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The evolution of the cloud computing furnishes a better way for the data storage. ABE with delegation is accustomed for accessing the data and keep it confidential. But this scheme faces some limitations like the cloud servers can replace the cipher text with some malignant intent. They may also cheat the eligible users as unauthorized ones. The cloud servers even face external threats like the security attacks. So, to protect against the security attacks and to preserve the data integrity in the cloud, a hybrid encryption with VD scheme is proposed by Xu et al. Even this scheme faces the challenges like having larger keys, more computational time and vulnerability to man-in-the-middle attacks. A secure Hybrid Encryption using ECC in clouds is proposed to overcome these problems. The application of Elliptic Curve Cryptography and its algorithms in the proposed work provides a greater security because of the Elliptic Curve Discrete Logarithm Problem. The proposed work ensures greater security with the aid of a smaller key size. It also ensures less computational time, less memory and communication bandwidth. [ABSTRACT FROM AUTHOR]

In view of the problems of inefficient data encryption, non-support of malicious user revocation and data integrity checking in current smart grid data sharing schemes, this paper proposes a blockchain-based multi-authority revocable data sharing scheme in the smart grid. Using online/offline encryption technology with hybrid encryption technology enhances the encryption performance for the data owner. The use of user binary tree technology enables the traceability and revocability of malicious users. The introduction of multiple attribute authorization authorities eliminates the threat of collusive attacks that exist in traditional data-sharing schemes. In addition, the semi-honest problem of third-party servers is solved by uploading data verification credentials to the blockchain. The security analysis results show that the scheme can resist selective plaintext attacks and collusion attacks. The performance analysis results show that the proposed scheme has lower computational overhead and better functionality than similar schemes, which is suitable for secure data sharing in smart grids.

The circular security of public key encryptions has been drawn great attentions in recent years. The relationship of notions between circular securities and standard ones such as chosen plaintext security (CPA-security) and chosen ciphertext security (CCA-security) deserve to be clarified. For any integer n > 0 and n ≠ 2, whether the notions of n-circular securities can be implied by that of their standard correspondences, such as CPA or CCA security in public key setting, has largely remained open. Koppula, Ramchen, and Waters in TCC'15 recently made a separation in CPA case by proposing a CPA secure scheme that is not n-circular secure based on the recent candidate constructions of indistinguishable obfuscation. In this work, we consider the CCA case. In particular, inspired by the indistinguishable-obfuscation-based construction of Koppula et al., we obtain the following results: We make a separation between the n-circular CCA security and CCA security for anyn>0. Specifically, we propose a hybrid encryption scheme that achieves the CCA security but fails even in the n-circular CPA security. Hence, that makes a separation between the CCA security and the n-circular CCA security (and even the n-circular CPA security)., By revising the previous construction, we also present a CCA secure (hybrid encryption) scheme, which allows an adversary to recover all secret keys when obtaining an encrypted key cycle. Hence, that implies that: if a key cycle arises in a system, then a passive adversary might be able to recover all secret keys even if CCA-secure encryptions are used., The results in this work, together with that of Koppula et al., confirm that notions of circular securities are stronger than their standard correspondences. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Data security is of utmost importance in today's world. Especially when the data is travelling through an insecure communication network. There are symmetric key encryption techniques which use only one key for both encryption and decryption of the data. They are simple in design but can be easily cracked using brute force attacks. The entire security of such a cipher could be compromised if the attacker anyhow gets access to the keys. On the other hand, there are asymmetric key based algorithms which use a pair of keys, one for encryption, and the other for decryption, whose security is higher as compared to the symmetric ones but lack in time efficiency. It is also difficult to manage such a huge base of key-pairs efficiently and safely. This paper mainly focusses on the implementation of a system capable of encryption and decryption of multimedia data (Text, Images, Videos, Audio etc.) using a hybrid model based on the amalgamation of symmetric encryption techniques such as AES and asymmetric techniques such as ECC. ECC is based on the toughness of the discrete logarithm problem (DLP), whose public key is short, network bandwidth is little and ability to resist to attack is strong which makes it really difficult to guess the keys. Even if the attacker gets access to any of the keys, he or she won’t be in a position to decipher it in a relatively finite amount of man-years. [ABSTRACT FROM AUTHOR]

In the cloud, for achieving access control and keeping data confidential, the data owners could adopt attribute-based encryption to encrypt the stored data. Users with limited computing power are however more likely to delegate the mask of the decryption task to the cloud servers to reduce the computing cost. As a result, attribute-based encryption with delegation emerges. Still, there are caveats and questions remaining in the previous relevant works. For instance, during the delegation, the cloud servers could tamper or replace the delegated ciphertext and respond a forged computing result with malicious intent. They may also cheat the eligible users by responding them that they are ineligible for the purpose of cost saving. Furthermore, during the encryption, the access policies may not be flexible enough as well. Since policy for general circuits enables to achieve the strongest form of access control, a construction for realizing circuit ciphertext-policy attribute-based hybrid encryption with verifiable delegation has been considered in our work. In such a system, combined with verifiable computation and encrypt-then-mac mechanism, the data confidentiality, the fine-grained access control and the correctness of the delegated computing results are well guaranteed at the same time. Besides, our scheme achieves security against chosen-plaintext attacks under the $k$ -multilinear Decisional Diffie-Hellman assumption. Moreover, an extensive simulation campaign confirms the feasibility and efficiency of the proposed solution. [ABSTRACT FROM AUTHOR]

Detectable Chosen Ciphertext (DCCA) security is a useful notion to achieve CCA security for public-key encryptions (PKE). An "inner-outer" structure can transform a DCCA-secure PKE into a CCA-secure one. In the structure, the "inner" layer encrypts both the message and the two embedded randomness, so a key encapsulated mechanism (KEM) + data encapsulation mechanism (DEM) hybrid paradigm helps to gain time efficiency. Nevertheless, the long "inner" ciphertext still makes the "outer" encryption less efficient. We show that the structure can be applied solely on the KEM part, and even the embedded randomness can be encrypted outside the structure by introducing a CCA-secure DEM. These reduce the length of the "inner" ciphertext, thus avoiding some redundant re-encryptions in the "outer" layer and offload as much of the work as possible from KEMs to faster DEMs. Combined with a recent improvement made on the "outer" layer, we can gain better time and space efficiency. Additionally, we prove that when a DCCA-secure KEM satisfies the so-called "translatability", a proper related-key secure DEM helps to achieve CCA security directly by applying the hybrid paradigm without any use of the less efficient "inner-outer" structure. [ABSTRACT FROM AUTHOR]

A non-interactive zero-knowledge (NIZK) proof can be used to demonstrate the truth of a statement without revealing anything else. It has been shown under standard cryptographic assumptions that NIZK proofs of membership exist for all languages in NP. While there is evidence that such proofs cannot be much shorter than the corresponding membership witnesses, all known NIZK proofs for NP languages are considerably longer than the witnesses. Soon after Gentry's construction of fully homomorphic encryption, several groups independently contemplated the use of hybrid encryption to optimize the size of NIZK proofs and discussed this idea within the cryptographic community. This article formally explores this idea of using fully homomorphic hybrid encryption to optimize NIZK proofs and other related cryptographic primitives. We investigate the question of minimizing the communication overhead of NIZK proofs for NP and show that if fully homomorphic encryption exists then it is possible to get proofs that are roughly of the same size as the witnesses. Our technique consists in constructing a fully homomorphic hybrid encryption scheme with ciphertext size $$|m|+{\mathrm {poly}}(k)$$ , where $$m$$ is the plaintext and $$k$$ is the security parameter. Encrypting the witness for an NP-statement allows us to evaluate the NP-relation in a communication-efficient manner. We apply this technique to both standard non-interactive zero-knowledge proofs and to universally composable non-interactive zero-knowledge proofs. The technique can also be applied outside the realm of non-interactive zero-knowledge proofs, for instance to get witness-size interactive zero-knowledge proofs in the plain model without any setup or to minimize the communication in secure computation protocols. [ABSTRACT FROM AUTHOR]

Traditional video conference systems depend largely on computational complexity to ensure system security, but with the development of high-performance computers, the existing encryption system will be seriously threatened. To solve this problem, a hybrid encryption scheme for quantum secure video conferencing combined with blockchain is proposed in this study. In the system solution architecture, first, the quantum key distribution network is embedded in the classic network; then, the "classical + quantum" hybrid encryption scheme is designed according to the secret level required for the video conference content. Besides, the real-time monitoring module of the quantum key distribution network is designed to ensure that users can check the running state of the network at any time. Meeting minutes can be shared by combining with blockchain. In order to quickly query meeting minutes, a cache-efficient query method based on B+ tree is proposed. The experimental results show that compared with the traditional video conference system, the quantum secure video conference system sufficiently integrates the technical advantages of the quantum key distribution to resist the security threats such as channel eavesdropping and high-performance computational attacks while ensuring the stable operation of the classic system, thus providing a video conference system with a higher security level. Meanwhile, the query time cost of blockchain with different lengths is tested, and the query efficiency of the proposed method is 3.15-times higher than the original query efficiency of blockchain. [ABSTRACT FROM AUTHOR]

Key-dependent message (KDM) security should be considered in the design of security protocols, especially for complicated ones, where the messages related to the secret key might be encrypted. In this paper, we present a new method of constructing a KDM secure asymmetric encryption scheme with the notation of hybrid encryption in the standard model; although the notation of hybrid encryption was thought as no help to get rid of dependencies between messages and the secret key. Our result can also be seen as a partial instantiation for a previously well-known KDM secure asymmetric encryption scheme based on random oracle. As we know, this has never been carried out before. And our result indicates a new cryptographic application for the primitive of lossy trapdoor function. Throughout the paper, our main idea is to archive KDM security by making use of both leakage-resilience and auxiliary-input security properties. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We introduce an efficient signcryption scheme for hybrid authenticated encryption that is provably secure in the standard model under a strong multiuser insider setting. Our new signcryption scheme is built on the basis of a variant of Boneh-Boyen short signature, which works under bilinear groups. The new construction idea is to reuse the signature value to derive the encryption key. This could dramatically save not only the computational cost but also the communication bandwidth. The session key security of the proposed scheme is reduced to a hard problem that is a variant of bilinear decisional Diffie-Hellman problem. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The Internet of Things (IoT) in communication networks has gained major interest in recent decades. Accordingly, secure authentication of such individuals results in a major challenge due to the weakness in the authentication process. Hence, an effective Hybrid and Adaptive Cryptographic (HAC)-based secure authentication framework is designed in this research to perform an authentication process in IoT. The proposed approach uses cryptographic operations, like exclusive-or (Ex-or) operation, a hashing function, and hybrid encryption to accomplish the authentication process. However, the hybrid encryption function is carried out in two different ways: one depends on Advanced Encryption Standard (AES) as well as Elliptic Curve Cryptography (ECC), while other is based on Rivest Shamir Adleman (RSA) and AES. With a hybrid encryption function, security flaws can be effectively dealt through the cryptographic system. Moreover, the proposed approach provides high robustness with low complexity. The proposed HAC-based secure authentication approach obtained a minimum communication cost of 0.017sec, less computation time of 0.060sec, and minimum memory usage of 2.502MB, respectively. [ABSTRACT FROM AUTHOR]

ABSTRACT Replayable chosen-ciphertext attack (RCCA) security is a weaker notion than chosen-ciphertext attack (CCA) security and has been proven to be sufficient for several cryptographic tasks. However, it is open to construct RCCA-secure schemes more efficient than CCA-secure ones. This paper adapts RCCA security to the most popular hybrid paradigms, KEM+DEM and Tag-KEM/DEM. For KEM+DEM paradigm, we show RCCA security is consistent with the CCA case, just as desired. But for Tag-KEM/DEM paradigm, we find some different status. Natural RCCA-secure Tag-KEM schemes can be easily constructed, which are more efficient than all existing CCA-secure ones. But unfortunately, passive security of DEM is not sufficient to obtain RCCA hybrid encryptions. In spite of this and for completeness, we show RCCA-secure DEMs are still sufficient. On the other hand, for passive secure DEMs, we prove that a stronger notion of RCCA security for Tag-KEM, named as tRCCA security, suffices for RCCA-secure hybrid encryptions. This somewhat suggests that a benign RCCA security for tag-based schemes should be tRCCA security. Finally, to show RCCA-secure KEM is sufficient for achieving CCA-secure hybrid encryptions, we introduce a new hybrid paradigm, named as KEM/Tag-DEM, where the ciphertext of KEM is used as a tag for Tag-DEM scheme rather than reversely in Tag-KEM/DEM, so that the security of KEM can be weakened to RCCA one. KEM/Tag-DEM shows the diversity of hybrid encryptions and has additional practical values. We also show Tag-DEMs can be constructed as efficiently as DEMs. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

To increase the tax collection of mineral resources and enhance the management of resource exploitation, computerized mineral management information systems (MMIS) are developed and applied to the government management system. The MMIS are run at checking portals that inspect trucks transporting minerals. Only the trucks with the special permit (also called ticket) can pass through the checking portal after the ticket is correctly authenticated by the MMIS. Due to the huge economic benefits of the special tickets, the tickets are frequently fabricated. Because tickets are exoteric and current, the security of them becomes an urgent problem. In this paper, a novel security mechanism is proposed for the mineral management information system, in which the hash function, AES (Advanced Encryption Standard) encryption algorithm and ECC (Elliptic Curve Cryptography) encryption algorithm are hybrid to encode and encrypt the data involved with the ticket according to different sensitivity levels. Data are dynamically and separately stored into the disk storage or RFID (Radio Frequency Identification) tags storage. Identity authentication of the ticket is achieved by data in the two-dimensional bar code printed on the ticket, the RFID tag that is installed on the truck with the ticket, and the disk storage of MMIS database. MMIS equipped with the presented ticket encryption mechanism is secure and results in great economic and society interests. [ABSTRACT FROM AUTHOR]

It is possible that an adversary may attack to conventional key encapsulation mechanism (KEM) and data encapsulation mechanism (DEM) structure, if any weakness exists in these algorithms. In order to prevent such kind of attacks and to make the KEM-DEM structure secure in a very strong sense, we propose a scramble algorithm in which KEM and DEM are combined and permuted, then encrypted with symmetric key driving into one block. In addition, for a long term communication between two nodes, we propose a new scheme Combined KEM-DEM which provides message integrity and sender's identity control via an integrated session key. In this method, each message is encrypted with different symmetric key and whole communication traffic is controlled. Simulations made using RSA with different key lengths (256, 512, and 1024 bits) show that by employing the Combined KEM-DEM scheme, computation times of KEM for the encryption and decryption are reduced by 40% as compared to Tag-KEM/DEM [2] and Fujisaki-Okamoto's KEM-DEM [3] schemes. [ABSTRACT FROM AUTHOR]

This paper presents a novel framework for the generic construction of hybrid encryption schemes which produces more efficient schemes than the ones known before. A previous framework introduced by Shoup combines a key encapsulation mechanism (KEM) and a data encryption mechanism (DEM). While it is sufficient to require both components to be secure against chosen ciphertext attacks (CCA-secure), Kurosawa and Desmedt showed a particular example of KEM that is not CCA-secure but can be securely combined with a specific type of CCA-secure DEM to obtain a more efficient, CCA-secure hybrid encryption scheme. There are also many other efficient hybrid encryption schemes in the literature that do not fit into Shoup’s framework. These facts serve as motivation to seek another framework. The framework we propose yields more efficient hybrid scheme, and in addition provides insightful explanation about existing schemes that do not fit into the previous framework. Moreover, it allows immediate conversion from a class of threshold public-key encryption to a threshold hybrid one without considerable overhead, which may not be possible in the previous approach. [ABSTRACT FROM AUTHOR]

This paper presents the experimental results that were obtained by implementing the payload of a cryptovirus on the Microsoft Windows platform. The attack is based entirely on the Microsoft Cryptographic API and the needed API calls are covered in detail. More specifically, it is shown that by using eight types of API calls and 72 lines of C code, the payload can hybrid encrypt sensitive data and hold it hostage. Benchmarks are also given. A novel countermeasure against cryptoviral extortion attacks is shown that forces the API caller to demonstrate that an authorized party can recover the asymmetrically encrypted data. [ABSTRACT FROM AUTHOR]

In traditional database security research, the database is usually assumed to be reliable. Under this assumption, the goal is to achieve security against external attacks, for instance from hackers and possibly also against users trying to obtain information beyond their privileges, for instance by some type of statistical inference. Therefore the database cannot necessarily be assumed to be fully trusted. Data in a database is very important. We must assure their security completely. It points out that it is difficult to ensure the security of the system by using a single encryption technology. This paper introduces the basic technologies of symmetrical encryption, asymmetrical encryption and then the hybrid encryption thoughts of combining the both are promoted. By using this method, the security of databases is enhanced. [ABSTRACT FROM AUTHOR]