Search

In this paper, we consider the problem of constructing new plaintext aware encryption in the standard model. A new hybrid asymmetric encryption scheme is presented using a new key encapsulation method and a data encapsulation method. To prove the presented asymmetric encryption scheme is simulatable, we put forward some new sufficient conditions for judging a group to be simulatable. By introducing a new assumption called linear Diffie-Hellman knowledge assumption, we prove the proposed hybrid asymmetric encryption scheme is PA2.

Plaintext-aware encryption is a simple concept: a public-key encryption scheme is plaintext aware if no polynomial-time algorithm can create a ciphertext without "knowing" the underlying message. However, the formal definitions of plaintext awareness are complex. This paper analyses these formal security definitions and presents the only known viable strategy for proving a scheme is PA2 plaintext aware. At the heart of this strategy is a new notion called PA1+ plaintext awareness. This security notion conceptually sits between PA1 and PA2 plaintext awareness (although it is formally distinct from either of these notions). We show exactly how this new security notion relates to the existing notions and how it can be used to prove PA2 plaintext awareness.

An increasing demand of secure data transmission over internet leads to the challenge of implementing a consistent cryptosystem. In 2004, USA navy published the patent which highlights the importance of fractal as an encryption/decryption key in a cryptosystem [1]. Fractal possess butterfly effect i.e. sensitivity to initial condition, due to which small change in input produces a major change in output. This paper summarizes the various recent image encryption techniques in which fractal key is used to encrypt/decrypt followed by substitution, scrambling and diffusion techniques to provide strong cryptosystem. The algorithms covered both private key encryption as well as public key encryption technique in the paper. The analysed algorithms include a set of fractal function such as Mandelbrot set, Julia set, Hilbert curve, 3D fractal, multi-fractal, IFS and chaotic function to generate a complex key used in the encryption process. Corresponding performance of each algorithm is analysed by PSNR test, key space, sensitivity analysis and correlation coefficient value between the adjacent pixels of both images (Original image and encrypted image) which shows significant improvement in performance over the traditional encryption methods.

Recently, based on the Paillier cryptosystem [1] , Yi et al. outline a distributed ElGamal cryptosystem which allows for both a much simpler distributed key generation procedure and a more efficient distributed decryption of messages from a large plaintext domain [2] . In this paper, we analyze the security of their proposed variant of ElGamal encryption scheme and demonstrate that their proposed variant is not secure as claimed. Thus, whether an additively homomorphic cryptosytem satisfying the desired properties exists remains an open question.

Although many encryption methods are available, there is always an ongoing need for more to resist the adversaries’ ever-growing analytical skills and techniques. We propose in this paper an innovative method for text encryption. We devise a random number generation function that creates sequences of signed random numbers that depend on both plaintext and key. The random numbers support the functionality of four random operations: random mutation, random cyclic shifting, random permutation, and dirty symbol random insertion. These operations ensure the data security by steadily melting the statistical structure of plaintext and relationships to a key. The experiments with our prototype implementation showed that our method has high effectiveness (in terms of diffusion, confusion, avalanche) and high efficiency with respect to the computation demands. Keywords: Text encryption, Lookback text encryption, Random encryption operations, Security random generator

This paper proposes a novel reversible data hiding scheme for encrypted images by using homomorphic and probabilistic properties of Paillier cryptosystem. In the proposed method, groups of adjacent pixels are randomly selected, and reversibly embedded into the rest of the image to make room for data embedding. In each group, there are a reference pixel and a few host pixels. Least significant bits (LSBs) of the reference pixels are reset before encryption and the encrypted host pixels are replaced with the encrypted reference pixel in the same group to form mirroring ciphertext groups (MCGs). In such a way, the modification on MCGs for data embedding will not cause any pixel oversaturation in plaintext domain and the embedded data can be directly extracted from the encrypted domain. In an MCG, the reference ciphertext pixel is kept unchanged as a reference while data hider embeds the encrypted additional data into the LSBs of the host ciphertext pixels by employing homomorphic multiplication. On the receiver side, the hidden ciphertext data can be retrieved by employing a modular multiplicative inverse operation between the marked host ciphertext pixels and their corresponding reference ciphertext pixels, respectively. After that, the hidden data are extracted promptly by looking for a one-to-one mapping table from ciphertext to plaintext. Data extraction and image restoration can be accomplished without any error after decryption. Compared with the existing works, the proposed scheme has lower computation complexity, higher security performance, and better embedding performance. The experiments on the standard image files also certify the effectiveness of the proposed scheme.

Bellare, Boldyreva, and O’Neill (CRYPTO ’07) initiated the study of deterministic public-key encryption as an alternative in scenarios where randomized encryption has inherent drawbacks. The resulting line of research has so far guaranteed security only for adversarially-chosen plaintext distributions that are independent of the public key used by the scheme. In most scenarios, however, it is typically not realistic to assume that adversaries do not take the public key into account when attacking a scheme.

Database encryption is essential for cloud database systems. For a large database, decryption could take a lot of computational time. Therefore, verifying an encryption that contains a correct plaintext without decryption becomes significant for a large database system. Plaintext-checkable encryption (PCE) is a potential tool for such database systems, which is first proposed by Canard et al. in CT-RSA 2012. Although the generic PCE in the random oracle model has been studied intensively, the generic PCE in the standard model and its efficient implementation are still challenging problems. This paper presents the first generic PCE in the standard model using smooth projective hash function (SPHF) and prove its s-priv1-cca security, which is independent of current unlink security. Based on the instantiated SPHF from DDH assumption, we obtain the most efficient PCE in the standard model, without any pairing operation. Finally, we improve two existing generic constructions in the random oracle model so that they are secure under chosen ciphertext attack.

In this paper, a new two-dimensional Logistic ICMIC cascade map (2D-LICM) is proposed based on cascade modulation couple (CMC) model. Performance evaluations show that it has hyperchaotic behavior, wide chaotic range and large complexity. Based on this map, a novel image encryption algorithm is designed by employing bit-level permutation and diffusion simultaneously. The bit-level permutation is performed by circular shifting, and the bit-level diffusion is carried out by exclusive or ( xor ) and reverse operations. In addition, the initial values of chaotic system are updated in real time according to the obtained ciphertext and it greatly improves the ability of resisting known plaintext attack and chosen plaintext attack. Simulation results and performance analysis show that this algorithm has good encryption effect and high efficiency. It can resist typical attacks including statistical, brute-force, differential attacks and so forth.

This paper presents a solution for secure and efficient image encryption with the help of self-adaptive permutation–diffusion and DNA random encoding. The plain image is firstly converted to DNA sequence using random encoding rules, so as to disarrange the bit distribution of the plaintext. A self-adaptive permutation–diffusion procedure is subsequently introduced for further encryption. The quantization processes of the permutation and diffusion procedures are disturbed by the intrinsic features of the plaintext, with the introduced disturbances can be automatically retrieved in the decryption end. The security of the system originates from the plaintext-related quantization of the encryption process which makes the cryptosystem secure against plaintext attack. Besides, the reusability of the random variables can dramatically promote the efficiency of the cryptosystem, which renders great potential for real-time secure image applications.

Image encryption techniques aims to protect the content of image with higher efficiency and security than conventional cryptographic methods by making use of special properties of image. This paper presents an image encryption model based on two-dimensional partitioned cellular automaton. The model has the same topology as a digital image and is flexible to images with different color depth; it is efficient as only substitution and permutation operations are involved; the properties of cellular automata make the model easy for Very Large Scale Integration (VLSI) implementation. Moreover, unlike most known image encryption algorithms, this model can support parallel computing. A probability cellular automaton called coloring model, is proposed to study the sensitivity of the encryption model. It shows that the model meets the global strict avalanche criterion in at most M + N + 7 rounds of encryption for an M × N image. Several approaches are proposed to estimate the minimal number of rounds to fulfill the global strict avalanche criterion; simulation shows that the maximal error is only one round. An image encryption algorithm based on this model is presented, which is demonstrated by experiments to own the properties of randomness and sensitivity.

To lower communication complexity, a Certificateless homomorphic encryption (CLHE) scheme based on the Learning with errors (LWE) problem is constructed by introducing a new technique called probabilistic encoding with weakly homomorphic property. This technique can conveniently convert an intended message into two elements in a ring, which will be respectively encrypted under both public keys of a user in certificateless cryptosystem. Upon knowing both elements simultaneously, the original message can be easily recovered. It is hidden perfectly by the probabilistic property of encoding. This CLHE removes evaluation keys by using the approximate eigenvector method given by Gentry et al., which makes it into a pure CLHE. It is proven to be semantic secure in the Random oracle model (ROM). The results indicate it is able to homomorphically evaluate any functions in a class functions with given multiplicative depth L.

Over the past two decades, chaos-based encryption appeared as an original application for nonlinear dynamics and deterministic chaos to encrypt and decrypt data. In this paper, an implementation of digital image encryption scheme based on the Lorenz chaotic system is proposed. While in the process of generating chaotic key stream, the hash value of the plain image is embedded in the proposed cryptosystem to dynamically alter the initial secret keys to increase the security level. The proposed digital image encryption algorithm is described in detail along with its security analysis and implementation. The experimental results show that the proposed digital image encryption algorithm is efficient and has high security features and is suitable for practical uses across insecure networks.

Recently, a feedback image encryption algorithm with compound chaotic stream cipher based on perturbation was proposed. This paper analyzes security of the algorithm and reports that there exist some security defects, i.e., encryption of a pixel is independent on the position scrambling and the encryption round is controlled by the users. Based on them, a chosen-ciphertext attack is proposed to obtain the equivalent version of the secret key of the algorithm with $$n\cdot \lceil \log _{256} MN +2 \rceil $$ chosen cipher-images, where $$M\times N$$ is the size of the corresponding plain-images and n is the round number of encryption.

Efficient searching on encrypted data outsourced to the cloud remains a research challenge. Identity-based encryption with equality test (IBEET) scheme has recently been identified as a viable solution, in which users can delegate a trapdoor to the server and the server then searches on user outsourced encrypted data to determine whether two different ciphertexts are encryptions of the same plaintext. Such schemes are, unfortunately, inefficient particularly for deployment on mobile devices (with limited power/battery life and computing capacity). In this paper, we propose an efficient IBEET scheme with bilinear pairing, which reduces the need for time-consuming HashToPoint function. We then prove the security of our scheme for one-way secure against chosen identity and chosen ciphertext attacks (OWIDCCA) in the random oracle model (ROM). The performance evaluation of our scheme demonstrates that in comparison to the scheme of Ma (2016), our scheme achieves a reduction of 36.7% and 39.24% in computation cost during the encryption phase and test phase, respectively, and that our scheme is suitable for (mobile) cloud deployment. We propose an identity-based encryption with equality test (IBEET) scheme using bilinear pairing for cloud storage.We show that our proposed concrete scheme is provably secure. It satisfies required security properties.Detailed performance analysis and experimental result are given.

Objectives: The principal objective of this paper is to develop an enhanced algorithm of cryptography through the hybridization of existing symmetric and asymmetric encryption. Methods/Analysis: The strength of several prevailing symmetric and asymmetric encryption were utilized in the proposed methodology. ElGamal’s key security based on difficulty of solving discrete logarithm, Chaos-based’s avalanche effect of using multiple keys, RSA’s security based on the difficulty of factorization of large numbers and AES’s S-Box mapping, which makes the encryption complex and unpredictable were adapted. Findings: The strength of security of the proposed hybrid algorithm is tested by the provided examples. It was found out that with the use of different keys in encryption, various ciphertexts were generated. The published public keys using such algorithm also make it infeasible to intrude because of the difficulty of solving discrete logarithm with large prime numbers. Furthermore, the value of the ciphertext of the proposed method is significantly different and, in some cases, larger than that of RSA’s. Applications: With this newly enhanced hybrid algorithm of data encryption, transferring and conveying of data will be much more secured.

Motivated by applications in large storage systems, we initiate the study of incremental deterministic public-key encryption. Deterministic public-key encryption, introduced by Bellare, Boldyreva, and O'Neill (CRYPTO '07), provides an alternative to randomized public-key encryption in various scenarios where the latter exhibits inherent drawbacks. A deterministic encryption algorithm, however, cannot satisfy any meaningful notion of security for low-entropy plaintexts distributions, but Bellare et al. demonstrated that a strong notion of security can in fact be realized for relatively high-entropy plaintext distributions. In order to achieve a meaningful level of security, a deterministic encryption algorithm should be typically used for encrypting rather long plaintexts for ensuring a sufficient amount of entropy. This requirement may be at odds with efficiency constraints, such as communication complexity and computation complexity in the presence of small updates. Thus, a highly desirable property of deterministic encryption algorithms is incrementality: Small changes in the plaintext translate into small changes in the corresponding ciphertext. We present a framework for modeling the incrementality of deterministic public-key encryption. Our framework extends the study of the incrementality of cryptography primitives initiated by Bellare, Goldreich and Goldwasser (CRYPTO '94). Within our framework, we propose two schemes, which we prove to enjoy an optimal tradeoff between their security and incrementality up to lower-order factors. Our first scheme is a generic method which can be based on any deterministic public-key encryption scheme, and, in particular, can be instantiated with any semantically secure (randomized) public-key encryption scheme in the random-oracle model. Our second scheme is based on the Decisional Diffie---Hellman assumption in the standard model. The approach underpinning our schemes is inspired by the fundamental "sample-then-extract" technique due to Nisan and Zuckerman (JCSS '96) and refined by Vadhan (J. Cryptology '04), and by the closely related notion of "locally computable extractors" due to Vadhan. Most notably, whereas Vadhan used such extractors to construct private-key encryption schemes in the bounded-storage model, we show that techniques along these lines can also be used to construct incremental public-key encryption schemes.

A symmetric key image cryptosystem based on the piecewise linear map is presented in this paper. In this cryptosystem, the encryption process and the decryption process are exactly same. They both include the same operations of plaintext-related scrambling once, diffusion twice and matrix rotating of 180 degrees four times. The length of secret key in the system is 64d where d is a positive integer. The proposed system can fight against the chosen/known plaintext attacks due to the using of plaintext-related scrambling. The simulate results and comparison analysis show that the proposed system has many merits such as high encryption/decryption speed, large key space, strong key sensitivity, strong plaintext sensitivity, strong cipher-text sensitivity, good statistical properties of cipher images, and large cipher-text information entropy. So the proposed system can be applied to actual communications.

We present a non-embedding image cryptosystem to accomplish the meaningful encryption. Thanks to the non-embedding superiority, the encrypted images are robust to both human eyes and steganalysis methods.We incorporate coupled dictionary learning and compressive sensing techniques into an unified framework, and further apply it to accomplish the task of non-embedding image encryption.Our scheme can reconstruct an image of more information with the image of little information. In this paper, we propose a novel image cryptosystem, which enables to encrypt the secret images with a smaller-size cover image. Compared with the existing meaningful encryption methods, our cryptosystem has three advantages: (1) non-embedding encryption, i.e., there isnt any data embedding into the cover image during the encryption process. (2) Our cryptosystem can simultaneously encrypt multiple secret images with one cover image, which greatly improves the security of secret images. (3) Our cryptosystem can accomplish not only the meaningful encryption, but also the meaningless encryption. Thus, people dont switch encryption methods when meeting different encryption requirements. Our scheme leverages the popular coupled dictionary learning and compressive sensing techniques to accomplish the whole task. Specifically, we use the coupled dictionaries to build connection between the cover image and the secret image, and apply the compressive sensing to decrypt the secret image. To demonstrate the effectiveness of the proposed cryptosystem, a series of experiments are conducted. Experimental results on gray images and colorful RGB images verify its superiority.

A joint image compression and encryption scheme based on JPEG is proposed.Encryption is mainly realized at JPEGs transformation stage.The scheme is format compliant to JPEG with tunable encryption parameters.Good encryption and compression performances can be achieved simultaneously. In this paper, we propose a novel joint image compression and encryption scheme based on JPEG standard. We realize image encryption at JPEGs transformation stage. Instead of only using 88 discrete cosine transform (DCT) for transformation, we generate new orthogonal transforms by embedding an extra rotation angle of to different stages butterflies in 88 DCTs flow-graph, and then apply them alternatively for transformation according to a predefined secret key. By carefully controlling the number of rotation angles embedded, the quality control of encrypted images can also be achieved. The encryption algorithm is further enhanced by performing block permutation before the entropy encoding stage. Extensive experiments have been conducted to show the good protection and compression performance of our encryption schemes. Finally, a detailed security analysis is provided to show the encryption schemes resistance to various cryptanalysis methods, such as brute-force attack, key sensitivity analysis, replacement attack and statistical attack.

We propose a novel color image encryption scheme based on DNA permutations. In the proposed scheme, the chaotic pseudo-random sequences for encryption depend on the plaintext image and secret keys. Besides, the proposed DNA permutation and addition/subtraction operations can break the bit planes of the plaintext image entirely. Therefore, the proposed scheme is sensitive to the plaintext image and can resist common attacks such as differential attack, brute-force attack, and statistical attack. Simulation results show the feasibility and effectiveness of the proposed scheme.

We give a new black-box transformation from any semantically secure encryption scheme into a non-malleable one which has a better rate than the best previous work of Coretti et al. (in: Kushilevitz and Malkin (eds) TCC 2016-A, Part I, Springer, Heidelberg, 2016). We achieve a better rate by departing from the "matrix encoding" methodology used by previous constructions, and working directly with a single codeword. We also use a Shamir secret-share packing technique to improve the rate of the underlying error-correcting code.

We show how to transform any semantically secure encryption scheme into a non-malleable one, with a black-box construction that achieves a quasi-linear blow-up in the size of the ciphertext. This improves upon the previous non-black-box construction of Pass, Shelat and Vaikuntanathan (Crypto '06). Our construction also extends readily to guarantee non-malleability under a bounded-CCA2 attack, thereby simultaneously improving on both results in the work of Cramer et al. (Asiacrypt '07). Our construction departs from the oft-used paradigm of re-encrypting the same message with different keys and then proving consistency of encryption. Instead, we encrypt an encoding of the message; the encoding is based on an error-correcting code with certain properties of reconstruction and secrecy from partial views, satisfied, e.g., by a Reed---Solomon code.

Ye and Zhou [Appl. Soft. Comput. 22 (2014) 351–357] proposed an efficient chaotic based image encryption scheme which only employs diffusion, while usually both confusion and diffusion are used for encryption structures. We present both chosen-plaintext and chosen-ciphertext attacks against the scheme for any number of its rounds r by exploiting r -round differentials with probability 1. The result shows that the encryption structure proposed by Ye and Zhou does not fulfill basic requirements of a secure image encryption scheme.

Recently, a number of chaos-based image encryption algorithms that use low-dimensional chaotic map and permutation-diffusion architecture have been proposed. However, low-dimensional chaotic map is less safe than high-dimensional chaotic system. And permutation process is independent of plaintext and diffusion process. Therefore, they cannot resist efficiently the chosen-plaintext attack and chosen-ciphertext attack. In this paper, we propose a hyper-chaos-based image encryption algorithm. The algorithm adopts a 5-D multi-wing hyper-chaotic system, and the key stream generated by hyper-chaotic system is related to the original image. Then, pixel-level permutation and bit-level permutation are employed to strengthen security of the cryptosystem. Finally, a diffusion operation is employed to change pixels. Theoretical analysis and numerical simulations demonstrate that the proposed algorithm is secure and reliable for image encryption.

Revocation and key evolving paradigms are central issues in cryptography, and in PKI in particular. A novel concern related to these areas was raised in the recent work of Sahai, Seyalioglu, and Waters (CRYPTO 2012) who noticed that revoking past keys should at times (e.g., the scenario of cloud storage) be accompanied by revocation of past ciphertexts (to prevent unread ciphertexts from being read by revoked users). They introduced revocable-storage attribute-based encryption (RS-ABE) as a good access control mechanism for cloud storage. RS-ABE protects against the revoked users not only the future data by supporting key-revocation but also the past data by supporting ciphertext-update, through which a ciphertext at time T can be updated to a new ciphertext at time T + 1 using only the public key. Motivated by this pioneering work, we ask whether it is possible to have a modular approach, which includes a primitive for time managed ciphertext update as a primitive. We call encryption which supports this primitive a "self-updatable encryption" (SUE). We then suggest a modular cryptosystems design methodology based on three sub-components: a primary encryption scheme, a key-revocation mechanism, and a time-evolution mechanism which controls the ciphertext self-updating via an SUE method, coordinated with the revocation (when needed). Our goal in this is to allow the self-updating ciphertext component to take part in the design of new and improved cryptosystems and protocols in a flexible fashion. Specifically, we achieve the following results:We first introduce a new cryptographic primitive called self-updatable encryption (SUE), realizing a time-evolution mechanism. In SUE, a ciphertext and a private key are associated with time. A user can decrypt a ciphertext if its time is earlier than that of his private key. Additionally, anyone (e.g., a cloud server) can update the ciphertext to a ciphertext with a newer time. We also construct an SUE scheme and prove its full security under static assumptions. Following our modular approach, we present a new RS-ABE scheme with shorter ciphertexts than that of Sahai et al. and prove its security. The length efficiency is mainly due to our SUE scheme and the underlying modularity. We apply our approach to predicate encryption (PE) supporting attribute-hiding property, and obtain a revocable-storage PE (RS-PE) scheme that is selectively-secure. We further demonstrate that SUE is of independent interest, by showing it can be used for timed-release encryption (and its applications), and for augmenting key-insulated encryption with forward-secure storage. A new cryptographic primitive called self-updatable encryption is introduced to realize a time-evolution mechanism.A revocable-storage attribute-based encryption scheme with shorter ciphertexts was proposed by following our modular approach.A revocable-storage predicate encryption scheme that additionally supports attribute-hiding property is presented.

We propose two Key-Policy Attribute-Based Encryption (KP-ABE) schemes for Linear Secret-Sharing Scheme (LSSS)-realizable Monotone Access Structure (MAS). We show that the first construction is secure against Chosen Plaintext Attacks (CPAs) while the second scheme is secure against Chosen Ciphertext Attacks (CCAs), without introducing any random oracle heuristic. Both the schemes enjoy constant-size ciphertext, constant number of pairing operations, and constant computation cost during encryption and decryption. We further propose two non-monotone access structure variants, one is CPA secure and another is CCA secure, preserving the same functionality as that of MAS primitives. We thereafter present a large attribute universe KP-ABE for MAS, still utilizing low computation cost together with constant number of pairing operations and public parameters. Unlike the existing approaches, this does not impose a bound on the size of attribute sets used in encryption, however, the security is in random oracle model. Our final result is a dual-policy ABE supporting LSSS-realizable MAS with significantly low communication and computation cost. Furthermore, we extend our KP-ABE to efficient key-policy attribute-based broadcast encryption. While the secret key in all our constructions has quadratic-size in the number of attributes, the number of pairing evaluations is constant. The CPA and CCA security against selective-adversary of proposed schemes are achieved under the decisional Bilinear DiffieHellman Exponent assumption over prime order groups.

The principle of compressed sensing (CS) can be applied to a cryptosystem in which the sensing matrix is employed for the secret key. In this letter, we study the security of a CS-based cryptosystem that encrypts a plaintext with a secret circulant matrix and transmits the ciphertext over a wireless channel. The relative entropy is considered as a security measure for the indistinguishability of the CS-based cryptosystem. By developing an upper bound on the entropy, the security analysis reveals that the presence of wireless channels and additive noise contributes to reducing the relative entropy of the cryptosystem. Consequently, the CS-based cryptosystem with circulant matrices can guarantee wireless security in terms of the indistinguishability, as long as the channel gains and the plaintext-to-noise power ratio of an adversary are kept to be low for a long keystream and a short ciphertext.

In this study, an encryption algorithm that uses chaos based S-BOX is developed for secure and speed image encryption. First of all, a new chaotic system is developed for creating S-Box and image encryption algorithm. Chaos based random number generator is designed with the help of the new chaotic system. Then, NIST tests are run on generated random numbers to verify randomness. A new S-Box design algorithm is developed to create the chaos based S-Box to be utilized in encryption algorithm and performance tests are made. As the next step, the new developed S-Box based image encryption algorithm is introduced in detail. Finally, image encryption application is carried out. To show the quality and strong of the encryption process, security analysis are performed. Proposed algorithm is compared with the AES and chaos algorithms. According to tests results, the proposed image encryption algorithm is secure and speed for image encryption application. (C) 2016 Elsevier Ltd. All rights reserved.

In order to construct efficient public-key encryption scheme that is secure against adaptive chosen-ciphertext attacks (CCA), an efficient signature scheme and an identity-based encryption (IBE) scheme from the learning with errors over rings are presented firstly in this paper, whose security are reducible to the hardness of the shortest vector problem in the worst case on ideal lattices. Secondly, a CCA-secure public key cryptosystem is constructed on the basis of the IBE and signature proposed above. The efficiency analysis indicates the proposed signature and encryption schemes are much more efficient than correlative cryptosystems. The security analysis shows that the IBE scheme is secure against chosen-plaintext attacks, and the public-key encryption scheme is CCA-secure in the random oracle model.

Shor proposed a quantum polynomial-time integer factorization algorithm to break the RSA public-key cryptosystem. In this paper, we propose a new quantum algorithm for breaking RSA by computing the order of the RSA ciphertext C. The new algorithm has the following properties: 1) recovering the RSA plaintext M from the ciphertext C without factoring n; 2) avoiding the even order of the element; 3) having higher success probability than Shor’s; 4) having the same complexity as Shor’s.

Attributed-based encryption (ABE) is a promising cryptographic access control mechanism with a rich expressiveness of ABE policies. Due to the high complexities of encryption and decryption, users are burdened with large computation cost. Fortunately, outsourcing technologies can be used to reduce the computation overhead for the ABE schemes. In the recent decade, the achievements of the outsourced ciphertext-policy ABE (CP-ABE) schemes are inspiring. But, the outsourcing encryption algorithms for CP-ABE schemes are not addressed properly since the encryption exponents are dynamic. In this paper, we present an efficient outsourced CP-ABE scheme with checkability, where the number of the exponential operations in the encryption can be reduced to a constant by introducing a blinding algorithm. Meanwhile, the ciphertext size is not increased. Furthermore, to guarantee the correctness of our scheme, we provide the verification mechanism based on a collision-resistance hash function, which allows the users to efficiently check the validity of messages and outsourced computation results. Besides, the proposed scheme is secure against replayable chosen ciphertext attacks based on Green’s outsourcing security model. Intensive experiments are carried out to illustrate the efficiency of the proposed scheme.

Subspace membership encryption is a generalization of inner product encryptions, which was recently formalized by Boneh, Raghunathan, and Segev in Asiacrypt 2013. The construction of this new predicate encryption was motivated by the fact that traditional predicate encryptions did not yield function privacy, a security notion introduced by Boneh et al. in Crypto 2013. This newly defined security notion requires that no information on the predicate associated to a given secret key is revealed, beyond the absolute minimum necessary. Boneh et al. gave a generic construction of the subspace membership encryption based on any inner product encryption. However, our research shows that their construction for subspace membership encryptions when the attribute space is small was incorrect, and that it does not yield the attribute hiding security, which is the baseline notion of security for predicate encryptions. In this paper, we will first show why the construction does not possess the attribute hiding security, and see that this can not be altered through simple reconstruction. Then, we will formulate a generalized construction of subspace membership encryptions by introducing probability distributions over the attribute and predicate space, and prove that the attribute hiding security can not be satisfied even in the generalized setting. We will consider the requirements for subspace membership encryptions to yield the attribute hiding security, and evaluate them probabilistically. Finally, we will present an extension of our generalized construction, and show that it holds the attribute hiding security even in small attribute spaces. However, in our extended generalized construction, function privacy was deprived, which was precisely the motivation of formalizing subspace member encryptions in the first place. Although, we did not succeed in constructing a subspace membership encryption which both yields the attribute hiding security and function privacy, we formalized a richer framework of construction of subspace membership encryptions, and discovered a trade-off like relationship between the two security notions, which presents possibility for a construction in-between ours and Boneh et al.’s. Furthermore, our extended generalized construction cuts open new perspectives in the construction of subspace membership encryptions and enables us to make various choices on the underlying inner product encryptions.

In this paper, we introduce a new family of lattices, namely QC-MDPC lattices, which are a special case of LDPC lattices, and an improved bit flipping algorithm for decoding of these lattices. Encoding and decoding implementations of QC-MDPC lattices are practical in high dimensions. Indeed, to take advantage of practical decoding, we use “Construction-A”lattices which makes a tight connection between the structure of lattices and codes. Using these features, we design a lattice-based public key encryption scheme enjoying linear encryption and decryption complexities. The proposed scheme has a reasonable key size due to the sparseness of the parity-check matrix, and the quasi-cyclic structure of the parity-check and generator matrices. Besides, the message expansion of the proposed scheme is smaller than other lattice-based and code-based cryptosystems with comparative parameters. All these features provide a lattice-based public key encryption scheme with reasonable key size, linear encryption, and decryption algorithms and small message expansion. On the other hand, we show that the cryptosystem is resistant against all known attacks both on lattice-based and code-based cryptosystems for different levels of security.

The paradigm of forward security provides a promising approach to deal with the key exposure problem as it can effectively minimize the damage caused by the key exposure. In this paper, we develop a new forward-secure identity-based encryption scheme without random oracles. We formally prove that the proposed scheme is secure against adaptive chosen-ciphertext attacks in the standard model. In the proposed scheme, the running time of the private key extraction and decryption algorithms and the sizes of the user's initial private key and the ciphertext are independent on the total number of time periods, and any other performance parameter has at most log-squared complexity in terms of the total number of time periods. Compared with the previous forward-secure identity-based encryption schemes, the proposed scheme enjoys obvious advantage in the overall performance. To the best of our knowledge, it is the first forward-secure identity-based encryption scheme that achieves direct chosen-ciphertext security in the standard model.

In this paper, a new chaos-based partial image encryption scheme based on Substitution-boxes (S-box) constructed by chaotic system and Linear Fractional Transform (LFT) is proposed. It encrypts only the requisite parts of the sensitive information in Lifting-Wavelet Transform (LWT) frequency domain based on hybrid of chaotic maps and a new S-box. In the proposed encryption scheme, the characteristics of confusion and diffusion are accomplished in three phases: block permutation, substitution, and diffusion. Then, we used dynamic keys instead of fixed keys used in other approaches, to control the encryption process and make any attack impossible. The new S-box was constructed by mixing of chaotic map and LFT to insure the high confidentiality in the inner encryption of the proposed approach. In addition, the hybrid compound of S-box and chaotic systems strengthened the whole encryption performance and enlarged the key space required to resist the brute force attacks. Extensive experiments were conducted to evaluate the security and efficiency of the proposed approach. In comparison with previous schemes, the proposed cryptosystem scheme showed high performances and great potential for prominent prevalence in cryptographic applications.

Dual receiver encryption (DRE) allows two independent receivers to decrypt a ciphertext into a same plaintext. Aiming at solving the dilemma of DRE in the traditional PKE settings, this paper gives an identity‐based variant version of DRE: identity‐based dual receiver encryption (ID‐DRE). Based on Waters' IBE, two concrete ID‐DRE constructions are given in the standard model. Moreover, adopting a random walk‐like methodology also results in better security tightness for Waters' IBE, which is consistent with Hofheinz and Kiltz's result (Crypto'08).

In this paper, we have developed a new ElGamal-like public key cryptosystem based on the matrices over a groupring. The underlying hard problem for this cryptosystem is the conjugacy search problem. That is, we have replaced the exponentiation of elements by conjugacy. This makes the key generation step more efficient. We also talk about different security aspects against known attacks. The proposed scheme is found to be secure against known plaintext attack when encryption uses a different random key for every new plaintext.

We give generic constructions of several fundamental cryptographic primitives based on a new encryption primitive that combines circular security for bit encryption with the so-called reproducibility property (Bellare et al. PKC 2003). At the heart of our constructions is a novel technique which gives a way of de-randomizing reproducible public-key bit-encryption schemes and also a way of reducing one-wayness conditions of a constructed trapdoor-function family (TDF) to circular security of the base scheme. The main primitives that we build from our encryption primitive include k-wise one-way TDFs (Rosen and Segev TCC 2009), CCA2-secure encryption and deterministic encryption. Our results demonstrate a new set of applications of circularly-secure encryption beyond fully-homomorphic encryption and symbolic soundness. Finally, we show the plausibility of our assumptions by showing that the DDH-based circularly-secure scheme of Boneh et al. (Crypto 2008) and the subgroup indistinguishability based scheme of Brakerski and Goldwasser (Crypto 2010) are both reproducible.

An amplitude-phase retrieval attack free encryption scheme is proposed by using two random masks, where one is considered as the random image and other as the public key. Initially, the random image is encrypted to two phase-only masks based on interference technique with the help of the public key. These two phase-only masks are real-valued functions and used as the encryption keys. Then, the plain image is encrypted to the ciphertext with the white noise distribution by using the phase-truncated Fourier-transform-based encoding scheme with the previous encryption keys. The encryption process is nonlinear in which no iterative calculation is involved, while the decryption process is linear which can be easily implemented with the 4 f optical system. Moreover, less constraints makes the specific attack unusable. Simulation results are given to verify the feasibility and robustness of the proposed encryption scheme.

Recently a parallel sub-image encryption method is proposed by Mirzaei et al., which is based on a total shuffling and parallel encryption algorithm. In this paper, we firstly show that the method can be attacked by chosen plaintext attack and then propose an enhanced sub-image algorithm, which can completely resist the chosen plaintext attack. Moreover, our improved algorithm can reduce the encryption time dramatically. The experimental results also prove that the improved encryption algorithm is secure enough. So the improved method can be used in image transmission system.

This article presents a novel cryptosystem for secure transmission of color images through a coordinate cryptosystem as well as a geometric cryptosystem with time domain and frequency domain. In this technique, we have designed image encryption and decryption by a proposed random matrix shift cipher (RMSC) associated with a discrete fractional Fourier transform (DFrFT). Our proposed random matrix shift cipher is a coordinate and geometric cryptosystem for security of color image data which is completely different from existing cryptosystems for security of any data. The combination of a random matrix shift cipher and discrete fractional Fourier transform provide a robust cryptosystem for color image data in the time domain as well as the frequency domain without loss of any information. Existing techniques provide single-layer protection of color image data, but the cryptosystem presented here gives multiple layers of protection. Computer simulation on a standard example (Lena and Barbara color im...

In this paper, a novel image encryption approach based on permutation-substitution (SP) network and chaotic systems is proposed. It consists of four cryptographic phases: diffusion, substitution, diffusion and permutation. Firstly, a diffusion phase is proposed based on new chaotic map. Then, a substitution phase based on strong S-boxes followed by a diffusion phase based on chaotic logistic map are presented which will, in turn, significantly increase the encryption performance. Finally, a block permutation phase is accomplished by a permutation function to enhance the statistical performance of the proposed encryption approach. Conducted experiments based on various types of differential and statistical analyses show that the proposed encryption approach has high security, sensitivity and speed compared to previous approaches A novel image encryption approach based on SP network and chaos is proposed.Qualitative and quantitative analysis verify the effectiveness of the proposed encryption scheme.The encryption scheme shows superior performance than previous schemes.

In CRYPTO'13, Gentry et al. proposed the first homomorphic encryption HE scheme for the attribute-based encryption ABE. However, Gentry's scheme requires the same index for encryption of each ciphertext and supports only the key-policy ABE. Indeed, in SECRYPT'13, Clear et al. left an open problem in the Gentry et al. scheme viz. a scheme that requires different sets of index in HE using ABE and supports the ciphertext-policy ABE CP-ABE, where the sender is assumed to be intelligent. In addition, in INDOCRYPT'12, Vaikuntanathan discussed an open problem viz. to work out the HE using cryptographic techniques other than lattice-based cryptography. With an aim to propose the CP-ABE scheme using HE, in this research attempt, we propose an approach that integrates the benefits of HE in CP-ABE and yet uses pairing-based cryptography. In our approach viz. attribute-based HE AB-HE, a user is able to successfully decrypt the ciphertext only if the attributes in the policy match those in the secret key. However, in addition, our approach also allows multiple invocations of multiplication operation on the ciphertext as in a typical partially HE, coupling the advantages of the partial HE in the CP-ABE. Further, we also propose an extension of the proposed scheme that serves as a pseudo-fully HE, but requires the help of a key authority. The security of the proposed scheme is based on the decisional bilinear Diffie-Hellman problem. To the best of our knowledge, ours is a unique attempt in integrating HE into the attribute-based cryptography with different indexes/policies. In addition, our AB-HE scheme is pairing-based, and by adding more ciphertexts, it does not blow the final ciphertext size because we use the constant length ciphertext approach for the encryption. Copyright © 2016 John Wiley & Sons, Ltd.