption scheme used to construct signcryption is deterministic or probabilistic; the resulted signcryption schemes can reach IND-CCA2 security. To achieve this, we carefully combine three techniques-the identity-based encryption from lattice due to Agrawal-Boneh-Boyen EUROCRYPT 2010, the framework of lattice-based short signature due to Boyen Public Key Cryptography 2010, and the Canetti-Halevi-Katz abbr. CHK technique, with necessary and tailored optimization-for transforming an i¾? + 1-level indistinguishable under chosen plaintext attack secure hierarchical identity-based encryption HIBE into an i¾? level IND-CCA2 secure HIBE scheme. In addition, our security proof also contains a more efficient simulation tool that might have separate interest in cryptographic applications. Copyright © 2015 John Wiley & Sons, Ltd.

Proxy re-encryption PRE is a cryptographic primitive that allows a proxy to turn an Alice's ciphertext into a Bob's ciphertext on the same plaintext. At present, there are many different PRE schemes that have been proposed with different properties. However, all of them are based on the logarithm assumption and the large integer factorization assumption except for a bidirectional PRE scheme over lattices. In this paper, we construct the first multi-use unidirectional PRE scheme based on lattices. In addition, the generation of the PRE key does not interact with two users, and the scheme can resist collusion attacks. Moreover, it is proved chosen plaintext attack secure in the standard model based on the Learning With Errors assumption. Finally, an identity-based PRE is obtained from the basic construction. Copyright © 2015 John Wiley & Sons, Ltd.

An efficient identity-based encryption IBE scheme over lattice is proposed in this paper. Under the hardness of the learning with errors LWE problem, the proposed scheme is semantic secure against adaptive chosen identity and chosen plaintext attack in the standard model. To improve the efficiency of the lattice-based IBE scheme, unlike the identity string is encoded into a matrix by a group of public matrices in several known constructions, the identity string of l bits is encoded into a vector with the help of vectors in this paper. With the help of this idea, we achieve the private key extraction of IBE scheme at the same lattice. Then, the public key of the proposed scheme only consists of one matrix and vectors, compared with that the public keys of the known lattice-based IBE schemes all consist as a group of matrices. Hence, the public key size of this scheme is shorter than that of the known constructions.

In recent years, chaos-based image encryption algorithms have attracted much attention. Particularly, with larger data capacity and higher correlation among pixels, encryption of colour images demands better statistic and diffusion properties of image algorithms than that of grey images. In this paper, a chaos-based algorithm aiming at colour image encryption is proposed. Two 3D chaotic systems are used as key generators for three colours of colour images’ pixels. 4-Pixel Feistel structure and functions based on multiple chaotic maps are used to improve the statistic and diffusion properties of cipher image. Dependent encryption progress is used to resist certain cryptanalysis methods, such as known-/chosen plaintext attack and chosen cipher attack. According to large number of simulation experiments, with good speed performance being taken into account, our algorithm has better properties and higher security level than certain other chaos-based colour image encryption algorithms.

This paper proposes a new block image encryption scheme based on hybrid chaotic maps and dynamic random growth technique. Since cat map is periodic and can be easily cracked by chosen plaintext attack, we use cat map in another securer way, which can completely eliminate the cyclical phenomenon and resist chosen plaintext attack. In the diffusion process, an intermediate parameter is calculated according to the image block. The intermediate parameter is used as the initial parameter of chaotic map to generate random data stream. In this way, the generated key streams are dependent on the plaintext image, which can resist the chosen plaintext attack. The experiment results prove that the proposed encryption algorithm is secure enough to be used in image transmission systems.

Attribute-based encryption (ABE) has been an active research area in cryptography due to its attractive applications. But almost all ABE scheme are based on bilinear maps, which leave them vulnerable to quantum cryptanalysis. The cryptographic system based on lattices is considered to be able to resist the quantum attack, and the computational efficiency is high. Therefore, the encryption scheme based on lattice theory has received wide attention in recent years. At present, the research of the attribute based encryption scheme on ideal lattices is lacking, and there are many problems need to be solved. Lots of existing schemes support only a single access policy and cannot support flexible expressions. For solving the problem of designing access structure in attribute-based encryption scheme under quantum environment, combined with Zhu’s scheme, an attribute-based encryption scheme supporting tree access structures on ideal lattices is introduced. The scheme adopts tree-access structure to express access strategy, the leaf nodes of the tree represent attributes, and the non-leaf nodes represent logical operators. The access tree can express the access policy flexibly by Shamir threshold secret sharing technology, including “and”, “or”, “threshold” operation. The scheme is proved to be secure against chosen plaintext attack under the standard mode. The analysis shows that our scheme can resist the quantum attack and realize the flexible access strategy with the better performance.

Order-preserving encryption (OPE) has been proposed as a privacy-preserving query method for cloud computing. Existing researches of OPE diverge into two groups. One group focuses on single data provider scenarios and achieves strong security notion such as indistinguishability under ordered chosen plaintext attack (IND-OCPA). Another group of research designs multi-provider schemes and provides weaker security guarantees than those of single provider schemes. In this paper, we propose a novel security notion for multi-provider scenario, indistinguishability under multi-provider ordered chosen plaintext attack (IND-MPOPCA), which guarantees equivalent security level as IND-OCPA while hiding the frequency of plaintexts and enabling multi-provider data submissions and queries. We develop a multi-provider randomized order technique to construct our MPOPE scheme to achieve the IND-MPOPCA security notion. We also conduct extensive experiments to prove the practicality and efficiency of our proposed scheme.

In 2006, Yu et al. presented a new cryptographic scheme based on delayed chaotic neural networks. However, Yang et al. found a fundamental flaw in Yu-Cao scheme by means of chosen plaintext attack in 2009. In this paper, a more effective method is described through the analysis of the Exclusive-or operation. As a result, it makes this cryptographic scheme insecure.

Attribute-Based Encryption (ABE) schemes show unprecedented flexibility and expressiveness through the introduction of access policies. Compared to ABE schemes for thresholds or circuits from lattices, Linear Secret Sharing Schemes (LSSS) matrix-based ABE is more difficult to design for its abstract mathematical structure. We propose an ABE scheme for LSSS matrix from lattices in this work. The prior lattice-based ABE scheme for LSSS matrix constructed a large virtual encryption matrix to embed the LSSS matrix in secret key. We use a completely different but common method in lattice-based encryption schemes to achieve the same task. Moreover, we prove that our scheme is secure against chosen plaintext attack in the selective security model under the Learning with Errors (LWE) assumptions.

Proxy re-encryption (PRE) is an important cryptographic primitive used for private information sharing. However, the recent advance in quantum computer has potentially crippled its security, as the traditional decisional Diffie-Hellman (DDH)-based PRE is venerable to the quantum attack. Thus, learning with errors (LWE)-based PRE schemes, as a kind of latticebased construction with the inherent quantum-resistant property, has attracted special research interest. Unfortunately, the main drawback of lattice-based public key encryption scheme is noise management after multiplication evaluation. Many cryptographers have been devoted to controlling the expansion of noise. In this line of work, Dagdelen-Gajek-G¨opfert (DGG) put forth the notion of learning with errors in the exponent (LWEE) which is based on lattice and group-theoretic assumption, meanwhile demonstrated a paradigm for constructing efficient quantum resistance public key schemes. In this paper, on top of DGG, we construct a single-bit, single-hop and unidirectional LWEE- based PRE scheme with indistinguishable chosen plaintext attack (IND-CPA) security. To the best of our knowledge, our scheme is the first LWEE-based PRE scheme.

The attribute based signature scheme could verify the signature by the attribute instead of public key. But, a large number of bilinear operations are concentrated in the verification process, so the amount of computation required for signature verification is much larger than that of signature generation. To solve this problem, this paper proposed an attribute based signature scheme with aided-verification, which outsources the bilinear mapping. It supports LSSS matrix, with flexible expression ability. It proved the unforgeability and outsourcing computational completeness under chosen plaintext attack with the Diffie-Hellman problem assumption. The proposal could be used in mobile devices with limited computing power.

A double-image encryption is proposed based on the discrete fractional random transform and logistic maps. Firstly, an enlarged image is composited from two original plaintexts, in which the pixel positions are relocated and the intensity values are changed by a chaotic confusion–diffusion process, and then two scrambled plaintexts are recovered from the enlarged image. Secondly, the two scrambled plaintexts are encoded into the phase and amplitude part of a complex function which is encrypted into a ciphertext with stationary white noise distribution by using the discrete fractional random transform generated based on logistic map. Not only the initial values of the logistic maps used in the cryptosystem but also the phase distribution produced in the encryption process can be used as private keys, which makes the proposed scheme has the characteristic of asymmetric encryption technique and high resistance against to the conventional attacks such as chosen plaintext attack, ciphertext-only attack. Simulation results and security analysis verify the feasibility and effectiveness of the proposed method.