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ABKS has drawn much attention from research and industry in recent years, an ABKS scheme is an encryption scheme that supports keyword search and access control. Attribute-Based Encryption is a public key encryption that enables users to encrypt and decrypt message based on attributes. In a typical implementation, the size of the ciphertext is proportional to the number of attributes associated with it and the decryption time is proportional to the number of attributes used during decryption. Inherit from ABE technology, the computation cost and ciphertext size in most ABKS schemes grow with the complexity of the access policy. On the other hand, we found that the traditional ABKS schemes cannot resist our secret-key-recovery attack. To deal with the above problems, we present new ciphertext policy attribute based encryption with fast keyword search constructions. Our constructions preserve the fine-grained access control inherited from the ABE system while supporting hidden policy and fast keyword search. Our constructions feature multi-value-independent compared with the existing attribute based searchable encryption schemes. The performance analysis demonstrates the efficiency of our constructions. We offer rigorous security proof of our second scheme, which is IND-CKA and IND-CPA secure.

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

The study of sending and receiving secret messages is called cryptography. Generally, senders and receivers are unaware about the process of encryption and decryption. Hence, encryption plays an important role in data communication and data security. The meaning of encryption is not only to keep data confidential from unwanted access but also ensuring the data integrity through available way. As the capacity of breaking the security is increasing rapidly, so, the process that hides information is one of the most concerned topics. Advanced Encryption Standard is a popular, widely used and efficient encryption algorithm, which has been used since it was invented. This paper focuses on the AES key generation process and Substitution box. It modifies the conventional key generation technique and builds the dynamic 3-Dimensional S-box of Advance Encryption Standard. The proposed approach suggests 3-Dimensioanl Key Generation Matrix and S-box. As per shown this novel technique increases the amount of time it needs during encryption and decryption. The experimental result shows that it also enhances the strength of AES algorithm. The proposed approach illustrates the theoretical analysis and corresponding experimented results., 7 pages, 14 figures, 4 tables. Published in IJCSA in 2017

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.

This paper presents the weaknesses in the cryptosystem proposed by W. Zhang and his colleagues. The proposed method to restore the permutation rule is based on the chosen-ciphertext attack. The method is successful in restoration of the permutation rule in the case of multiple encryption rounds without any knowledge about the cryptosystem. In order to improve the security of W. Zhang's cryptosystem, the proposed modifications are made to the equations to resist against the chosen-ciphertext attack. The specific examples will demonstrate the cryptanalysis and the security improvement.

As there is rapid revolution in digital multimedia which is in compressed encrypted format, the ability for creating similar and unauthorized data, that can be easily copied, manipulated and distributed has been increased. Hence for copyright management protection, ownership identification, tamper detection and for other security issues watermarking has to be carried out for tamper proofing, quality assessment and copy control for those media content. Thus there is a need for an encryption scheme which could provide security as well as allow us to watermarking these compressed encrypted data. For encryption we propose a stream cipher called Modified Rivest Cipher 4 that overcome several weaknesses of the RC4. The embedding capacity, robustness, perceptual quality and security of the proposed algorithm, using the watermarking schemes: spread spectrum, scalar costa scheme quantization index modulation has been proposed and the comparison based on PSNR, MSE and BER values has been done between various encryption algorithms.

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.

The paper proposes a secure audio cryptosystem that realize integrity, authentication and confidentiality. The proposed audio cryptosystem achieves integrity by applying a message digest algorithm, authentication by employing LSB watermarking and confidentiality through encryption with Advanced Encryption Standard (AES) or RC6. The main concept of the proposed audio cryptosystem relays on XORing the plain-audio with one selected image from a private image database. Then, the mixed plain-audio blocks are LSB watermarked with the selected image hash value prior to ciphering. The proposed audio cryptosystem is prepared with the potential of increasing immunity against brute force attacks and providing integrity, authentication and confidentiality through the selected image hash value addition using LSB embedding as an extra key. Also, the extra XORing step removes residual intelligibility from the plain-audio blocks, fills the speechless intervals of audio conversation and helps in destroying format and pitch information. The proposed audio cryptosystem is compared with audio encryption using AES, and RC6 through encryption key performance indicators. The comparison outcomes ensured the superiority of the proposed audio cryptosystem. Security investigation of the proposed audio cryptosystem is studied from a precise cryptographic standpoint and tests ensured the superiority of the proposed audio cryptosystem from a cryptographic standpoint.

Elliptic curve analogue ElGamal encryption scheme requires encoding of the plain message onto elliptic curve coordinate using Koblitz encoding technique before encryption operation. The paper proposes a medical image encryption scheme using improved ElGamal encryption technique. A new finding has been made in the proposed method where separate calculations for encoding plain message to elliptic curve coordinate is removed. The algorithm in the improved version of ElGamal encryption scheme is designed to encrypt medical image where data expansion issue is resolved and execution speed is enhanced. The strength of the proposed method is insured through various statistical and security analyses and comparison with other existing encryption schemes.

We propose a modified optical asymmetric cryptosystem based on coherent superposition and equal modulus decomposition (EMD). In the encryption process, the asymmetric cells of the previous cryptosystem is cascaded, while some small changes are made. In the first cell, only one mask, whose phase is not equal with the public key, is generated to be used as the input of the second cell. As a consequence, the modified cryptosystem decreases available constrain conditions for attackers, resulting in a high robustness of the cryptosystem against the attack based on iterative Fourier transform. Furthermore, the modified scheme maintains the good performance of our previous cryptosystem, especially the benefit of key management. Some numerical simulations are presented to verify the validity and the performance of the modified cryptosystem.

A robust encryption algorithm using DNA and chaotic logistic maps was recently proposed, which can resist exhaustive attack, statistical attack and differential attack. The security of this encryption algorithm depends on the initial conditions of 1D and 2D logistic chaotic maps, which include the front and latter pixel sum of plain image. However, this scheme is not secure enough because the front half and latter half pixel sum can be known to the attacker. According to this security weakness the encryption algorithm is completely cracked by a novel chosen-plaintext attack scheme. Experiments and analysis verify our approach.

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.

The design of a Homomorphic Encryption (HE) algorithm that allows computation over the encrypted data is required in real world modern applications to preserve the privacy. Such applications include Cloud Computing, shared storage, processing resources, etc. The existing solutions are not practical for real world applications. Asymmetric approaches suffer from high computation overhead, while symmetric approaches suffer from low immunity against attacks such as chosen and known plaintext attack. In this paper, we consider symmetric approaches and we focus on Matrix Operation for Randomization and Encryption (MORE) approach to build a new algorithm overcoming the drawbacks of MORE. The proposed algorithm is explained in details and evaluated. The security performance results show that the proposed approach can prevent the strong attacks without degradation of the system performances in term of latency and energy consumption.

In recent years, researchers have been focused on the optical asymmetric cryptosystem (OACS). The encryption key and decryption key are independent, the fact of which overcomes the linearity defect of optical encryption system. So the OACS has attracted more and more researchers’ attention. We have deeply studied the existing OACS, and found that the cryptosystem is unable to realize communication in practice. In this paper, we demonstrate the shortcomings of the present OACS and propose a practical scheme. The analysis shows that this scheme meets the communication protocol of asymmetric cryptography (ACS).

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.

Recently, a novel image fusion encryption algorithm based on DNA sequence operation and hyper-chaotic system were proposed. It was reported that the encryption algorithm can be broken by chosen-plaintext attack. This paper re-evaluates the security of the encryption algorithm, and finds that the encryption algorithm can be broken by known-plaintext attack as well. Besides, it also gives another method of chosen-plaintext attack which is more effective. The effectiveness of the proposed know-plaintext attack and chosen-plaintext attack is supported both by rigorous theoretical analysis and experimental results.

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 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.

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.

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.

This paper introduces a secure speech communication approach, which is based on encryption and authentication. This system is based on Advanced Encryption Standard (AES) for encryption and private image database for enhancement of encryption and for authentication. The idea of this cryptosystem is based on XOR of one image from image database with the clear speech before encryption and embedding the index number of this image in the database as a least significant bit watermark into speech. A comparison study is held between the AES block cipher algorithm and the proposed algorithm. This proposed cryptosystem used to enhance the security of AES algorithm and increase its immunity to brute force attacks. It used also to provide authentication and enhance security by addition of extra key which don't need to be exchanged between parts depending on the embedded image. The extra proposed step remove residual intelligibility from clear speech and fill the silent periods within speech conversation and help in destroy format and pitch information. Security analyses are presented for the proposed cryptosystem from a strict cryptographic viewpoint. Experimental results verify and prove that the proposed cryptosystem is highly secure from the cryptographic viewpoint.

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.

Fog computing is a paradigm that extends cloud computing to the edge of the network. It can provide computation and storage services to end devices in Internet of Things (IoT). Attribute-based cryptography is a well-known technology to guarantee data confidentiality and fine-grained data access control. However, its computational cost in encryption and decryption phase is linear with the complexity of policy. In this paper, we propose a secure and fine-grained data access control scheme with ciphertext update and computation outsourcing in fog computing for IoT. The sensitive data of data owner are first encrypted using attribute-based encryption with multiple policies and then outsourced to cloud storage. Hence, the user whose attributes satisfy the access policy can decrypt the ciphertext. Based on the attribute-based signature technique, authorized user whose attributes integrated in the signature satisfy the update policy can renew the ciphertext. Specifically, most of the encryption, decryption, and signing computations are outsourced from end devices to fog nodes, and thus, the computations for data owners to encrypt, end users to decrypt, re-encrypt, and sign are irrelevant to the number of attributes in the policies. The security analysis shows that the proposed scheme is secure against known attacks, and the experimental results show that the fog nodes perform most of the computation operations of encryption, decryption, and signing, and hence, the time of encryption for data owner, decryption, re-encryption, and signing for users is small and constant.

Cyber Security has become rising issue in recent years where encryption is one of solution and has an important role in data protection. Encryption algorithms that widely used in information security are asymmetric and symmetric. Advanced Encryption Standard (AES) is one of symmetric encryption that most used often and the most secure encryption today. However, AES encryption has slow computation. Our experiment show that both of algorithms combination needs 3.045 milliseconds for 1024 bytes of data and increase 3-4 milliseconds for 2048 bytes of data and so on. This paper proposes a novelty method to improve AES algorithm with Shift Row and S.Box modification for Mix Column transformation. The result show that our optimization has reduced 3 milliseconds and continue to increase as the number of bytes increases. Percentage average of the optimization is 86.143%.

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, 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.

Recently, a chaotic encryption algorithm for highly autocorrelated data was proposed. By adding chaotic diffusion to the former work, the information leakage of the encryption results especially for the images with lower gray scales was eliminated, and both higher-level security and fast encryption time were achieved. In this study, we analyze the security weakness of this scheme. By applying the ciphertext-only attack, the encrypted image can be restored into the substituted image except for the first block; and then, by using the chosen-plaintext attack, the S-boxes, the distribution map, and the block of chaotic map values, can all be revealed, and the encrypted image can be completely cracked. The improvement is also proposed. Experimental results verify our assertion.

The notion of selective opening attacks (SOAs) was first introduced by Dwork et al. at FOCS'99. Informally, an encryption scheme is SOA secure if an adversary is given a vector of ciphertexts and can adaptively corrupt some fraction of them by obtaining not only their messages but also their randomness, the uncorrupted ciphertexts retain secure. Provably achieving security against SOA has been proven extremely challenging. In this paper, we propose a security model to capture simulation-based selective opening chosen-plaintext attacks (SIM-SO-CPA) for certificateless encryption. We provide a concrete construction and prove its security in our simulation-based selective opening chosen-plaintext attack security model, based on the real or random and computational Diffie–Hellman assumptions. Compared with previous SOA-secure public key encryption and identity-based encryption, our certificateless encryption scheme is more simple and efficient. Copyright © 2017 John Wiley & Sons, Ltd.

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).

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 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.

Traditional cipher systems are not appropriate for video encryption due to the high computation overhead. Video encryption must take account of the trade-off of both data security and real-time performance. In this paper, an efficient chaos pseudo-random number generator is designed to generate key stream for encrypting video syntax elements of H.264/AVC. In view of the efficiency and security, the intra-prediction mode (IPM), signs of trailing ones (T1s), signs of non-zero (NZ) coefficients, signs of motion vector difference (MVD) are chosen for selective encryption. The proposed scheme provides sufficient protection for the video commercial value. Experimental results demonstrate that the course of encryption will not affect the coding efficiency of H.264/AVC by keeping exactly the same bitrate and negligible time overhead. Security analysis shows that the proposed scheme has the ability to resist malicious attacks.

Proxy re-encryption (PRE) enables an authorized proxy to convert a ciphertext under Alice's public key into a ciphertext under Bob's public key without exposing the encrypted message. In existing PRE systems, the original ciphertexts and the re-encrypted ones are both required to be in the same cryptosystem, which limits their applications in cloud computing systems. In this paper, we propose a new proxy re-encryption pattern, referred to as an identity-based proxy re-encryption version 2 (IBPRE2). It allows an authorized proxy to convert a ciphertext of an identity-based broadcast encryption (IBBE) scheme into a ciphertext of an identity-based encryption (IBE) scheme. With IBPRE2, one can take advantage of IBBE to securely share data with a set of recipients, and then incorporate an additional one into the authorized set through the re-encryption mechanism, without decrypting the IBBE ciphertext nor leaking any sensitive information. We formalize the security requirements in IBPRE2 and propose a provably CCA-secure scheme. The unique feature of ciphertext transformation from a complicated cryptosystem to a simple one makes our IBPRE2 a versatile cryptographic tool to secure outsourced data in cloud computing. We propose a framework of identity-based proxy re-encryption (IBPRE2) system for cloud computing.We formally define the CCA (chosen-ciphertext attack) security of the IBPRE2.We construct an IBPRE2 scheme and prove its CCA-security assuming that the underlying cryptographic primitives are secure.

Recently, an image encryption algorithm based on hyper-chaotic system and dynamic S-box has been proposed by Liu et al. The main idea of the encryption algorithm is utilizing key-streams generated by hyper-chaotic system to permute and substitute plain-image pixels. In this paper, we analyze the potential security problems of the encryption algorithm in detail and propose a chosen-plaintext attack to break the encryption algorithm. The proposed chosen-plaintext attack indicates that the encryption scheme is insecure and not suitable for image secure communication. Based on the result of cryptanalysis, an improved algorithm is proposed to eliminate the potential security problem in Liu’s algorithm. Experimental results show that improved algorithm not only inherits the merits of the original scheme, but also has better cryptographic performances in statistical characteristics, plaintext sensitivity and key sensitivity.

A novel image encryption system based on double random phase encoding (DRPE) and RSA public-key algorithm is proposed. The main characteristic of the system is that each encryption process produces a new decryption key (even for the same plaintext), thus the encryption system conforms to the feature of the one-time pad (OTP) cryptography. The other characteristic of the system is the use of fingerprint key. Only with the rightful authorization will the true decryption be obtained, otherwise the decryption will result in noisy images. So the proposed system can be used to determine whether the ciphertext is falsified by attackers. In addition, the system conforms to the basic agreement of asymmetric cryptosystem (ACS) due to the combination with the RSA public-key algorithm. The simulation results show that the encryption scheme has high robustness against the existing attacks.

This paper is a cryptanalysis of a recent proposed image encryption algorithm based on chaotic functions. The cryptosystem is composed of two-stage permutation and one-stage substitution for encryption of the gray scale plain-image. However, by applying chosen plaintext attack which is described in this paper, we show that all the secret parameters can be revealed. In addition, some other security defects of the cryptosystem are also highlighted. Both mathematical analysis and experimental results confirm the feasibility of this attack. As a result, the cryptosystem in this structure cannot be recommended when we need a higher level of security.

Ciphertext-policy attribute-based encryption (CP-ABE) has been a preferred encryption technology to solve the challenging problem of secure data sharing in cloud computing. The shared data files generally have the characteristic of multilevel hierarchy, particularly in the area of healthcare and the military. However, the hierarchy structure of shared files has not been explored in CP-ABE. In this paper, an efficient file hierarchy attribute-based encryption scheme is proposed in cloud computing. The layered access structures are integrated into a single access structure, and then, the hierarchical files are encrypted with the integrated access structure. The ciphertext components related to attributes could be shared by the files. Therefore, both ciphertext storage and time cost of encryption are saved. Moreover, the proposed scheme is proved to be secure under the standard assumption. Experimental simulation shows that the proposed scheme is highly efficient in terms of encryption and decryption. With the number of the files increasing, the advantages of our scheme become more and more conspicuous.