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Federated learning-based automotive navigation has recently received considerable attention, as it can potentially address the issue of weak global positioning system (GPS) signals under severe blockages, such as in downtowns and tunnels. Specifically, the data-driven navigation framework combines the position estimation offered by the high-sampling inertial measurement units and the position calibration provided by the low-sampling GPS signals. Despite its promise, the privacy preservation and flexibility of the participating users in the federated learning process are still problematic. To address these challenges, in this article, we propose an efficient, flexible, and privacy-preserving model aggregation scheme under a federated learning-based navigation framework named FedLoc . Specifically, our proposed scheme efficiently protects the locally trained model updates, flexibly supports the fluctuation of participants, and is robust against unregistered malicious users by exploiting a homomorphic threshold cryptosystem, together with the bounded Laplace mechanism and the skip list. We perform a detailed security analysis to demonstrate the security properties in terms of privacy preservation and dishonest user detection. In addition, we evaluate and compare the computational efficiency with two traditional schemes, and the simulation results show that our scheme greatly improves the computational efficiency during participant fluctuation. To validate the effectiveness of our scheme, we also show that only part of the model update is excluded from aggregation in the case of a dishonest user.

Big data, the upcoming technology in the field of computing, refers to a large complex dataset. It deals with large complex datasets and yields great valued information when analysed properly. Data Security has become the greatest challenge in the minds of cyber experts and researchers in this scenario. Apache Hadoop frameworks that let distributed processing of these large datasets rely on Kerberos Authentication for mutual authentication and verification. The protocol comes with inherent challenges like Single point of failure, Dictionary Attacks, Replay Attacks, and Time Synchronization problems. This paper puts forward a one-off approach based on recent technologies like Blockchain Networks, Digital Signatures, and Elliptic ElGamal and Threshold Cryptosystem. The proposed scheme aims to mainly deal with the Single Point of Failure problem. Riverbed Modeller (AE) simulation is performed to do the comparative study of the proposed scheme with existing systems that use traditional encryption standards like RSA cryptosystems. Analysis of the simulation results proves that the proposed scheme is more efficient in terms of time and memory without compromising the level of security offered. The response time, network delay and traffic rates of the proposed system are compared with the existing RSA based system and the results strengthen the claims of this work. Lastly, the results from comparative analysis of security features and computational time cost indicate that the proposed method heightens the security level offered for big data systems with a nominal effect on performance.

We propose the first hierarchical and dynamic threshold Paillier cryptosystem without trusted dealer and prove its security in the malicious adversary model. The new cryptosystem is fully distributed, i. e., public and private key generation is performed without a trusted dealer. The private key is shared with a hierarchical and dynamic secret sharing scheme over the integers. In such a scheme not only the amount of shareholders, but also their levels in the hierarchy decide whether or not they can reconstruct the secret and new shareholders can be added or removed without reconstruction of the secret.

In the early years after the invention of public key cryptography by Diffie and Hellman in 1976, the design and evaluation of public key cryptosystems has been done merely in ad-hoc manner based on trial and error. The public key cryptosystem said to be secure as long as there is no successful cryptanalytic attack on it. But due to various successful attacks on the cryptosystems after development, the cryptographic community understood that this ad-hoc approach might not be good enough. The paradigm of provable security is an attempt to get rid of ad hoc design. The goals of provable security are to define appropriate models of security on the one hand, and to develop cryptographic designs that can be proven to be secure within the defined models on the other. There are two general approaches for structuring the security proof. One is reductionist approach and other is game-based approach. In these approaches, the security proofs reduce a well known problem (such as discrete logarithm, RSA) to an attack against a proposed cryptosystem. With this approach, the security of public key cryptosystem can be proved formally under the various models viz. random oracle model, generic group model and standard model. In this chapter, we will briefly explain these approaches along with the security proofs of well known public key cryptosystems under the appropriate model.

In this study, we consider an equivalence test on rational numbers in a scenario with K + 2 distributed parties, Alice, Bob, P 1 , P 2 , … , P K , where Alice has a private rational number xa, Bob has a private rational number xb, and party Pi has a secret si, where i ∈ { 1 , 2 , … , K } , K ≥ 2. The parties want to cooperatively detect whether x a = x b without revealing any information about their secrets. This problem has many applications in online collaboration, such as e-voting, which requires public verifiability. First, we develop a provably secure threshold cryptosystem for rational numbers. Next, based on the proposed threshold scheme, we construct a distributed plaintext equivalence test protocol in an honest majority environment. We prove that the proposed protocol is secure and robust in the standard (ideal/real) model.

Information security in cloud computing technology is actively investigated by the world scientific community. They uses the internet and the central remote servers to provide and maintain data as well as applications. This users' data files can be accessed and manipulated by any other users. So the problem of secure data storage and computation is actual. The modern studies in this field shows that the indicated problem is much more complex than any of the other information security problems, which are solved by well-known cryptographic methods. So, for example M. van Dijk and A. Juels in the paper "On the impossibility of cryptography alone for privacy-preserving cloud computing" described a mathematical model of the organization of cloud computing and proved that in the case of two users information protection is impossible. This result refutes the well-established point of view that the recently proposed by C. Gentry construction for fully homomorphic encryption solves at least theoretically, all the problems of information security in cloud computing. We offer an alternative model of cloud computing, in which the specified negative result does not holds. It differs from the above in the point that each subject interested in privacy, creates his own crypto server. From the point of view of users these cryptoservers are the part of the cloud. The methods of information protection, using threshold cryptosystem in this new model are investigated.

The centralized exchange is one of the hottest DeFi applications based on blockchain transaction systems. However, depositing user assets to the exchanges brings the security risks of assets misappropriation. Threshold cryptosystem can effectively solve the drawbacks of centralized hosting by assigning the assets authorization to multiple trustees, but the collusion attack generated by malicious trustees is still unavoidable. In this paper, we propose a new dynamic threshold ECDSA signature scheme which is compatible with current blockchain transaction system. It realizes distributed custody of assets in exchanges, and further achieves a dynamic mechanism allowing user join and drop out to resist collusion attacks. Specifically, we formalize the definition of this system architecture and give its construction based on basic cryptography modules such as ECDSA signature, distributed key generation, and distributed computation. Analysis and experiment results show that our scheme holds protocol security and is more efficient than other threshold ECDSA signature schemes when threshold is less than 200, which makes it applicable to the assets custody scenarios of exchanges.

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.

Esmaeili and Gulliver recently proposed a secret key cryptosystem based on error-correcting codes in which a codeword modified by random insertions, deletions, and errors is used as a ciphertext. The secret keys used in this cryptosystem consist of random numbers generated by synchronized random number generators that are implemented using two distinct linear feedback shift registers (LFSRs) in each encryptor and decryptor, respectively. In this letter, we propose a ciphertext-only attack to break the Esmaeili-Gulliver cryptosystem based on LFSRs. The proposed attack requires $O(n)$ consecutive ciphertexts, where $n$ is the number of shift registers in the LFSR, which is the secret key size. The proposed attack consists of two steps, and the time complexity of the first step is linear in the secret key size while the second step is a polynomial-time algorithm.

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

Elliptic curve cryptography is used as a public-key cryptosystem for encryption and decryption in such a way that if one has to encrypt a message, then they attempt to map the message to some distinct point on the elliptic curve by modifying the message using a mapping algorithm. Although the arithmetic involved in elliptic curve cryptography is computationally less complex than other cryptographic algorithms, but conversion of simple messages to points on the elliptic curve has always been challenging. In this paper, we discuss the different schemes of message mapping in elliptic curve cryptosystem, the flaws of each method, and how vulnerable they are to cryptanalysis. We also derive the guidelines of a good message mapping scheme in elliptic curve cryptosystem. In the later part of this paper, we will discuss about a new mapping scheme that is resistible to frequency analysis and other forms of cryptanalysis. Copyright © 2016 John Wiley & Sons, Ltd.

A cryptosystem is a cryptographic scheme that allows a sender to encrypt and send a confidential message or document by using public key, while the receiver can decrypt the encrypted message into its original form by using secret key. Most of the existing cryptosystems are constructed based on single hard number theoretical problems. Furthermore, the concept of group-oriented cryptosystem, known as threshold cryptosystem gives an important role in developing a cryptosystem. In this research, a threshold cryptosystem based on two hard number theoretical problems is presented. The strength of this new threshold cryptosystem is the difficulty to solve both factoring and discrete logarithm problems simultaneously. The security analysis of the scheme shows that it is secure against common security attacks.

In this paper, we propose a secure blockchain-based electronic voting (e-voting) system with distributed authorities. Specifically, we employ threshold blind signature to distribute trust for registration; and threshold ElGamal decryption to distribute trust in ballots tallying. Combining these techniques with decentralized blockchain technology, our system can achieve verifiability, eligibility, fairness and anonymity with reduced trust. We also analyze the efficiency of our system by implementing the proposed e-voting system on a typical laptop for performance evaluation. Our system is efficient enough to be employed in practice based on the experiment results.

Publicly Verifiable Randomness has many useful and interesting applications in e-voting, distributed cryptography, secure multiparty computation, lotteries, sports seeding and many more. While the output of a Publicly Verifiable Randomness is provably unpredictable for a strong adversary, it is expected that its closeness to a uniform distribution is verifiable for any party. The inherent randomness in public blockchains such as Bitcoin has been the topic of several research papers and been used in lotteries and other multi-party protocols. However, recently it has been argued that an adversary can have a significant impact on the probability distribution of the output with much lower financial cost. Here, in this paper, we propose a new scheme based on the properties of Verifiable Secret Sharing protocols and Threshold Cryptosystems, that uses semi-trusted third parties to improve the security of Verifiable Public Randomness from any public blockchain. We argue that a successful attack against our scheme to impose a bias on a single bit of the output randomness requires not only a significant financial cost but also a corruption of more than k out of n trusted delegates.

Signcryption is a public key cryptosystem that achieves the functions of digital signature and public key encryption simultaneously. It significantly reduces the cost of traditional signature-then-encryption approach. Although a large body of signcryption schemes have been proposed, few works have been done on attribute-based signcryption (ABSC), which simultaneously achieves the functionalities of attribute-based encryption and attribute-based signature, two important cryptographic primitives proposed to enforce fine-grained access control and user authentication in cloud computing applications. In this paper, we present a threshold ABSC scheme. The scheme is proven secure under the well-established Decisional Bilinear Diffie–Hellman and the standard Computational Diffie–Hellman assumptions in the standard model. Compared with the state of the ABSC art, our scheme has comparable efficiency without relying on any random oracle. Furthermore, we construct an authenticated key agreement protocol based on this threshold attribute-based signcryption from the point of improving the security of cloud computing. Copyright © 2016 John Wiley & Sons, Ltd.

In this letter, a new code based cryptosystem with a public code is introduced. This cryptosystem is based on randomly flipping, deleting, and inserting bits into a codeword corresponding to a plaintext. The construction of a secure channel coding scheme using the proposed cryptosystem is presented. The key size and security of this scheme are analyzed. Not having the code as part of the key results in a key size comparable to many well-known symmetric key cryptosystems. It is shown that the best approach for an adversary to obtain the key has a very low success rate, which indicates that the cryptosystem provides excellent security.

We study a formal model of cloud computing systems with auxiliary cryptoservers. Assuming an existence of a secure threshold somewhat homomorphic public key cryptosystem we show how to build a cloud computing system secure in this model.

For fine-grained data access control in cloud computing, for the first time, we introduce a new concept called restricted proxy re-encryption with keyword search, which combines the function of proxy re-encryption with keyword search and that of threshold cryptosystem. To demonstrate this concept, we present the formal syntax for restricted proxy re-encryption with keyword search, the security model, and a concrete construction. In our scheme, we take advantage of the techniques of threshold cryptosystem to restrict the capacity of the proxy cloud server, and in the meantime, we let the proxy cloud server can only re-encrypt the data containing a specified keyword, which matches the trapdoor from delegatee to provide an accurate access control for users. While in this process, the proxy cloud server learns nothing about the contents of data and keyword. Our scheme is proved to be semantically secure under the modified bilinear Diffie-Hellman assumption and the q-decisional bilinear Diffie-Hellman inversion assumption in the random oracle model. Finally, we apply the techniques in our scheme to some practical problems. Copyright © 2016 John Wiley & Sons, Ltd.

The concept of “threshold cryptosystem” is fresh and rare in the field of optical information security. Based on a phase retrieval algorithm, we propose a novel threshold scheme with optical realization. In this method, a secret image is encoded into three phase-only masks (POMs), of which any two could recover the secret image but any single one could not. Besides, every POM is designed to be uniquely correlated with a pre-determined authentication image, which could be more easily authenticated than the POM. Numerical simulations and optical experimental results are provided to demonstrate the feasibility of the proposed method.

A quantum public-key cryptosystem without quantum channels between any two users using non-orthogonal states is provided in this paper. Every user keeps a set of quantum particles in non-orthogonal states in a key management center (KMC) as the public key while he or she keeps the states of them as the private key. By the help of KMC users can accomplish secret communication and message authentication. The laws of quantum physics guarantee the unconditional security of this cryptosystem. No entangled states or complex quantum operations are needed. On the other hand there are no quantum channels needed to connecting any two users. So the public-key cryptosystem is easier to carry out and more robust in practice.

This paper firstly briefed the basic concepts of N public key cryptosystem, RS code and QC-LDPC code, and then put forward the cascade cryptosystem with the RS code being the outer code and QC-LDPC code being the internal code. At last, the writer analyzed in detail the security and performance of the N cryptosystem based on double public key, and thus proved its better security and performance than the traditional public key cryptosystem based on error correcting code. In addition, it is also endowed with higher practicability in complex environment.

Certificateless public key cryptosystem (CLPKC) improves the identity based public key cryptosystem to be key-escrow free. Many research works on CLPKC have been presented so far. However, the revocation problem in CLPKC still lacks effective solutions. The current revocation approaches suffer from either low efficiency or security weakness. In this study, we propose the first ‘scalable revocable’ certificateless encryption (RCLE) scheme against ‘decryption key exposure’. The scheme is provably secure in the standard model. Moreover, we give a second interesting RCLE scheme whose decryption key is very short.

In 1984, Shamir [1] introduced the concept of an identity-based cryptosystem. In this system, each user needs to visit a public key generation (PKG) and identify himself before joining a communication network. Once a user is accepted, the PKG will provide him with a secret key. In this way, if a user wants to communicate with others, he only needs to know the “identity” of his communication partner and the public key of the PKG. There is no public file required in this system. However, Shamir did not succeed in constructing an identity based cryptosystem, but only in constructing an identity-based signature scheme. Meshram and Meshram [5] have proposed an identity-based beta cryptosystem, security under the generalized discrete logarithm problem with distinct discrete exponents in the multiplicative group of finite fields and integer factorization problem. In this paper, we propose some modification in identity-based beta cryptosystem based on generalized discrete logarithm problem with distinct discrete exponents in the multiplicative group of finite fields and integer factorization problem and we consider the security against a conspiracy of some entities in the proposed system and show the possibility of establishing a more secure system.

Public-key cryptography can be claimed as the greatest and an excellent revolution in the field of cryptography. A public-key cryptosystem is used for both confidentiality and authentication. One such public-key cryptosystem is the RSA cryptosystem. In this paper, a modified and an enhanced scheme based on RSA public-key cryptosystem is developed. The proposed algorithm makes use of four large prime numbers which increases the complexity of the system as compared to traditional RSA algorithm which is based on only two large prime numbers. In the proposed Enhanced and Secured RSA Key Generation Scheme (ESRKGS), the public component n is the product of two large prime numbers but the values of Encryption (E) and Decryption (D) keys are based on the product of four large prime numbers (N) making the system highly secured. With the existing factorization techniques, it is possible only to find the primes p and q. The knowledge of n alone is not sufficient to find E and D as they are based on N. The time required for cryptanalysis of ESRKGS is higher than traditional RSA cryptosystem. Thus the system is highly secure and not easily breakable. A comparison is done between the traditional RSA scheme, a recent RSA modified scheme and our scheme to show that the proposed technique is efficient.

Without proper and well-managed encryption, digital communications interception is technically easy to tap over public networks, and it causes unauthorized disclosure of sensitive information and irreparable harm to individuals as well as organizations. To ensure that digital information remains complete, accessible and secure at all times, it needs to be reliably processed on security measures at both the sending and receiving ends. Signcryption like other aspects of a cryptographic system simultaneously provides the characteristics of both digital signature and encryption and can fulfill the basic security requirements of information confidentiality, integrity and availability in transmission. In this paper, we introduce a threshold signcryption scheme based on elliptic curve cryptography to combine the dynamic knapsack cryptosystem technique with the Chinese remainder theorem and achieve a more robust security cryptosystem for multi-document transmission. With the proposed composition scheme of threshold signcryption function, participants not only can employ the avalanche effect of unsystematic properties founded on the elliptic curve cryptography's point addition to chaotically generate pre-shared secure cipher keys against the counterfeiting or potential information leakage problems but also apply the advantages of a smaller key size and its high strength of security under the elliptic curve discrete logarithm problem assumption to carry out digital communications, which can be fast and reliably transmitted over a public channel. Copyright © 2014 John Wiley & Sons, Ltd.

The applications of using multi-tag RFID technology have rapidly grown to be used in different fields of life. However, security and privacy are the main issues with this technology. In RFID multi-tags applications, a number of tags need to be securely authenticated. Although, various authentication protocols have been proposed, most of these protocols still lack of providing enough security and privacy levels. In order to overcome the security and privacy issues, this paper discusses the implementation of high-performance 256 bit elliptical curve cryptography (ECC) based system with ElGamal threshold cryptosystem. The security and privacy levels are ensured by providing a 256 bit ECC with Shamir Secret sharing scheme to distribute secure information amongst multiple RFID tags. For ensuring integrity of the data, the Keccak hash function has been used in the authentication phases

Cryptography is the essential component in any protocols for securing the communication. Diffie and Hellman introduced the concept of Public key cryptosystem, which uses two different keys for secure communication. Ralph Merkle and Martin Hellman invented a public-key cryptosystem named as Merkle-Hellman Knapsack Cryptosystem (MHKC) which is an NP-complete combinatorial problem believed that computationally difficult to solve by intruders. All the public key elements are the modulus of multiples of super increasing sequence. Adi Shamir performs cryptanalysis and breaks the MHKC in polynomial time. In this paper, a novel public key cryptosystem based on MHKC (NPKC-MHKC) has been proposed, which is secure than MHKC. NPKC-MHKC consists of Public key, Private key, and Session key. Since all the three keys depend on each other, it is computationally infeasible for the intruder to break the cryptosystem. The performance analysis shows that the execution time of NPKC-MHKC is comparatively lesser than MHKC and security analysis proves that NPKC-MHKC is secure than MHKC. So, NPKC-MHKC can be implemented in High-performance computing applications.