Threshold Cryptography Research Articles

Enabling Privacy in Vehicle-to-Grid Interactions for Battery Recharging

The diffusion of Electric Vehicles (EV) fostered by the evolution of the power system towards the new concept of Smart Grid introduces several technological challenges related to the synergy among electricity-propelled vehicle fleets and the energy grid ecosystem. EVs promise to reduce carbon emissions by exploiting Renewable Energy Sources (RESes) for battery recharge, and could potentially serve as storage bank to flatten the fluctuations of power generation caused by the intermittent nature of RESes by relying on a load aggregator, which intelligently schedules the battery charge/discharge of a fleet of vehicles according to the users’ requests and grid’s needs. However, the introduction of such vehicle-to-grid (V2G) infrastructure rises also privacy concerns: plugging the vehicles in the recharging infrastructures may expose private information regarding the user’s locations and travelling habits. Therefore, this paper proposes a privacy-preserving V2G infrastructure which does not disclose to the aggregator the current battery charge level, the amount of refilled energy, nor the time periods in which the vehicles are actually plugged in. The communication protocol relies on the Shamir Secret Sharing threshold cryptosystem. We evaluate the security properties of our solution and compare its performance to the optimal scheduling achievable by means of an Integer Linear Program (ILP) aimed at maximizing the ratio of the amount of charged/discharged energy to/from the EV’s batteries to the grid power availability/request. This way, we quantify the reduction in the effectiveness of the scheduling strategy due to the preservation of data privacy.

Fully distributed certificate authority based on polynomial over elliptic curve for MANET

A mobile ad hoc network (MANET) is a wireless communication network, which does not rely on any centralized management or a pre-existing infrastructure. Various certificate authorities (CAs) distributed over the network, each with a periodically updated share of the secrete key, is usually adopted. Thus many efforts have been made to adapt Certificate Authority's (CA) tasks to the dynamic environments of MANETs and distribute the tasks of CA among MANET nodes. Elliptic Curve Cryptography (ECC) is a cryptographic technique prominent suited for small devices, like those used in wireless communications, and is gaining momentum. The main advantage of ECC versus RSA is that for the same level of security it requires a much shorter key length. The purpose of this work is to design and implement a fully certificate authority based on polynomial over elliptic curve, based on trust graphs and threshold cryptography, which though has better cryptography in nature. The security is based on the elliptic curve discrete logarithm problem which aimed to increase the authentication and the security in MANETs.

Asynchronous Secret Reconstruction and Its Application to the Threshold Cryptography

In Shamir’s(t,n) threshold of the secret sharing scheme, a secret is divided into n shares by a dealer and is shared among n shareholders in such a way that (a) the secret can be reconstructed when there are t or more than t shares; and (b) the secret cannot be obtained when there are fewer than t shares. In the secret reconstruction, participating users can be either legitimate shareholders or attackers. Shamir’s scheme only considers the situation when all participating users are legitimate shareholders. In this paper, we show that when there are more than t users participating and shares are released asynchronously in the secret reconstruction, an attacker can always release his share last. In such a way, after knowing t valid shares of legitimate shareholders, the attacker can obtain the secret and therefore, can successfully impersonate to be a legitimate shareholder without being detected. We propose a simple modification of Shamir’s scheme to fix this security problem. Threshold cryptography is a research of group-oriented applications based on the secret sharing scheme. We show that a similar security problem also exists in threshold cryptographic applications. We propose a modified scheme to fix this security problem as well.

Методы пороговой криптографии для защиты облачных вычислений

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.

Enhancing Security for Mobile Ad hoc Networks by Using Identity Based Cryptography

This paper studies key management and security issues in mobile ad hoc networks (MANETs). Lack of strong identification results in unauthorized entities access to the sensitive data, and leads to loos of confidentiality and integrity, which causes many vulnerabilities and attacks in the network .We present the key management scheme as a combination of Identity-Based (User’s Identification), Unique Transmission’s time Factor and Threshold Cryptography for ad hoc networks. It is a certificateless solution which eliminates the need for public key distribution and certificates in public key management schemes. This scheme is also efficient in computation since small unique factor enhance the authentication of entities.

SECURING CLUSTER BASED ADHOC NETWORK THROUGH BALANCED CLUSTERING WITH DISTRIBUTION AUTHORITIES OF KEY DISTRIBUTION AND KEY MANAGEMENT USING DEPLOYMENT KNOWLEDGE.

In this paper, we address key management in cluster -based mobile ad hoc networks (MANETs). We present a fully-distributed IDbased multiple secrets key management scheme (IMKM) . This scheme is implemented via a combination of I D-based multiple secrets and threshold cryptography. Ensuring secure communi cation in an ad hoc network is extremely challengin g because of the dynamic nature of the network and the lack of centralized m anagement. Our proposed analysis includes the effec t of packet generation model, random deployment of sensors, dynamic cluster head assignment, data compression, and energy consumptio n model at the sensors. a new protocol called Equalized Cluster Head Election Routing Protocol (ECHERP), which pursues energy co nservation through balanced clustering, is proposed. Performance evalu ation of ECHERP is carried out through simulation t ests. We also present a novel key predistribution scheme that uses deployment kno wledge to divide deployment regions into overlappin g clusters, each of which has its own distinct key space. Through careful constru ction of these clusters, network resilience is impr oved, we focus on the management of encryption keys in large-scale clustered WSNs. W e propose a novel distributed key management scheme based on Exclusion Basis Systems (EBS); a combinatorial formulation of the g roup key management problem. Initially, clusters ar e formed in the network and the cluster heads are selected based on the energy cost, coverage and processing capacity. The sink as signs cluster key to every cluster and an EBS key set to every cluster head. T he EBS key set contains the pairwise keys for intra -cluster and inter-cluster communication. During data transmission towards the sink, the data is made to pass through two phases of encryption thus ensuring security in the network. Our results include perfor mance evaluation in terms of security metrics in cl ustered WSN and a detailed analysis of resource utilization.

Efficient fully homomorphic encryption from RLWE with an extension to a threshold encryption scheme

In this paper, we present an effective fully homomorphic encryption (FHE) from ring learning with errors (RLWE) assumption without using Gentry’s standard squashing and bootstrapping techniques. Our FHE scheme is to modify the recent FHE scheme of Brakerski. We use the re-linearization technique to reduce the length of ciphertext considerably, and use the modulus reduction technique to manage the noise level and decrease the decryption complexity without introducing additional assumptions. Furthermore, with the key-homomorphic property, we extend our FHE scheme to a threshold fully homomorphic encryption (TFHE), which allows parties to cooperatively decrypt a ciphertext without learning anything but the plaintext. The TFHE scheme can be protected from related-key attacks, as long as we add extra smudging noise during sensitive operations.

A Secure Key for Cloud using Threshold Cryptography in Kerberos

In IT industry now a days there is a need for several new resources and storage requirement for terabyte of data generated every day. Cloud Computing is a solution for this in a cost effective manner. Cloud Computing provides on demand resources as services to client. Cloud is highly scalable, flexible and platform in dependable. Although it is benefiting the clients in several ways but as data is stored remotely it has many security loopholes like attacks, data loss, other authentication and security issues. In this paper an authentication model is proposed for cloud computing based on Kerberos protocol using threshold cryptography to provide more security and to increase the availability of key. This model can also benefit by filtering the unauthorized access and to reduce the burden of computation and memory usage of cloud provider against authentication checks for each client. It acts as a third party between cloud server and clients to allow authorized and secure access to cloud services. In this paper we will take a review of related work for cloud security issues and attacks. In next section we will discuss the proposed architecture and its working. Next we will see how it can provide better security and availability to key used for

Research on Architecture Survivability of Wireless Networks

In this paper, the network architecture of wireless network systems survivability, the ideas based on intrusion tolerance, redundancy and diversity of technology will be combined, using threshold cryptography, presents a viable network server security architecture. This proposal implements key features of the system security and robustness, the database system to meet the survivability requirements for building a wireless network server architecture has important reference value.

Safeguarding ad hoc networks with a self-organized membership control system

One of the key challenges for ad hoc networks is providing distributed membership control. This paper introduces a self-organized mechanism to control user access to ad hoc networks without requiring any infrastructure or a central administration entity. Our mechanism authenticates and monitors nodes with a structure that we call controller set, which is robust to the dynamic network membership. We develop analytical models for evaluating the proposal and validate them through simulations. The analysis shows that the proposed scheme is robust even to collusion attacks and provides availability up to 90% better than proposals based on threshold cryptography. The performance improvement arises mostly from the controller sets capability to recover after network partitions and from the identification and exclusion of malicious nodes.

A Distributed Approach of a Threshold Certificate-Based Encryption Scheme with No Trusted Entities

ABSTRACT The distributed paradigm as manifested in distributed networks, calls for a different way from the traditional client-server model for providing Trusted third party (TTP) services to strengthen security. Certificate Authorities (CAs) are among the most common such TTP. Generating certified keys and manage certification information (the basic functionality of a CA) in a fully distributed manner is a key challenge in the distributed IT environment. Current approaches are based on the use of trusted entities within the distributed system that constitute single points of failure and follow complex certificate management and revocation mechanisms capable of hindering their adoption in a large scale. The hardware resources cost of each distributed system member committed to realizing and maintaining such certificate authority system can be high. Furthermore, distributed CA approaches lack flexibility when it come to dynamic member behavior such as dynamic member joining or leaving the system, since they employ complex, computational intensive mechanisms for retaining the CA consistency during such activity. In this paper, we propose the combination of a distributed key generation threshold cryptography scheme along with an efficient secure certificate-based encryption scheme to provide a solution that matches the above problems. The outcome of this proposal is a distributed Threshold Certificate-Based Encryption Scheme that has no need for any centralized trusted entity to create, and split secrets or distribute keys-certificates at any point during its operating cycle. The proposed scheme has few requirements concerning certificate management due to its inherited Certificate-based Encryption features which enables the scheme's participants to use their certificates as keys and has an easy participant addition-removal mechanism to support dynamic network environments. Extending the work done in (Fournaris, 2012), in this paper the proposed distributed Certificate Authority and encryption/decryption scheme is described and analyzed, participant addition and removal mechanisms as detailed and the scheme's security and performance is discussed. Performance characterization reveals that our scheme is very efficient in terms of computational intensive and resource constraining operations like Elliptic Curve point multiplication and bi-linear pairing.

Hierarchical Group Key Management using Threshold Cryptography in Wireless Sensor Networks

wireless sensor networks (WSNs), data transmission is secured by authenticating secret keys. Secure key management is most important for network reliability and consistency. In this paper, a hierarchical group key management technique using threshold cryptography in Wireless Sensor Networks is proposed. The technique considers hierarchical sensor network, where sensing nodes are coordinated by forwarding nodes (FN) and in turn they are connected to the BS which is responsible for key computation and distribution. FN estimates the group key using threshold secret sharing scheme. The acquired group key is divided into multiple shares and shared among member nodes. Thus, this reduces the possibility of key compromised. The proposed technique is simulated using network simulator 2 (NS-2). Simulation results show the proficiency of the technique.

On Access Security in Cloud Computing

Currently cloud computing brings along a lot of positive changes to our life, and at the same time it does lead to a lot of security concerns. In order to overcome these concerns, in this paper we first introduce system under study; second, we reduce the group authentication steps for key distribution by means of TPM-based certificates; third, we leverage the identity-based threshold cryptography to avoid single-point-of-failure; last, we design experiments to test our scheme and give related explanations.

Quantum password sharing scheme using trusted servers

The main purpose of the sharing schemes based on trusted servers is to obtain a password. The threshold cryptography aims the secret cryptographic protection, and is based on the distribution of the key on several servers, with the purpose to tolerate the attacks. In this work I will present a quantum version of the password sharing protocol, using a number n of trustful servers, to assure its security. The model I propose approaches the issue of the distribution of the authentication key between a client and n-1 servers.

Towards Practical Communication in Byzantine-Resistant DHTs

There are several analytical results on distributed hash tables (DHTs) that can tolerate Byzantine faults. Unfortunately, in such systems, operations such as data retrieval and message sending incur significant communication costs. For example, a simple scheme used in many Byzantine fault-tolerant DHT constructions of n nodes requires O(log3 n) messages; this is likely impractical for real-world applications. The previous best known message complexity is O(log2 n) in expectation. However, the corresponding protocol suffers from prohibitive costs owing to hidden constants in the asymptotic notation and setup costs. In this paper, we focus on reducing the communication costs against a computationally bounded adversary. We employ threshold cryptography and distributed key generation to define two protocols, both of which are more efficient than existing solutions. In comparison, our first protocol is deterministic with O(log2 n) message complexity, and our second protocol is randomized with expected O(log n) message complexity. Furthermore, both the hidden constants and setup costs for our protocols are small, and no trusted third party is required. Finally, we present results from microbenchmarks conducted over PlanetLab showing that our protocols are practical for deployment under significant levels of churn and adversarial behavior.

Adaptively secure non-interactive threshold cryptosystems

Threshold cryptography aims at enhancing the availability and security of decryption and signature schemes by splitting private keys into several (say n) shares (typically, each of size comparable to the original secret key). In these schemes, a quorum of at least (d≤n) servers needs to act upon a message to produce the result (decrypted value or signature), while corrupting less than d servers maintains the scheme’s security. For about two decades, extensive study was dedicated to this subject, which created a number of notable results. So far, most practical threshold signatures, where servers act non-interactively, were analyzed in the limited static corruption model (where the adversary chooses which servers will be corrupted at the system’s initialization stage). Existing threshold encryption schemes that withstand the strongest combination of adaptive malicious corruptions (allowing the adversary to corrupt servers at any time based on its complete view), and chosen-ciphertext attacks (CCA) all require interaction (in the non-idealized model) and attempts to remedy this problem resulted only in relaxed schemes. The same is true for threshold signatures secure under chosen-message attacks (CMA). To date (for about 10 years), it has been open whether there are non-interactive threshold schemes providing the highest security (namely, CCA-secure encryption and CMA-secure signature) with scalable shares (i.e., as short as the original key) and adaptive security. This paper answers this question affirmatively by presenting such efficient decryption and signature schemes within a unified algebraic framework.

Practical distributed secret key generation for delay tolerant networks

SUMMARYDelay tolerant networks (DTNs) are resource‐constrained dynamic networks where a continuous end‐to‐end connectivity is not always available. In such a challenging network, a fixed infrastructure may not be connected when a DTN is partitioned or the message delay in the network is large. Thus, the traditional public key infrastructure system and identity‐based encryption (IBE) system are not suitable for DTNs because they rely on centralized infrastructures and require multiple round‐trip interactions. To address this issue, we propose a distributed secret key generation system with self‐certified identity (SCI‐DKG) that does not require any private key generator and threshold cryptosystem. Initially, each node generates a private key and distributes an initial message including a self‐certified identity and secret sharings to members in a DTN. Receivers independently authenticate the identity and extracts some encryption parameters corresponding to the identity from this initial message. We prove that SCI‐DKG is chosen ciphertext secure in the standard model, and it can resist potential network attacks. Simulation results show that SCI‐DKG has smaller delay and higher successful ratio of secret key generation compared with IBE and hierarchical IBE systems implemented in a DTN. Copyright © 2012 John Wiley & Sons, Ltd.

An efficient identity-based secret key management scheme for MANETs

This paper put forward an identity-based key management scheme for mobile ad hoc networks (MANETs), it provids an efficient secret key management mechanism for security schemes, which be implemented over any cyclic group in that the strong Diffie-Hellman problem is supposed to be hard. By employing identity-based and threshold cryptography, the proposed scheme eliminates the burden of certificates management and can be high level tolerance to node compromise. The scheme is based on threshold Schnorr signature (TSch), for higher efficiency, we transform TSch to a simpler form, donated by SimpleTSch, and prove that SimpleTSch is unforgeable under passive attacks in the random oracle model. However, to cope with active attacks, we enforce the security by introducing Fiore et al's key agreement. We can say that the proposed key management scheme gives lots of help for design of security protocols in MANETs.

Virtual private key generator based escrow‐free certificateless public key cryptosystem for mobile ad hoc networks

ABSTRACTA certificateless public key cryptosystem can make a special contribution to building key distribution and management architecture in resource‐constrained mobile ad hoc networks (MANETs) because it has no separate certificate and no complex certificate management problems. In this paper, we present a virtual private key generator (VPKG)‐based escrow‐free certificateless public key cryptosystem as a novel combination of certificateless and threshold cryptography. Using secret sharing, we build a VPKG whose members collaboratively calculate the partial private key and send it to the user via public channels. The private key of a user is generated jointly by the VPKG and the user. Each of them has “half” of the secret information about the private key of the user. In addition, binding a user's public key with its identity and partial private key, respectively, raises our schemes to the same trust level as is enjoyed in a traditional public key infrastructure. We also show that the proposed scheme is secure against public key replacement attacks and passive attacks. Copyright © 2012 John Wiley & Sons, Ltd.

Guest Editorial: Computing and Combinatorics

“Computing and Combinatorics” is an interesting and fundamental research area, which involves several fields, ranging from algorithms, theory of computation, and computational complexity to combinatorics related to computing. This issue consists of six papers, which are briefly discussed as follows. The “Shorthand Universal Cycles for Permutations” paper investigates SP-cycles with maximum and minimum ’weight’. The authors show that periodic min-weight SP-cycles correspond to spanning trees of the (n− 1) permutohedron and provides two constructions by using ’half-hunts’ from bell-ringing and the cool-lex order. In “Zero-Knowledge Argument for Simultaneous Discrete Logarithms,” the authors present an EQDL (the equality of two discrete logarithms) protocol in the ROM (random oracle model) which saves approximately 40 % of the computational cost and approximately 33 % of the prover’s outgoing message size. This improvement benefits a variety of interesting cryptosystems, ranging from signatures and anonymous credential systems, to verifiable secret sharing and threshold cryptosystems. The issue also includes the study of computational complexity. Namely, the paper “Tile-Packing Tomography is NP-hard” shows that for a fixed tile, it is NP-hard to reconstruct its tilings from their projections for all types of tiles. The #NC1 upper bound for the problem of counting accepting paths in any fixed visibly pushdown automaton is considered in “Counting paths in VPA is complete for #NC1”. The paper also shows that the difference between #BWBP and #NC1 is captured exactly by the addition of a visible stack to a nondeterministic finite-state automaton. Due to the NP-hardness of the problems, approximation algorithms are needed to provide a near-optimal solution. In “Exact and Approximation Algorithms for Geometric and General Capacitated Set Cover Problems”, the first known polynomial-