Signcryption schemes with threshold unsigncryption, and applications

The final publication is available at link.springer.comThe goal of a signcryption scheme is to achieve the same functionalities as encryption and signature together, but in a more efficient way than encrypting and signing separately. To increase security and reliability in some applications, the unsigncryption phase can be distributed among a group of users, through a (t, n)-threshold process. In this work we consider this task of threshold unsigncryption, which has received very few attention from the cryptographic literature up to now (maybe surprisingly, due to its potential applications). First we describe in detail the security requirements that a scheme for such a task should satisfy: existential unforgeability and indistinguishability, under insider chosen message/ciphertext attacks, in a multi-user setting. Then we show that generic constructions of signcryption schemes (by combining encryption and signature schemes) do not offer this level of security in the scenario of threshold unsigncryption. For this reason, we propose two new protocols for threshold unsigncryption, which we prove to be secure, one in the random oracle model and one in the standard model. The two proposed schemes enjoy an additional property that can be very useful. Namely, the unsigncryption protocol can be divided in two phases: a first one where the authenticity of the ciphertext is verified, maybe by a single party; and a second one where the ciphertext is decrypted by a subset of t receivers, without using the identity of the sender. As a consequence, the schemes can be used in applications requiring some level of anonymity, such as electronic auctions.Peer ReviewedPostprint (author's final draft

Lagrangian Recurrent Steganalysis and Hyper Elliptic Certificateless Signcryption for Secure Image Transmission

Present-day evolution in communication and information technology dispenses straightforward and effortless access to data, but the most noteworthy condition is the formation of secure communication. Numerous approaches were designed for safety communication. One of the crucial approaches is image steganography. Moreover, provisioning of information security services is arrived at via cryptosystems where cryptosystems make certain the secure messages transmission between the users in an untrustworthy circumstance.  The conventional method of providing encryption and signature is said to be first signing and then encryption, but both the computation and communication costs are found to be high. A certificateless signcryption mechanism is designed to transfer the medical data or images securely. This mechanism will minimize the storage and verification costs of public key certificates. The author of this article proposes a method named Lagrangian recurrent Steganalysis and Hyper Elliptic Certificateless Signcryption for transferring the medical data or images securely. In two sections the LRS-HECS method is split. They are medical image steganalysis and certificateless signcryption. First with the Chest X-Ray images obtained as input, a Codeword Correlated Lagrangian Recurrent Neural Network-based image steganography model is applied to generate steg images. Second, to transfer the medical images securely the steg images provided as input is designed a model named a Hyper Elliptic Curve-based Certificateless Signcryption. The issue of providing the integrity and validity of the transmitted medical images and receiver anonymity is addressed by the application of Hyper Elliptic Curve. Chest X-Ray pictures were used in experimental simulations, and the findings showed that the LRS-HECS approach had more advantages over existing state-of-the-art methods in terms of higher peak signal to noise ratio with data integrity and with reduced encryption time and transmission cost

Coop-DAAB : cooperative attribute based data aggregation for Internet of Things applications

The deployment of IoT devices is gaining an expanding interest in our daily life. Indeed, IoT networks consist in interconnecting several smart and resource constrained devices to enable advanced services. Security management in IoT is a big challenge as personal data are shared by a huge number of distributed services and devices. In this paper, we propose a Cooperative Data Aggregation solution based on a novel use of Attribute Based signcryption scheme (Coop - DAAB). Coop - DAAB consists in distributing data signcryption operation between different participating entities (i.e., IoT devices). Indeed, each IoT device encrypts and signs in only one step the collected data with respect to a selected sub-predicate of a general access predicate before forwarding to an aggregating entity. This latter is able to aggregate and decrypt collected data if a sufficient number of IoT devices cooperates without learning any personal information about each participating device. Thanks to the use of an attribute based signcryption scheme, authenticity of data collected by IoT devices is proved while protecting them from any unauthorized access

Contributions to secret sharing and other distributed cryptosystems

The present thesis deals with primitives related to the eld of distributed cryptography. First, we study signcryption schemes, which provide at the same time the functionalities of encryption and signature, where the unsigncryption operation is distributed. We consider this primitive from a theoretical point of view and set a security framework for it. Then, we present two signcryption schemes with threshold unsigncryption, with di erent properties. Furthermore, we use their authenticity property to apply them in the development of a di erent primitive: digital signatures with distributed veri cation. The second block of the thesis deals with the primitive of multi-secret sharing schemes. After stating some e ciency limitations of multi-secret sharing schemes in an information-theoretic scenario, we present several multi-secret sharing schemes with provable computational security. Finally, we use the results in multi-secret sharing schemes to generalize the traditional framework of distributed cryptography (with a single policy of authorized subsets) into a multipolicy setting, and we present both a multi-policy distributed decryption scheme and a multi-policy distributed signature scheme. Additionally, we give a short outlook on how to apply the presented multi-secret sharing schemes in the design of other multi-policy cryptosystems, like the signcryption schemes considered in this thesis. For all the schemes proposed throughout the thesis, we follow the same formal structure. After de ning the protocols of the primitive and the corresponding security model, we propose the new scheme and formally prove its security, by showing a reduction to some computationally hard mathematical problem.Avui en dia les persones estan implicades cada dia més en diferents activitats digitals tant en la seva vida professional com en el seu temps lliure. Molts articles de paper, com diners i tiquets, estan sent reemplaçats més i més per objectes digitals. La criptografia juga un paper crucial en aquesta transformació, perquè proporciona seguretat en la comunicació entre els diferents participants que utilitzen un canal digital. Depenent de la situació específica, alguns requisits de seguretat en la comunicació poden incloure privacitat (o confidencialitat), autenticitat, integritat o no-repudi. En algunes situacions, repartir l'operació secreta entre un grup de participants fa el procés més segur i fiable que quan la informació secreta està centralitzada en un únic participant; la criptografia distribuïda és l’àrea de la criptografia que estudia aquestes situacions. Aquesta tesi tracta de primitives relacionades amb el camp de la criptografia distribuïda. Primer, estudiem esquemes “signcryption”, que ofereixen a la vegada les funcionalitats de xifrat i signatura, on l'operació de “unsigncryption” està distribuïda. Considerem aquesta primitiva des d’un punt de vista teòric i establim un marc de seguretat per ella. Llavors, presentem dos esquemes “signcryption” amb operació de “unsigncryption” determinada per una estructura llindar, cada un amb diferents propietats. A més, utilitzem la seva propietat d’autenticitat per desenvolupar una nova primitiva: signatures digitals amb verificació distribuïda. El segon bloc de la tesi tracta la primitiva dels esquemes de compartició de multi-secrets. Després de demostrar algunes limitacions en l’eficiència dels esquemes de compartició de multi-secrets en un escenari de teoria de la informació, presentem diversos esquemes de compartició de multi-secrets amb seguretat computacional demostrable. Finalment, utilitzem els resultats obtinguts en els esquemes de compartició de multi-secrets per generalitzar el paradigma tradicional de la criptografia distribuïda (amb una única política de subconjunts autoritzats) a un marc multi-política, i presentem un esquema de desxifrat distribuït amb multi-política i un esquema de signatura distribuïda amb multi-política. A més, donem indicacions de com es poden aplicar els nostres esquemes de compartició de multi-secrets en el disseny d’altres criptosistemes amb multi-política, com per exemple els esquemes “signcryption” considerats en aquesta tesi. Per tots els esquemes proposats al llarg d’aquesta tesi, seguim la mateixa estructura formal. Després de definir els protocols de la primitiva primitius i el model de seguretat corresponent, proposem el nou esquema i demostrem formalment la seva seguretat, mitjançant una reducció a algun problema matemàtic computacionalment difícil

On the joint security of signature and encryption schemes under randomness reuse: efficiency and security amplification

Lecture Notes in Computer Science, 7341We extend the work of Bellare, Boldyreva and Staddon on the systematic analysis of randomness reuse to construct multi-recipient encryption schemes to the case where randomness is reused across different cryptographic primitives. We find that through the additional binding introduced through randomness reuse, one can actually obtain a security amplification with respect to the standard black-box compositions, and achieve a stronger level of security. We introduce stronger notions of security for encryption and signatures, where challenge messages can depend in a restricted way on the random coins used in encryption, and show that two variants of the KEM/DEM paradigm give rise to encryption schemes that meet this enhanced notion of security. We obtain the most efficient signcryption scheme to date that is secure against insider attackers without random oracles.(undefined

Development of Time-Stamped Signcryption Scheme and its Application in E-Cash System

A signcryption scheme combining public key encryptions and digital signatures in one logical step can simultaneously satisfy the security requirements of confidentiality, integrity, authenticity and non-repudiation and with a cost significantly lower than that required by the traditional "signature followed by encryption" approach. This thesis presents a new generic concept of time-stamped signcryption scheme with designated verifiability. Here an authenticated time-stamp is associated with the signcrypted text which can only be verifiable by a specific person, known as the designated verifier. The time-stamp is provided by a trusted third party, namely, Time Stamping System (TSS). The scheme is proved to be secure, as, no one, not even the signcrypter or TSS can produce a valid signcrypted text on behalf of them. We analyzed the security of the proposed scheme and found that it can withstand some active attacks. This scheme is resistant against both inside and outside attacks. The security of our scheme is based upon the hardness of solving Computational Diffie Hellman Problem (CDH), Discrete Logarithm Problem (DLP) and Integer Factorization Problem (IFP). The proposed scheme is suitable in scenarios such as, on-line patent submission, on-line lottery, e-cash, e-bidding and other e-commerce applications. Also we propose an e-cash system based on our proposed time-stamped signcryption scheme which confirms the notion of e-cash securities like anonymity of the spender, unforgeablity of the digital coin, prevention of double spending

New Conditional Privacy-preserving Encryption Schemes in Communication Network

Nowadays the communication networks have acted as nearly the most important fundamental infrastructure in our human society. The basic service provided by the communication networks are like that provided by the ubiquitous public utilities. For example, the cable television network provides the distribution of information to its subscribers, which is much like the water or gas supply systems which distribute the commodities to citizens. The communication network also facilitates the development of many network-based applications such as industrial pipeline controlling in the industrial network, voice over long-term evolution (VoLTE) in the mobile network and mixture reality (MR) in the computer network, etc. Since the communication network plays such a vital role in almost every aspect of our life, undoubtedly, the information transmitted over it should be guarded properly. Roughly, such information can be categorized into either the communicated message or the sensitive information related to the users. Since we already got cryptographical tools, such as encryption schemes, to ensure the confidentiality of communicated messages, it is the sensitive personal information which should be paid special attentions to. Moreover, for the benefit of reducing the network burden in some instances, it may require that only communication information among legitimated users, such as streaming media service subscribers, can be stored and then relayed in the network. In this case, the network should be empowered with the capability to verify whether the transmitted message is exchanged between legitimated users without leaking the privacy of those users. Meanwhile, the intended receiver of a transmitted message should be able to identify the exact message sender for future communication. In order to cater to those requirements, we re-define a notion named conditional user privacy preservation. In this thesis, we investigate the problem how to preserve user conditional privacy in pubic key encryption schemes, which are used to secure the transmitted information in the communication networks. In fact, even the term conditional privacy preservation has appeared in existing works before, there still have great differences between our conditional privacy preservation definition and the one proposed before. For example, in our definition, we do not need a trusted third party (TTP) to help tracing the sender of a message. Besides, the verification of a given encrypted message can be done without any secret. In this thesis, we also introduce more desirable features to our redefined notion user conditional privacy preservation. In our second work, we consider not only the conditional privacy of the message sender but also that of the intended message receiver. This work presents a new encryption scheme which can be implemented in communication networks where there exists a blacklist containing a list of blocked communication channels, and each of them is established by a pair of sender and receiver. With this encryption scheme, a verifier can confirm whether one ciphertext is belonging to a legitimated communication channel without knowing the exact sender and receiver of that ciphertext. With our two previous works, for a given ciphertext, we ensure that no one except its intended receiver can identify the sender. However, the receiver of one message may behave dishonest when it tries to retrieve the real message sender, which incurs the problem that the receiver of a message might manipulate the origin of the message successfully for its own benefit. To tackle this problem, we present a novel encryption scheme in our third work. Apart from preserving user conditional privacy, this work also enforces the receiver to give a publicly verifiable proof so as to convince others that it is honest during the process of identifying the actual message sender. In our forth work, we show our special interest in the access control encryption, or ACE for short, and find this primitive can inherently achieve user conditional privacy preservation to some extent. we present a newly constructed ACE scheme in this work, and our scheme has advantages over existing ACE schemes in two aspects. Firstly, our ACE scheme is more reliable than existing ones since we utilize a distributed sanitizing algorithm and thus avoid the so called single point failure happened in ACE systems with only one sanitizer. Then, since the ciphertext and key size of our scheme is more compact than that of the existing ACE schemes, our scheme enjoys better scalability

An efficient FIS and RSA based Signcryption Security Scheme

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An Efficient Online/Offline Signcryption Scheme for Internet of Things in Smart Home

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A Comprehensive Survey on Signcryption Security Mechanisms in Wireless Body Area Networks

WBANs (Wireless Body Area Networks) are frequently depicted as a paradigm shift in healthcare from traditional to modern E-Healthcare. The vitals of the patient signs by the sensors are highly sensitive, secret, and vulnerable to numerous adversarial attacks. Since WBANs is a real-world application of the healthcare system, it’s vital to ensure that the data acquired by the WBANs sensors is secure and not accessible to unauthorized parties or security hazards. As a result, effective signcryption security solutions are required for the WBANs’ success and widespread use. Over the last two decades, researchers have proposed a slew of signcryption security solutions to achieve this goal. The lack of a clear and unified study in terms of signcryption solutions can offer a bird’s eye view of WBANs. Based on the most recent signcryption papers, we analyzed WBAN’s communication architecture, security requirements, and the primary problems in WBANs to meet the aforementioned objectives. This survey also includes the most up to date signcryption security techniques in WBANs environments. By identifying and comparing all available signcryption techniques in the WBANs sector, the study will aid the academic community in understanding security problems and causes. The goal of this survey is to provide a comparative review of the existing signcryption security solutions and to analyze the previously indicated solution given for WBANs. A multi-criteria decision-making approach is used for a comparative examination of the existing signcryption solutions. Furthermore, the survey also highlights some of the public research issues that researchers must face to develop the security features of WBANs.publishedVersio