Chosen-ciphertext Research Articles

Quantum Misuse Attack on Frodo

Research on the security of lattice-based public-key encryption schemes against misuse attacks is an important part of the cryptographic assessment of the National Institute of Standards and Technology (NIST) post-quantum cryptography (PQC) standardization process. In particular, many NIST-PQC cryptosystems follow the same meta-cryptosystem. At EUROCRYPT 2019, Betu et al. mounted a classical key recovery under plaintext checking attacks (KR-PCA) and a quantum key recovery under chosen ciphertext attacks (KR-CCA). They analyzed the security of the weak version of nine submissions to NIST. In this paper, we focus on learning with error (LWE)-based FrodoPKE, whose IND-CPA security is tightly related to the hardness of plain LWE problems. We first review the meta-cryptosystem and quantum algorithm for solving quantum LWE problems. Then, we consider the case where the noise follows a discrete Gaussian distribution and recompute the success probability for quantum LWE by using Hoeffding bound. Finally, we give a quantum key recovery algorithm based on LWE under CCA attack and analyze the security of Frodo. Compared with the existing work of Betu et al., our method reduces the number of queries from to 1 with the same success probability.

Public-key encryption scheme with optimal continuous leakage resilience

In real-world applications, adversaries can launch leakage attacks, such as side-channel attacks, to obtain some information of the secret states (e.g. secret key, random value, etc.) in cryptographic protocols, compromising their security. Moreover, adversaries can obtain more leakage information by performing leakage attacks continuously, and the leakage attacks can be performed at any time by the adversary. Therefore, when designing public-key encryption (PKE) schemes, one should consider the continuous leakage setting. And it is desirable that the designed schemes can resist the leakage attacks. In this paper, to achieve better continuous leakage resilience, a novel construction of continuous leakage-resilient PKE scheme is proposed. The chosen-ciphertext attacks security of our proposed scheme can be proved based on the hardness of the decisional Diffie-Hellman assumption. Our construction tolerates a large key leakage rate, which is one of the best among existing PKE schemes. Moreover, the level of leakage resilience can be adjusted based on the specific requirements in real-world applications. The analyses demonstrate that our proposal also enjoys low computational overheads, outperforming the existing leakage-resilient PKE schemes.

Reinforced securing of data leakage in Mobile Ad hoc Network (MANET) by hybrid mechanism of identity based encryption (IBE)

In Mobile Ad hoc Network (MANET), private data leakage that involves user’s private keys may become a threat to the computing systems security. It is essential that usual requirement of traditional cryptographic patterns or mechanisms have been performed for enduring several leakage attacks. However, the attacker can track and crack the cryptographic security due to the performance of continuous leakage attacks, which assist in introducing leakage resilience cryptography. But, still there are certain issues such as data loss, data failure system, data affecting and system break that are not yet resolved. As a result, various bounded-leakage models have been created for Identity Based Encryption (IBE) constructions that fail to fulfill their stated security under continuous-leakage assaults. This paper has introduced a hybrid mechanism of security to resolve the above listed issues by focusing in avoiding continuous leakage resilient through modified IBE schemes using Adaptive Chosen Cipher-text Attacks (ACCA) with Elliptical Curve Digital Signature Algorithm (ECDSA).

On the security of fully homomorphic encryption for data privacy in Internet of Things

SummaryTo achieve data privacy in Internet of Things (IoT), fully homomorphic encryption (FHE) technique is used to encrypt the data while allowing others to compute on the encrypted data. However, there are many well‐known problems with FHE such as chosen‐ciphertext attack security and circuit privacy problem. In this article, we demonstrate that a famous FHE application named Brakerski/Fan–Vercauteren scheme, a circuit privacy application based on fast private set intersection, and an encoding application that encodes integer or floating point numbers based on Microsoft Simple Encryption Arithmetic Library homomorphic encryption library, are insecure against chosen ciphertext attacks due to insecurity of the underlying fully homomorphic schemes. These results show that using cryptographic primitives even with security proofs causes serious security vulnerabilities on the applications themselves. The results also give evidences that the security of adopted cryptographic primitives in IoT should be proved in appropriate formal security models as well as proof of the scheme itself.

RMA-CPABE : A multi-authority CPABE scheme with reduced ciphertext size for IoT devices

Internet of Things (IoT) generates a massive amount of data, which can be prone to huge data and privacy leaks unless given a proper access control. Ciphertext-policy attribute-based encryption (CP-ABE) is a well-known cryptographic mechanism that provides confidentiality and fine-grained access to stored data. In CP-ABE, a single trusted authority primarily handles attribute management and its revocation. However, in an environment like IoT, due to its heterogeneous nature, the attributes from multiple domains are evidently inherited by IoT devices and hence develop a need for a multi-authority scheme. Therefore, this paper proposes a novel multi-authority CP-ABE scheme with reduced-size ciphertext (RMA-CPABE) to provide secure access in fog-enabled IoT applications with attributes from multiple domains. This scheme considers the resource-constrained nature of IoT devices and reduces the ciphertext size in the sense that the ciphertext size does not increase linearly with the number of attributes; instead, it increases linearly with the number of multi-domain attribute authorities involved in the policy building. RMA-CPABE supports highly required functionalities like attribute update and outsourced decryption to reduce the computation load on the end devices. Further, the proposed scheme is the first to eliminate the most expensive ciphertext update operation during attribute revocation and addition, which is the biggest drawback of most of the existing schemes. The end-user in RMA-CPABE requires holding only a constant size key to access the ciphertexts securely. The security analysis proves that the proposed scheme is secure against Chosen-Ciphertext Attack (CCA) under multiple augmented Multi-Sequence of Exponents Decisional Diffie Hellman (maMSE-DDH) assumptions. The performance analysis shows that RMA-CPABE is suitable for IoT applications.

Post-Quantum Authenticated Encryption against Chosen-Ciphertext Side-Channel Attacks

Over the last years, the side-channel analysis of Post-Quantum Cryptography (PQC) candidates in the NIST standardization initiative has received increased attention. In particular, it has been shown that some post-quantum Key Encapsulation Mechanisms (KEMs) are vulnerable to Chosen-Ciphertext Side-Channel Attacks (CC-SCA). These powerful attacks target the re-encryption step in the Fujisaki-Okamoto (FO) transform, which is commonly used to achieve CCA security in such schemes. To sufficiently protect PQC KEMs on embedded devices against such a powerful CC-SCA, masking at increasingly higher order is required, which induces a considerable overhead. In this work, we propose to use a conceptually simple construction, the ΕtS KEM, that alleviates the impact of CC-SCA. It uses the Encrypt-then-Sign (EtS) paradigm introduced by Zheng at ISW ’97 and further analyzed by An, Dodis and Rabin at EUROCRYPT ’02, and instantiates a postquantum authenticated KEM in the outsider-security model. While the construction is generic, we apply it to the CRYSTALS-Kyber KEM, relying on the CRYSTALSDilithium and Falcon signature schemes. We show that a CC-SCA-protected EtS KEM version of CRYSTALS-Kyber requires less than 10% of the cycles required for the CC-SCA-protected FO-based KEM, at the cost of additional data/communication overhead. We additionally show that the cost of protecting the EtS KEM against fault injection attacks, necessarily due to the added signature verification, remains negligible compared to the large cost of masking the FO transform at higher orders. Lastly, we discuss relevant embedded use cases for our EtS KEM construction.

Lightweight ID-based broadcast signcryption for cloud–fog-assisted IoT

Balancing the security and efficiency of the internet of things (IoT) is difficult due to its numerous heterogeneous devices, different trust levels of stakeholders, and asymmetric resource distribution among layers. Identity-based broadcast encryption (IBBE) is a promising technique to ensure data confidentiality, simplify the certification management issue, and achieve one-to-many data sharing while reducing overheads simultaneously. However, broadcast encryption (BE) schemes without source authentication are not applicable in the real world as they cannot prevent invalid messages from malicious users. Meanwhile, the computation cost of IBBE is heavy and not suitable for constrained devices. This paper proposes a lightweight ID-based broadcast signcryption scheme (LIBBSC), which takes advantage of fog nodes to temporarily store ciphertext and to partially designcrypt for end users. A fog node transforms the ciphertext based on the specific user’s public identity key and then sends the outdesigncrypted ciphertext to the end-user (this step transforms the broadcast to the one-to-one communication). Finally, only the designated end-user with the associated secret key can rapidly designcrypt with minimal computational cost. Our scheme is selective-ID secure against chosen-ciphertext attacks in the random oracle model. And the implementation and evaluation of the proposed scheme show that it is efficient and suitable for IoT devices.

A direct construction of continuous leakage-resilient (H)IBE scheme with CCA security from dual system encryption

Continuous leakage resilient semantically secure Identity-based Encryption (IBE) schemes created with dual system encryption technique were presented by Lewko et al. at TCC 2011 and Yuen et al. at Eurocrypt 2012, respectively. It has been a research challenge to achieve the security against chosen-ciphertext attacks (CCA). The previous attempts toward the CCA security rely on q-type assumptions, which are referred as non-static assumptions causing loose reduction in security proofs. In this paper, we provide a complete solution to the problem and show how to construct the continuous leakage-resilient IBE with weaker CCA security based on the dual system encryption technique, where the adversary is allowed to make continuous leakage queries. We are able to prove its security with static assumptions in the standard model. As a feature of our scheme, we allow leakage of multiple keys, i.e., leakage of the master secret key and the private key of user. Our scheme also enjoys better computational performance, since the round leakage parameter is independent of the plaintext space and has a constant size. Furthermore, our scheme can be easily extended to give the weaker CCA secure continuous leakage-resilient hierarchical identity-based encryption scheme with a short ciphertext length.

Achieving fuzzy matching data sharing for secure cloud-edge communication

In this paper, we propose a novel fuzzy matching data sharing scheme named FADS for cloud-edge communications. FADS allows users to specify their access policies, and enables receivers to obtain the data transmitted by the senders if and only if the two sides meet their defined certain policies simultaneously. Specifically, we first formalize the definition and security models of fuzzy matching data sharing in cloud-edge environments. Then, we construct a concrete instantiation by pairing-based cryptosystem and the privacy-preserving set intersection on attribute sets from both sides to construct a concurrent matching over the policies. If the matching succeeds, the data can be decrypted. Otherwise, nothing will be revealed. In addition, FADS allows users to dynamically specify the policy for each time, which is an urgent demand in practice. A thorough security analysis demonstrates that FADS is of provable security under indistinguishable chosen ciphertext attack (IND-CCA) in random oracle model against probabilistic polynomial-time (PPT) adversary, and the desirable security properties of privacy and authenticity are achieved. Extensive experiments provide evidence that FADS is with acceptable efficiency.

Efficient Storage and Encryption of 32-Slice CT Scan Images Using Phase Grating.

Medical images are treated as sensitive as it carries patients’ confidential information and hence must be protected from unauthorized access. So, a strong encryption mechanism is a primary criterion to transmit these images over the internet to protect them from intruders. In many existing algorithms, noise affection in the extracted images is high, hence not suitable for medical data encryption. Here, we present a new method using phase grating to multiplex as well as encrypting 32 cross-sectional CT scan images (slices) in a single canvas for optimization of storage space and improvement of security. The entire process is divided into a few steps. Before transmission, the main canvas is encrypted with the help of a random phase matrix. The main canvas is further encrypted by the transposition method to enhance security. After decryption, inverse Fourier transform is applied at the proper location of the decrypted canvas to extract the images from the spectra. Quality is measured with peak-signal-to-noise ratio and correlation coefficient methods. Here, it is greater than 38 and the correlation coefficient is close to 1 for all images, thereby indicating of good quality of extracted images. The effect of three common cyber-attacks (viz. known-plaintext attack, chosen-plaintext attack, and chosen-ciphertext attack) is also presented here. The correlation coefficient during cyber-attacks is found to be close to zero, which implies the robustness of the algorithm against cyber-attacks. Finally, a comparison with existing techniques shows the effectiveness of the proposed method.

Modified SHARK Cipher and Duffing Map-Based Cryptosystem

Recent years have seen a lot of interest in the study of chaotic structures and their accompanying cryptography frameworks. In this research, we came up with a new way to encrypt images that used the chaos and a modified block cipher named the SHARK cipher. The new algorithm looks at the creation of random sequences as a problem that needs to be solved in the best way possible, and then it uses the Duffing chaotic map to get even better random sequences. Chaos has been combined with a revised edition of the SHARK structure to make the algorithm design more robust with increased confusion and diffusion. The offered algorithm includes a complex encryption and decryption structure with minimal time consumption for secure data transmission. The proposed algorithm is verified with the encryption of some standard images of different sizes. Numerous analyses have been performed to see how well the algorithm works against a variety of assaults, and the outcomes show that the cryptosystem has a good level of robustness. The comparative results are also performed in this work, which guarantees the excellent performance of our cryptosystem. The system is also subjected to chosen-plaintext and chosen-ciphertext attacks which implies that it can resist many classical cryptographic attacks. Therefore, our cryptosystem is robust enough to use for image encryption.

Efficient Data Sharing With Privacy Preservation Over Lattices for Secure Cloud Storage

Data sharing is a basic data processing mechanism in the cloud storage. Data confidentiality and the receiver privacy are two important requirements of data-sharing systems. Because the data owner does not wish anyone who is not authorized to access the shared data and the authenticated data receiver also does not wish anyone else to know that he/she has accessed the shared data from the data owner. Broadcast encryption gives a possible solution to these requirements of data-sharing systems. This article constructs a data-sharing system over lattice by designing an efficient identity-based broadcast encryption (IBBE) scheme which achieves the data confidentiality and the identity privacy simultaneously. Besides the data owner, no one knows the identities of the authenticated data receivers in the proposed data-sharing system. Data confidentiality is achieved by the indistinguishability under the selective identity and the chosen ciphertext attacks (IND-sID-CCA) of the proposed IBBE scheme. It is proven in the random oracle model that the IND-sID-CCA security is based on the hardness of the learning with errors problem which can resist the quantum attacks. Inherited from the proposed IBBE scheme, the proposed data-sharing system also has several other characters which are suitable to the practical application. The most important feature is that all the public parameters size, private key size, and the ciphertext length are constant for any data receivers set in the proposed system. Hence, the proposed system adapts to the situation of large receiver group. Moreover, the proposed data-sharing system supports efficient member joining. When a new user asks to access the uploaded data, the existing receiver does not need to update his/her private key. The decryption cost of the existing receiver will remain unchanged when the outsourced data have been updated. Detailed performance analysis and a simulated experiment of the designed core algorithm are given by using Java program on a personal computer Intel Core i7-8700 K (3.7 GHz), 32 G RAM which verifies the design results in this article.

Certificateless Elliptic Curve Aggregate Signcryption Scheme

Driven by new situation of “Internet +,” Internet has achieved the integrated development with all walks of life. Among them, the fifth generation is a key technology to promote the deep integration of Internet-of-Things equipment, cloud computing, blockchain and other trades. Hence, it is necessary for IoTs to consider the cost and efficiency of authentication and confidentiality of the communication. For effectively solving the above problems, we devise certificateless elliptic curve aggregate signcryption (CL-ECASC) scheme for IoTs that can improve the authentication efficiency, realize data confidentiality, and avoid the problems of complex certificate management and key escrow. Under the hardness of discrete logarithm and computational DiffieHellman problems on elliptic curve, CL-ECASC is proved to has the IND-CCA2 security (indistinguishability under the adaptive chosen-ciphertext attacks) and UF-CMA security (existentially unforgeable under the adaptive chosen-message attacks). CL-ECASC has relatively faster computation efficiency and lower communication cost, and so it is suitable for secure transmission of the information in the previously mentioned environments.

Group public key encryption supporting equality test without bilinear pairings

In cloud computing scenarios, it is a common approach to encrypt the data before uploading in order to maintain the privacy. Public key encryption with equality test (PKEET) provides a generic solution to equality comparisons on encrypted data. Considering the practical requirements of PKEET in group user scenarios, Ling et al. presented a group public key encryption scheme with equality test (G-PKEET) by utilizing the computationally expensive bilinear pairing operations. In this paper, we propose an efficient and verifiable group public key encryption with equality test construction without bilinear pairings (GPKEET/BP). Our proposal is developed from a basic observation that two points determine a straight line, and is proven to be indistinguishable against the chosen-ciphertext attacks (IND-CCA) in the random oracle model under the computational Diffie-Hellman (CDH) assumption. Theoretical analysis shows that our construction only involves several modular exponentiations in the encryption, decryption and test algorithms. The theoretical results are well supported by experimental simulations, which show that the test algorithm of GPKEET/BP performs about 92% faster than that of Ling et al.’s scheme. So our GPKEET/BP scheme turns out to be better suited for group ciphertext equality test situations.

Cloud Storage Data Access Control Scheme Based on Blockchain and Attribute-Based Encryption

Cloud storage is a popular model of the application in various fields, and the security of storage data and access permission have been widely considered. Attribute-based encryption (ABE) provides fine-grained user access control and ensures data confidentiality. However, current ABE access control schemes rely on trusted cloud servers and provide a low level of security. To solve these problems of traditional encryption schemes, we propose a blockchain-based and ABE cloud storage data access control scheme. In this article, blockchain and smart contract technology are the core elements to ensure data integrity and build a decentralized verification method for outsourcing results. This application can minimize the reliance on servers in the cloud environment. Based on the ciphertext-policy ABE algorithm, the proposed scheme supports a hidden access policy to avoid the risk of privacy leakage. In addition, we adopt outsourcing technology and predetected decryption algorithms to reduce the computational overhead of local and outsourced servers. Security analysis and performance evaluation show that our proposed scheme has high computational efficiency and satisfies the condition of indistinguishability under the chosen-ciphertext attacks.

Identity-Based Encryption With Continuous Leakage-Resilient CCA Security From Static Complexity Assumption

Abstract Although a large number of provably secure cryptographic primitives have been proposed in the literature, many of these schemes might be broken in practice because of various leakage attacks. Therefore, the leakage resilience should be considered in designing these primitives. However, in identity-based cryptography, most of the existing leakage-resilient identity-based encryption (IBE) schemes suffer some limitations: they either resist the leakage attacks in the selective identity security model or achieve the chosen-ciphertext attack (CCA) security based on a non-static assumption. In this paper, an IBE scheme with adaptive leakage-resilient CCA security is proposed, and its security is rigorously proved in the random oracle model under a classic static complexity assumption, e.g. decisional bilinear Diffie–Hellman assumption. In our construction, all elements of ciphertext are randomly distributed in the adversary’s view. Hence, the adversary cannot obtain any useful information of the user’s private key from the given ciphertexts. Moreover, a unique property of our construction is that the leakage parameter is independent of the plaintext space, which contributes a better leakage rate.

Proxy Re-Encryption Scheme for Decentralized Storage Networks

Storage is a promising application for permission-less blockchains. Before blockchain, cloud storage was hosted by a trusted service provider. The centralized system controls the permission of the data access. In web3, users own their data. Data must be encrypted in a permission-less decentralized storage network, and the permission control should be pure cryptographic. Proxy re-encryption (PRE) is ideal for cryptographic access control, which allows a proxy to transfer Alice’s ciphertext to Bob with Alice’s authorization. The encrypted data are stored in several copies for redundancy in a permission-less decentralized storage network. The redundancy suffers from the outsourcing attack. The malicious resource provider may fetch the content from others and respond to the verifiers. This harms data integrity security. Thus, proof-of-replication (PoRep) must be applied to convince the user that the storage provider is using dedicated storage. PoRep is an expensive operation that encodes the original content into a replication. Existing PRE schemes cannot satisfy PoRep, as the cryptographic permission granting generates an extra ciphertext. A new ciphertext would result in several expensive replication operations. We searched most of the PRE schemes for the combination of the cryptographic methods to avoid transforming the ciphertext. Therefore, we propose a new PRE scheme. The proposed scheme does not require the proxy to transfer the ciphertext into a new one. It reduces the computation and operation time when allowing a new user to access a file. Furthermore, the PRE scheme is CCA (chosen-ciphertext attack) security and only needs one key pair.

ECCHSC: Computationally and Bandwidth Efficient ECC-Based Hybrid Signcryption Protocol for Secure Heterogeneous Vehicle-to-Infrastructure Communications

Vehicular ad hoc networks (VANETs), an application of the Internet of Things (IoT) providing a better intelligent transportation system (ITS), has received substantial attention from both industry and academia. Heterogeneous vehicular communications in VANETs occur when both vehicles and the infrastructure use different cryptographic technologies to exchange safety messages. However, the safety messages between vehicles and the infrastructure are communicated wirelessly; therefore, security issues are a serious concern in this domain. The existing schemes secure the transmission of safety messages with respect to confidentiality, authentication, and nonrepudiation. However, they are inappropriate with respect to efficiency. They cause computational overhead on the receiver and bandwidth overhead in the communications. To cope with this, we propose an elliptic curve cryptosystem-based hybrid signcryption (ECCHSC) protocol that satisfies the security requirements (i.e., message confidentiality, message’s source authentication, message integrity, nonrepudiation, and identity–anonymity) for heterogeneous vehicle-to-infrastructure (V2I) communications in a single logical step. This protocol allows secure transmission of a safety message from a vehicle using identity-based cryptography (IDC) to a roadside unit (RSU) using public-key infrastructure (PKI). In addition, the ECCHSC protocol enables the RSU to receive multiple ciphertexts, aggregate them, and de-signcrypt them simultaneously through the batch de-signcryption method, which further improves the performance. The ECCHSC protocol has indistinguishability against adaptive chosen ciphertext attacks (IND-CCA2) and existential unforgeability against adaptive chosen message attacks (EUF-CMAs) in the random oracle model (ROM). The performance analysis of our protocol demonstrates a significant reduction in computational overhead and in communication/storage overhead as compared to the state-of-the-art schemes.

Security of COFB against Chosen Ciphertext Attacks

COFB is a lightweight Authenticated Encryption with Associated Data (AEAD) mode based on block ciphers. It was proposed in CHES 2017 and is the basis for GIFT-COFB, a finalist in the NIST lightweight standardization project. It comes with provable security results that guarantee its security up to the birthday bound in the nonce-respecting model. However, the designers offer multiple versions of the analysis with different details and the implications of attacks against the scheme are not discussed deeply. In this article, we look at a group of possible forgery and privacy attacks against COFB. We show that the security for both forgery and privacy is bounded by the number of forgery attempts. We show the existence of forgery and privacy attacks with success probability qd/2n/2, given qd forgery attempts. In particular, we show an attack with 2n/2 attempts using only a single known-plaintext encryption query against COFB. While these attacks do not contradict the claims made by the designers of GIFT-COFB, they show its limitations in terms of the number of forgery attempts. They also show that, while COFB generates a 128-bit tag, it behaves in a very similar manner to an AEAD scheme with 64-bit tag. As a result of independent interest, our analysis provides a contradiction to the main theorem of Journal of Cryptology volume 33, pages 703–741 (2020), which includes an improved security proof of COFB compared to the CHES 2017 version. Finally, we discuss the term nqd/2n/2 that appears in the security proof of GIFT-COFB and CHES 2017, showing why there is a security gap between the provable results and the attacks. We emphasize that the results in this article do not threaten the security of GIFT-COFB in the scope of the NIST lightweight cryptography requirements or the claims made by the designers in the specification document of the design.

Modified Playfair cryptosystem for improved data security

Playfair is the earliest known classical block cipher which is capable of taking two characters as a unit in the process of encryption and decryption. However, the cipher is suffering from vulnerability to many cryptanalysis attacks due to a lack of confusion and diffusion properties, an inability to handle numbers and special characters in the process of encryption and decryption, and a host of other deficiencies. Although several modifications and improvements had been done by different researchers, the emphasis has been on the modification of the key matrix to accommodate more characters to increase the keyspace. No attention has been given to increment in the size of the block that the Playfair cipher can handle at a time. In this paper, a modified Playfair (MPF) cryptosystem that is capable of handling different block sizes with high diffusion and confusion properties is developed. cryptanalysis of the developed cryptosystem was carried out and the results show that the MPF cryptosystem is resistant to Known plaintext attack, chosen-plaintext attack, chosen ciphertext attack, frequency analysis attack, autocorrelation attack, differential cryptanalysis attacks, entropy attacks, brute force attack, and can handle variable block sizes.