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

Recently, an image encryption scheme based on a 2D hyperchaotic map is proposed. It adopts the permutation–diffusion architecture and consists of three steps, which are permutation, forward diffusion, and backward diffusion. In this paper, we break this cipher with both the chosen-plaintext attack (CPA) and the chosen-ciphertext attack (CCA). According to our analysis, we found the two complex diffusion processes could be simplified into two simple diffusions and a modular addition operation. Based on this, the equivalent key can be obtained with CPA and CCA. Detailed theoretical derivations and the results of experiments confirmed the feasibility of our attack methods. When the image size was 256×256, the running time of the attacks was less than 2 hours on a laptop with a 2.59 GHz Intel Core i7 and 16 GB DDR3 memory. Other sizes of images were also tested, and some rules were found. In addition, the probability of other attacks has also been discussed, and some suggestions for improvements are given. The source codes are publicly available and can be found online.

The Rao-Nam cryptosystem is a symmetric version of the McEliece code-based cryptosystem proposed to get rid of the shortcomings inherent in the first symmetric code-based encryption schemes. Almost immediately after the publication of this cryptosystem, attacks on it based on selected plaintexts appeared, which led to the emergence of various improvements and modifications of the original cryptosystem. The secret key in the traditional Rao-Nam scheme is a certain Boolean matrix and a set of binary vectors used to generate distortions during encryption. Such vectors must have different syndromes, that is, be different modulo of the code generated by the rows of the specified matrix. The original work of Rao and Nam considered two methods of forming the set of these vectors, the first of which consists in using predetermined vectors of sufficiently large weight, and the second is random selection of these vectors according to the equiprobable scheme. It is known that the first option does not provide the proper security of the Rao – Nam cryptosystem (due to the small number and simple structure of these vectors), but the second option is more meaningful and requires additional research. The purpose of this paper is to obtain estimates of the effectiveness (time complexity for a given upper bound of the error probability) of attacks on a cryptosystem, which generalizes the traditional Rao – Nam scheme to the case of a finite Abelian group (note that the need to study such versions of the Rao – Nam cryptosystem is due to their consideration in recent publications). Two attacks, based on selected plaintext, are presented. The first of them is not mentioned in the works known to the authors of this article and, under certain well-defined conditions, it allows recovering the secret key of the cryptosystem with quadratic complexity. The second attack is a generalized and simplified version of the well-known Struik-van Tilburg attack. It is shown that the complexity of this attack depends on the power of the stabilizer of the set of vectors, which forms the second part of the key, in the translation group of the Abelian group, over which the Rao – Nam cryptosystem is considered. In this paper, a bound is obtained for the probability of triviality of the stabilizer under the condition of random choice of this set. From the obtained bound, it follows that Struik-van Tilburg attack is, on average, noticeably more efficient than the worst case considered earlier.

Image encryption converts the images into unrecognizable forms that seems like a white noise. Digital Chaos has also emerged as one of the important technique to design secure and efficient image encryption schemes. The chaos theory possesses various desirable properties required for the encrypting images like initial state sensitivity, unpredictability and behavioural complexity. However, image encryption schemes suffer from vulnerabilities like differential attack, statistical, known/chosen plaintext attack, and brute force attack. This paper proposes a novel approach to generate a pseudorandom key. This pseudo random key is combined with Logistic map (LM), cosine transformed Logistic map (CTLM) and cosine transformed Logistic-Sine Map (CTLSM), one by one, to implement three secure and efficient methods for satellite image encryption. The scheme uses the 384-bit of share key to perform encryption during the process. The proposed approaches are tested for parameters such as Entropy, Correlation Coefficient (CC), Number of Changing Pixel Rate (NPCR), Unified Averaged Changed Intensity (UACI), Avalanche effect, Bit Correct Ratio (BCR) and Peak Signal to Noise Ratio (PSNR). The work also analyses the various cryptanalytic attacks on the proposed chaos and novel Pseudo random key combinations. The results show that the proposed pseudo random key and CTLSM combination outperforms the other two combinations, and is more efficient in resisting all type of attacks as well.

This article proposes a hybrid certificateless signcryption scheme that is secure against adaptive chosen ciphertext adversary in the random oracle model. The scheme combines an asymmetric encryption which is one way against chosen plaintext attack and any One-Time secure symmetric encryption scheme, combined using Fujisaki–Okamoto transformation. Uncommon to many Fujisaki–Okamoto based constructions which ensure message integrity alone, this scheme provides entity authentication in addition. By the choice of a hash function that utilizes the advantage of sponge based construction, the scheme enables the user to incorporate any One-Time secure symmetric encryption by re-configuring the input/output parameters. Fujisaki–Okamoto transformation, which is currently a standard in hybrid constructions, guarantees the indistinguishability against adaptive chosen ciphertext attack. The provision for choosing symmetric encryption in the scheme enables it to be implemented in all sort of cryptographic requirements including those in wireless communication.

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

Ciphertext-policy attribute-based searchable encryption (CP-ABSE) is widely used in the cloud environment to provide data privacy and fine-grained access control over encrypted data. The existing CP-ABSE schemes are designed based on bilinear pairing hardness assumptions to prove their security. However, these schemes are vulnerable to quantum attacks, i.e., adversaries can break the security of these schemes with the use of quantum computers. To address this issue, in this paper, we propose a novel ciphertext-policy attribute-based searchable encryption from lattice (CP-ABSEL) in cloud storage, since lattice-based cryptography is quantum attacks free. In CP-ABSEL, we adopted learning with errors (LWE) hardness assumption to resist from quantum attacks. Further, CP-ABSEL is indistinguishable against the chosen keyword attack and indistinguishable against chosen plaintext attack. Moreover, CP-ABSEL allows only legitimate users to perform a keyword search over an encrypted index, and unauthorized users cannot get even the ciphertext form of documents. The performance analysis proves that CP-ABSEL is efficient and practical.

In current years many chaos-based Substitution boxes (S-boxes) have been proposed. Recently, an image encryption technique based on multiple chaotic S-box was offered. This encryption method was based on the concept of confusion only produced by the implementation of the S-box. The concept of confusion utilized in the understudy technique can be smashed by using just one chosen-plaintext attack and a chosen-ciphertext attack. This article presents a detailed structure of two types of cryptographic attacks on the diffusion-based encryption scheme. The proposed attacks are successfully performed to retrieve the key with very little execution time by using just one chosen image which indicates the vulnerability of multiple chaotic S-boxes-based cryptosystems. The retrieved data is passed through some statistical analysis such as correlation, histogram, and entropy to check the correctness of recovered data.

As is known, attribute-based encryption (ABE) is usually adopted for cloud storage, both for its achievement of fine-grained access control over data, and for its guarantee of data confidentiality. Nevertheless, single-authority attribute-based encryption (SA-ABE) has its obvious drawback in that only one attribute authority can assign the users’ attributes, enabling the data to be shared only within the management domain of the attribute authority, while rendering multiple attribute authorities unable to share the data. On the other hand, multi-authority attribute-based encryption (MA-ABE) has its advantages over SA-ABE. It can not only satisfy the need for the fine-grained access control and confidentiality of data, but also make the data shared among different multiple attribute authorities. However, existing MA-ABE schemes are unsuitable for the devices with resources-constraint, because these schemes are all based on expensive bilinear pairing. Moreover, the major challenge of MA-ABE scheme is attribute revocation. So far, many solutions in this respect are not efficient enough. In this paper, on the basis of the elliptic curves cryptography, we propose an efficient revocable multi-authority attribute-based encryption (RMA-ABE) scheme for cloud storage. The security analysis indicates that the proposed scheme satisfies indistinguishable under adaptive chosen plaintext attack assuming hardness of the decisional Diffie-Hellman problem. Compared with the other schemes, the proposed scheme gets its advantages in that it is more economical in computation and storage.

In order to improve the security and efficiency of image encryption, many researchers have continuously proposed new image encryption schemes in recent years. However, these image encryption schemes have not been fully analyzed and evaluated. In this paper, a newly reported image encryption scheme based on Feistel network and dynamic Deoxyribonucleic Acid (DNA) encoding is deeply and comprehensively investigated. This encryption scheme mainly adopts four encryption steps to encrypt the plain image, which are Generation of chaotic sequences, Hill encryption, Feistel network, and Pixel diffusion. Our analyses show that there are some problems in the secret key design and encryption process of this encryption scheme. After pointing out and analyzing these problems, we have made several necessary improvements to this encryption scheme and proposed the corresponding chosen-plaintext attack algorithm. The subsequent simulation tests and analyses have confirmed the effectiveness and feasibility of the proposed attack algorithm. Finally, for the problems in this encryption scheme and some current image encryption schemes, improvement suggestions are presented to provide references for the designers of future image encryption schemes.

Many encryption algorithms are designed to decrease the probability of cyberattacks by assuring data security as well as system and participant authentication. However, in the development of computer resources cryptanalytical techniques have been developed and performed competitively in information security with good results. In this paper, we reported security flaws in the recently offered encryption technique based on a chaotic map for Internet of Health Things (IoHT) security. The scheme was based on a new chaotic map, modified Mandelbrot set, and conditional shift algorithm asserting the encryption algorithm is secure. We have performed some cryptographic attacks to retrieve the key from the understudy cryptosystem. The key was retrieved in little computation by using a chosen-plaintext attack and one known plaintext ciphertext pair. The minimum execution time of performed attacks indicates the vulnerability of the diffusion-based encryption algorithm. To enhance the security of the understudy cryptographic algorithm, we have also suggested certain improvements.

The Internet of Things (IoT) changed our lives with huge amounts of data production. Due to source-limited IoT devices, one of the best ways to process the data is cloud storage. However, a series of security and privacy issues arise, such as illegal data access, data tampering, and privacy leak. Though symmetric encryption can guarantee data confidentiality, it cannot realize fine-grained data sharing and searching. The keyword-based searchable attribute-based encryption (KSABE) can achieve data confidentiality and fine-grained access control. More importantly, it realizes a keyword-based search for data users. However, the heavy decryption computation burden and the management of massive user keys appear when implementing attribute-based encryption schemes to IoT. Therefore, this article proposes a blockchain-aided searchable attribute-based encryption (BC-SABE) with efficient revocation and decryption, where the traditional centralized server is replaced with a decentralized blockchain system being in charge of the threshold parameter generation, key management, and user revocation. All revocation tasks are done by the blockchain and it is on longer necessary for ciphertext reencryption and key update. Moreover, users utilize the coalition blockchain to generate partial tokens. Besides, the cloud server contained in our scheme not only stores the massive encrypted data but also performs search and predecryption for users who only require one exponentiation in the group ${\mathbb {G}}$ to decrypt fully. Security analyses prove that our scheme realizes the security under the chosen plaintext attack and the chosen keyword attack. Simulations show that the decryption and token generation cost of our scheme are preferable.

This paper proposes Privacy Preserving Identity-Based Broadcast Proxy Re-encryption (P2B) — a scheme to provide privacy preserving in identity-based broadcast proxy re-encryption. P2B uses Lagrange interpolation polynomial theorem to provide privacy to identities of the receiver group of broadcasted re-encrypted ciphertext. Proxy re-encryption is an efficient solution to securely share cloud data with receivers. For sharing data with a group of receivers, the sender needs to regenerate the re-encryption key for every receiver, which leads to an overhead on the sender side. To solve the issue, identity-based proxy re-encryption is extensible to identity-based broadcast proxy re-encryption. However, the later poses a privacy issue on the receiver side, as each receiver of the receiver group needs to know the other receiver's identity. We solve the problem using the Lagrange interpolation method. We prove that our scheme is secure against chosen plaintext attack using random oracle model and it successfully hides the identities of the receivers. Finally, we implement P2B and compare it with other existing systems. It is seen that P2B reduces the decryption time by $68\%$ than recent existing Broadcast proxy re-encryption schemes and $98\%$ than the existing privacy preserving schemes.

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

In this paper, a novel two dimensional (2D) wavelength/time (W/T) optical code division multiple access (OCDMA) code with zero cross-correlation property to minimize multiple access interface (MAI) is addressed. The code is constructed using various features of two different one-dimensional codes, i.e., multi-diagonal code and prime hop code referred as multi-diagonal prime hopping (MDPHC) code. The proposed 2D W/T MDPHC code is generated using java software version 8.1, which is found to be optimal. In this paper, the code complexity of the proposed 2D code is also derived. In addition to the novel 2D code design, security provision at the photonic layer of the OCDMA network is also addressed by transmitting the data through a novel encrypted circuit in order to prevent attacks by an eavesdropper. In this work, the proposed encryption circuit is integrated with the proposed 2D (W/T) MDPHC OCDMA encoder to enhance the overall security performance. The proposed model is validated using optisystem software version 14. Robustness of the proposed technique against different types of attacks such as ciphertext-only attack, known plain text attack, chosen plaintext attack, energy detection attack in on off keying optical code division multiple access, Brute-force search attack is investigated theoretically. Bit error rate is also estimated for different fiber distances.

Chaotic image encryption has been greatly investigated in recent years. However, a considerable number of the encryption schemes had been cracked by chosen plaintext attack (CPA). Although the new proposed plaintext-related chaotic image encryption schemes can resist CPA effectively, the emerged key management problem is a hot potato. In this paper, a novel fingerprint-related chaotic image encryption scheme is proposed. The generation of key streams is affected by the fingerprints of distributors rather than the plaintexts of images. In addition, the blockchain framework is adopted to ensure that the encrypted image was sent correctly form the distributor. Moreover, the distributors’ fingerprints embedded in the encrypted images are encoded by the anti-collusion code in order to record multiple fingerprints with fixed length of data. The proposed method has the following superiorities: 1) Security. CPA is invalid because the attacker does not have the fingerprint of the legal receiver. Meanwhile, no key management problem is caused. 2) Authenticity. The image, the sender and the receiver are all verified by using blockchain framework. 3) Traceability. All distributors’ fingerprints can be extracted correctly from the merged fingerprint based on the anti-collusion code, and the transmission of the image can be traced.

In terms of application of the generalized BKW algorithm, the estimates of security of Ring-LWE symmetric cryptosystem against chosen plaintext attack have been obtained. These estimates allow us to select cryptosystem parameters directly, based on its security requirements against known chosen plaintext attacks. Applicability of the generalized BKW algorithm is an important factor that affects cryptosystem security against such attacks.

In this study, a novel asymmetric image encryption scheme based on the Rivest-Shamir-Adleman (RSA) algorithm and Arnold transformation is proposed. First, the asymmetric public key RSA algorithm is used to generate the initial values for a quantum logistic map. Second, the parameters of the Arnold map are calculated. Then, Arnold scrambling operation is performed on the plain image to achieve the rough hiding of image information. Third, each row and each column of the image are taken as different units respectively and then exclusive-OR (XOR) diffusion is applied. Finally, the generated keystream is used to perform an end-to-start cyclic modulo diffusion operation for all rows and columns to produce the final cipher image. In addition, the keystream is related to the plain image, which can enhance the ability to resist chosen plaintext attack and known plaintext attack. The test results also show that the proposed encryption algorithm has strong plain sensitivity and key sensitivity.

Multimedia data, ranging from text, audio, video to animation, undergoes intellectual property protection or has high sensitivity. To deal with privacy leakage during multimedia sharing and dissemination, it is crucial to trace the origin and transformation history of multimedia data, which is called multimedia provenance. In this paper, we construct a multimedia access control system with secure provenance in fog-cloud computing networks, which is designed based on attribute based encryption (ABE) and zero of knowledge technologies. The proposed scheme realizes confidentiality of multimedia big data that is outsourced to the cloud, anonymity of data provider, fine-grained access control of encrypted data, irrefutable of the provenance data, and traceability of data provider. We utilize the fog server to reduce user’s decryption burden and transfer partial decryption tasks. The suggested system is formally proved indistinguishable against chosen plaintext attack (IND-CPA). The simulation and experimental results indicate that our system has low communication overhead and low computation cost.

A novel image authentication scheme based on two level phase retrieval algorithm (PRA) propagated in fractional Hartley transform (FrHT) to extract two phase-only masks (POMs) is proposed. PRA is based on iterative phase mask which uses nonlinear process to generate POMs which in turn makes the system immune to chosen plaintext attack (CPA) and known plaintext attack (KPA). Random amplitude mask (RAM) and random phase mask (RPM) are used as encryption keys which makes the system immune to special attack. Further multiple level of security leads to the achievement of non-convergence of MSE and good performance in the retrieval process. Apart from encrypting the information, authentication has also been included in the scheme. The features incorporated in any plaintext have been shown to provide unique signatures, which can be used to verify their authenticity. The content of the original images can be authenticated only if the authentication key is correct. The robustness of the proposed multiple level cryptosystem has been examined based on various parameters by simulating on MATLAB 9.4.0 (R2018a). The experimental results highlight the suitability and shows the attacker cannot recover the original image without the knowledge of POMs. The scheme has also been compared with similar algorithms which proves that the proposed two-level scheme is more secure, feasible and effective.