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Giesecke & Devrient s'encarrega, entre moltes altres coses, de desenvolupar sistemes operatius incrustats per a dispositius de diferents clients. Quan aquests s'han d'actualitzar, s'ha d'enviar el nou sistema operatiu al client garantint que en cap moment es veurà compromès. És per això que es vol millorar la seguretat de l'eina que s'encarrega de generar la nova imatge. Actualment, les claus utilitzades per encriptar i signar la nova imatge es guarden en pla i es volen moure a un HSM. Per fer-ho, s'han mogut les claus necessàries al dispositiu mencionat i s'han implementat els canvis necessaris a l'eina per tal que es pugui connectar a l'HSM, obtenir les claus i fer les operacions criptogràfiques necessàries. Giesecke & Devrient is responsible, among many other things, for developing embedded operating systems for different customer devices. When these need to be updated, the new operating system must be sent to the customer, guaranteeing that it will not be compromised. For that reason we want to improve the security of the tool responsible for generating the new image. Currently, the keys used to encrypt and sign the new image are stored in plain, and we want to move them to an HSM. To do this, the required keys have been moved to the device in question, and the needed adaptations have been implemented in the tool so that it can connect to the HSM, obtain the keys and perform the necessary cryptographic operations.

The classic Elliptic curve digital Signature Algorithm (ECDSA) uses one inversion operation in the process of signature and verification, which greatly reduces the efficiency of digital signatures. Up to now, most research schemes improve efficiency by reducing reverse operations, but they fail to attach importance to such issues as forgery signature attack. At the same time, in the blockchain, the weak randomness of ECDSA will lead to the attack of forging random numbers, which is a potential problem of digital currency transactions. In consideration of this reason, in this article, an improved provably secure elliptic curve digital signature scheme is constructed. First, the new scheme introduces double parameters in the signature process, that can effectively resist the weak randomness attack of ECDSA in Bitcoin, and can be applied to blockchain digital currency trading systems. Second, in the random oracle model, it is provably indistinguishable against Elliptic Curve Discrete Logarithm Problem (ECDLP) under the super type I and type II adversary. Third, the new scheme avoids the inverse operation in the signature and verification phase. Compared with the ECDSA, the running speed is optimized by 50.1%. Similarly, the proposed scheme has higher computational efficiency than other existing algorithms.

The paper considers the problem of documents identification in electronic document management systems. The relevance of this topic is justified by the widespread use of electronic document management systems which require reliable identification of transferred documents. The main problems for identifying documents in electronic document management systems are authorship confirmation, confirmation of the document immutability and determining the signing time. A review of the main methods of identification is given, their advantages and disadvantages are identified. After possible identification methods analyzing, it was found that the method based on the electronic keys allows to reliably identify the document, determine the signing time, guaranty the fact of signing and does not require significant amount of resources for sign formation and verification. This distinguishes the method of identification based on electronic keys fundamentally among others. The method is based on the elliptic curve digital signature algorithm. The reliability of the chosen algorithm is based on the problem of the discrete logarithm in the group of points of the elliptic curve. To implement the algorithm public and private keys are used. After generating a key pair, the private key is kept in secret by the user and used to sign documents, the public key is used to identify the user and should be known to all users of the system. The information support of the identification subsystem is provided. A three-level architectural model in which the client level role is performed by the application programming interface is proposed. The technologies for implementing signature algorithms are considered. Identification subsystem software has been developed. This software allows users to create both individual and built-in document signatures, as well as to verify it. The developed identification subsystem was tested using files of different formats and sizes.

The last few years have witnessed a vast evolution in the communication and computational fields. The presence of social media makes data transferring more easier, which raises a flag of unauthorized usage and redistribution of digital contents. This copyright scenario is hardly affecting the publishing rights of authors and publishers. This paper presents a robust framework that protects the copyright property where only the authorized users legally use the data and prevents the illegal using or copying of data. The proposed framework is based on Digital Right Management (DRM) and includes two robust cryptosystems; Advanced Encryption Standard (AES) and Elliptic Curve Cryptography (ECC) algorithms. The multimedia contents are encrypted using the AES-256 algorithm, while the shared key is encrypted using the ECC algorithm. The authorized user can utilize the copyrighted contents if the authorization is not expired. The license generation is done by a lightweight data-interchange format JavaScript Object Notation (JSON), and the license is validated using the Elliptic Curve Digital Signature Algorithm. The evaluation of the system has shown that it is fulfilling all the requirements of DRM technology with low cost, availability, platform independently, reliability and scalability since it is implemented on a cloud platform.

Side Channel Analysis attacks consist in, i.a., exploiting the information leaked from the implementations of cryptographic algorithms. In this paper we describe two key revealing methods which are based on machine learning algorithms: K-means and PCA. We performed the attacks against ECDSA implementations without any prior knowledge about the key and achieved 100% accuracy for an implementation without any countermeasures against horizontal attacks and 88.7% accuracy for an implementation with bus address sequencing. In the scenario where the kP operation inputs are controlled by the attacker (as during signature verification), we achieved 98.3% accuracy for the implementation with countermeasures.

It is well known that conventional digital signature algorithms such as RSA and ECDSA are vulnerable to quantum computing attacks. Hash-based signature schemes are attractive as post-quantum signature schemes in that it is possible to calculate the quantitative security level and the security is proven. SPHINCS is a stateless hash-based signature scheme and introduces HORST few-time signature scheme which is an improvement of HORS. However, HORST as well as HORS suffers from pretty large signature sizes. HORSIC is proposed to reduce the signature size, yet does not provide in-depth security analysis. In this paper, we propose HORSIC+, which is an improvement of HORSIC. HORSIC+ differs from HORSIC in that HORSIC+ does not apply f as a plain function to the signature key, but uses a member of a function family. In addition, HORSIC+ uses the chaining function similar to W-OTS+. These enable the strict security proof without the need for the used function family to be a permutation or collision resistant. HORSIC+ is existentially unforgeable under chosen message attacks, assuming a second-preimage resistant family of undetectable one-way functions and cryptographic hash functions in the random oracle model. HORSIC+ reduces the signature size by as much as 37.5% or 18.75% compared to HORS and by as much as 61.5% or 45.8% compared to HORST for the same security level.

Although digital signature has been a fundamental technology for cryptosystems, it still draws considerable attention from both academia and industry due to the recent raising interest in blockchains. This article revisits the subliminal channel existing digital signature and reviews its abuse risk of the constructor’s private key. From a different perspective on the subliminal channel, we find the new concept named the chamber of secrets in blockchains. The found concept, whereby the secret is hidden and later recovered by the constructor from the common transactions in a blockchain, highlights a new way to encourage implementing various applications to benefit efficiency and security. Thus, the proposed scheme benefits from the following advantages: (1) avoiding the high maintenance cost of certificate chain of certificate authority, or public key infrastructure, and (2) seamlessly integrating with blockchains using the property of chamber of secrets. In order to easily understand the superiority of this new concept, a remote authentication scenario is taken as a paradigm of IoT to demonstrate that the further advantages are achieved: (1) avoiding high demand for storage space in IoT devices, and (2) avoiding maintaining a sensitive table in IoT server.

Proactive security is the notion of defending a distributed system against an attacker who compromises different devices through its lifetime, but no more than a threshold number of them at any given time. The emergence of threshold wallets for more secure cryptocurrency custody warrants an efficient proactivization protocol tailored to this setting. While many proactivization protocols have been devised and studied in the literature, none of them have communication patterns ideal for threshold wallets. In particular a (t, n) threshold wallet is designed to have t parties jointly sign a transaction (of which only one may be honest) whereas even the best current proactivization protocols require at least an additional t-1 honest parties to come online simultaneously to refresh the system.In this work we formulate the notion of refresh with offline devices, where any tρ parties may proactivize the system at any time and the remaining n-tρ offline parties can non-interactively "catch up"at their leisure. However, many subtle issues arise in realizing this pattern. We identify that this problem is divided into two settings: (2, n) and (t, n) where t > 2. We develop novel techniques to address both settings as follows:•We show that the (2, n) setting permits a tight tρ for refresh. In particular we give a highly efficient tρ = 2 protocol to upgrade a number of standard (2, n) threshold signature schemes to proactive security with offline refresh. This protocol can augment existing implementations of threshold wallets for immediate use- we show that proactivization does not have to interfere with their native mode of operation. This technique is compatible with Schnorr, EdDSA, and with some effort even sophisticated ECDSA protocols. By implementation we show that proactivizing two different recent (2, n) ECDSA protocols incurs only 14% and 24% computational overhead respectively, less than 200 bytes, and no extra round of communication.•For the general (t, n) setting we prove that it is impossible to construct an offline refresh protocol with tρ < 2(t-1), i.e. tolerating a dishonest majority of online parties. Our techniques are novel in reasoning about the message complexity of proactive security, and may be of independent interest.Our results are positive for small-scale decentralization (such as 2FA with threshold wallets), and negative for large-scale distributed systems with higher thresholds. We thus initiate the study of proactive security with offline refresh, with a comprehensive treatment of the dishonest majority case.

We propose Black-Box IoT (BBox-IoT), a new ultra-lightweight black-box system for authenticating and storing IoT data. BBox-IoT is tailored for deployment on IoT devices (including low-Size Weight and Power sensors) which are extremely constrained in terms of computation, storage, and power. By utilizing core Blockchain principles, we ensure that the collected data is immutable and tamper-proof while preserving data provenance and non-repudiation. To realize BBox-IoT, we designed and implemented a novel chain-based hash signature scheme which only requires hashing operations and removes all synchronicity dependencies between signer and verifier. Our approach enables low-SWaP devices to authenticate removing reliance on clock synchronization. Our evaluation results show that BBox-IoT is practical in Industrial Internet of Things (IIoT) environments: even devices equipped with 16MHz micro-controllers and 2KB memory can broadcast their collected data without requiring heavy cryptographic operations or synchronicity assumptions. Finally, when compared to industry standard ECDSA, our approach is two and three orders of magnitude faster for signing and verification operations respectively. Thus, we are able to increase the total number of signing operations by more than 5000% for the same amount of power., To appear in IoTDI2021

International audience; In 2003, Fischlin introduced the concept of progressive verification in cryptography to relate the error probability of a cryptographic verification procedure to its running time. It ensures that the verifier confidence in the validity of a verification procedure grows with the work it invests in the computation. Le, Kelkar and Kate recently revisited this approach for digital signatures and proposed a similar framework under the name of flexible signatures. We propose efficient probabilistic verification procedures for popular signature schemes in which the error probability of a verifier decreases exponentially with the ver-ifier running time. We propose theoretical schemes for the RSA and ECDSA signatures based on some elegant idea proposed by Bernstein in 2000 and some additional tricks. We also present a general practical method, that makes use of efficient error-correcting codes, for signature schemes for which verification involves a matrix/vector multiplication.

Attacking ECDSA with wNAF implementation for the scalar multiplication first requires some side channel analysis to collect information, then lattice based methods to recover the secret key. In this paper, we reinvestigate the construction of the lattice used in one of these methods, the Extended Hidden Number Problem (EHNP). We find the secret key with only 3 signatures, thus reaching a known theoretical bound, whereas best previous methods required at least 4 signatures in practice. Given a specific leakage model, our attack is more efficient than previous attacks, and for most cases, has better probability of success. To obtain such results, we perform a detailed analysis of the parameters used in the attack and introduce a preprocessing method which reduces by a factor up to 7 the total time to recover the secret key for some parameters. We perform an error resilience analysis which has never been done before in the setup of EHNP. Our construction find the secret key with a small amount of erroneous traces, up to \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$2\%$$\end{document} of false digits, and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$4\%$$\end{document} with a specific type of error.

A $(t,n)-$ threshold signature scheme enables distributed signing among $n$ players such that any subgroup of size $t$ can sign, whereas any group with fewer players cannot. Our goal is to produce signatures that are compatible with an existing centralized signature scheme: the key generation and signature algorithm are replaced by a communication protocol between the parties, but the verification algorithm remains identical to that of a signature issued using the centralized algorithm. Starting from the threshold schemes for the ECDSA signature due to R. Gennaro and S. Goldfeder, we present the first protocol that supports multiparty signatures with an offline participant during the Key Generation Phase, without relying on a trusted third party. Following well-established approaches, we prove our scheme secure against adaptive malicious adversaries., 31 pages

Performance and security are two critical functions of wireless ad-hoc networks (WANETs). Network security ensures the integrity, availability, and performance of WANETs. It helps to prevent critical service interruptions and increases economic productivity by keeping networks functioning properly. Since there is no centralized network management in WANETs, these networks are susceptible to packet drop attacks. In selective drop attack, the neighboring nodes are not loyal in forwarding the messages to the next node. It is critical to identify the illegitimate node, which overloads the host node and isolating them from the network is also a complicated task. In this paper, we present a resistive to selective drop attack (RSDA) scheme to provide effective security against selective drop attack. A lightweight RSDA protocol is proposed for detecting malicious nodes in the network under a particular drop attack. The RSDA protocol can be integrated with the many existing routing protocols for WANETs such as AODV and DSR. It accomplishes reliability in routing by disabling the link with the highest weight and authenticate the nodes using the elliptic curve digital signature algorithm. In the proposed methodology, the packet drop rate, jitter, and routing overhead at a different pause time are reduced to 9%, 0.11%, and 45%, respectively. The packet drop rate at varying mobility speed in the presence of one gray hole and two gray hole nodes are obtained as 13% and 14% in RSDA scheme.

Healthcare institutions require advanced technology to collect patients' data accurately and continuously. The tradition technologies still suffer from two problems: performance and security efficiency. The existing research has serious drawbacks when using public-key mechanisms such as digital signature algorithms. In this paper, we propose Reliable and Efficient&nbsp, Integrity Scheme for Data Collection in HWSN (REISCH) to alleviate these problems by using secure and lightweight signature algorithms. The results of the performance analysis indicate that our scheme provides high efficiency in data integration between sensors and server (saves more than 24% of alive sensors compared to traditional algorithms). Additionally, we use Automated Validation of Internet Security Protocols and Applications (AVISPA) to validate the security procedures in our scheme. Security analysis results confirm that REISCH is safe against some well-known attacks.

Microarchitecture based side-channel attacks are common threats nowadays. Intel SGX technology provides a strong isolation from an adversarial OS, however, does not guarantee protection against side-channel attacks. In this paper, we analyze the security of the mbedTLS binary GCD algorithm, an implementation that offers interesting challenges when compared for example with OpenSSL, due to the usage of very tight loops in the former. Using practical experiments we demonstrate the mbedTLS binary GCD implementation is vulnerable to side-channel analysis using the SGX-Step framework against mbedTLS based SGX enclaves. We analyze the security of some use cases of this algorithm in this library, resulting in the discovery of a new vulnerability in the ECDSA code path that allows a single-trace attack against this implementation. This vulnerability is three-fold interesting: • It resides in the implementation of a countermeasure which makes it more dangerous due to the false state of security the countermeasure currently offers. • It reduces mbedTLS ECDSA security to an integer factorization problem. • An unexpected GCD call inside the ECDSA code path compromises the countermeasure. We also cover an orthogonal use case, this time inside the mbedTLS RSA code path during the computation of a CRT parameter when loading a private key. The attack also exploits the binary GCD implementation threat, showing how a single vulnerable primitive leads to multiple vulnerabilities. We demonstrate both security threats with end-to-end attacks using 1000 trials each, showing in both cases single-trace attacks can be achieved with success rates very close to 100%., IACR Transactions on Cryptographic Hardware and Embedded Systems, Volume 2020, Issue 2

Access control has become problematic in several organizations because of the difficulty in establishing security and preventing malicious users from mimicking roles. Moreover, there is no flexibility among users in the participation in their roles, and even controlling them. Several role-based access control (RBAC) mechanisms have been proposed to alleviate these problems, but the security has not been fully realized. In this work, however, we present an RBAC model based on blockchain technology to enhance user authentication before knowledge is accessed and utilized in a knowledge management system (KMS). Our blockchain-based system model and the smart contract ensure that transparency and knowledge resource immutability are achieved. We also present smart contract algorithms and discussions about the model. As an essential part of RBAC model applied to KMS environment, trust is ensured in the network. Evaluation results show that our system is efficient.

Instant messaging (IM) systems can be considered the most frequently used applications in mobile social networks. Nowadays, people are becoming increasingly concerned about data security and privacy protection with IM applications. Therefore, a comprehensive enhanced secure IM scheme was proposed in this paper, which is based on the elliptic curve cryptosystem and the advanced encryption standard algorithm. An offline key agreement process between users was designed under the computational Diffie-Hellman (CDH) assumption by updating the ephemeral key periodically. The proposed scheme supports denial of replaying attack and denial of forgery attack by utilizing timestamps and the elliptic curve digital signature algorithm. It supports multiple types of messages (such as document and multimedia messages) and prevents privacy leakage by storing sent and received messages with ciphertext. We proved the security of the proposed scheme under the elliptic curve discrete logarithm assumption and the CDH assumption. The comparison results of the proposed scheme with other schemes and the results of an experiment show that it is a comprehensive secure scheme with high security and good practicability.practicability.

In past years, cryptography has been considered a difficult task to achieve on sensor nodes for the Internet of Energy (IoE) owing to the resource-constrained nature of 8- and 16-bit microcontroller units (MCUs). Previous attempts at implementing cryptographic services on wireless sensor nodes have resulted in high power consumptions, long operating times, and the depletion of memory resources. Over the last decade, however, processors for the IoT and IoE have improved; with increased operating power and memory resources, longer data bus widths and low-power consumption. With the improvements made to processors suitable for building IoT devices, the question remains whether endpoint nodes should still be considered capable of only supporting the most lightweight of cryptographic mechanisms. We evaluate the capabilities of a device family (Cortex-M series processors) commonly found in programmable logic controllers to implement standard, verified software cryptographic libraries in terms of execution times, memory occupation, and power consumption in order to determine their adequacy for use in smart grid applications. It was seen that the MCUs were easily capable of running standard cryptographic algorithms. However, the use of public key cryptography may still require the inclusion of a hardware crypto accelerator or the use of a secure MCU implementing public key cryptography; as the relatively long execution times seen during the operation of ECDSA, for example, could be intolerable within a real time IoE application.

An experimental test of robustness to timing attack is reported for the widely used public-key cryptographic algorithm in IoT transducers, the Elliptic Curve Digital Signature Algorithm (ECDSA). To this aim, a timing-lattice attack is addressed on ECDSA of the firmware Library MbedTLS for ARM microcontrollers. Timing is assessed by measuring the execution time of ecdsa_write_signature of MbedTLS library implemented on an ARM Cortex-M4 microcontroller. The time intervals required to sign the messages, the messages themselves, and the signatures, are used to mount a lattice attack in order to discover ECDSA private key. Experimental results highlight the security of ECDSA function in MbedTLS library to the implemented attack.

Even though the idea of transforming basic objects to smart objects with the aid sensors is not new, it is only now that we have started seeing the incredible impact of this digital transformation in our societies. There is no doubt that the Internet of Things (IoT) has the power to change our world and drive us to a complete social evolution. This is something that has been well understood by the research and industrial communities that have been investing significant resources in the field of IoT. In business and industry, there are thousands of IoT use cases and real-life IoT deployments across a variety of sectors (e.g. industry 4.0 and smart factories, smart cities, etc.). However, due to the vastly resource-constrained nature of the devices used in IoT, implementing secure and privacy-preserving services, using, for example, standard asymmetric cryptographic algorithms, has been a real challenge. The majority of IoT devices on the market currently employ the use of various forms of symmetric cryptography such as key pre-distribution. The overall efficiency of such implementations correlates directly to the size of the IoT environment and the deployment method. In this paper, we implement a lightweight cryptographic library that can be used to secure communication protocols between multiple communicating nodes without the need for external trusted entities or a server. Our work focuses on extending the functionalities of the User Datagram Protocol (UDP) broadcast application on the Contiki-NG Operating System (OS) platform. publishedVersion

Emerging Cooperative Intelligent Transportation Systems (C-ITS) enable improved driving experience and safety guarantees, but require secure Vehicular Ad-hoc NETworks (VANETs) that must comply to strict performance constraints. Specialized standards have been defined to these aims, such as the IEEE 1609.2 that uses network-efficient cryptographic protocols to reduce communication latencies. The reduced latencies are achieved through a combination of the Elliptic Curve Qu-Vantstone (ECQV) implicit certificate scheme and the Elliptic Curve Digital Signature Algorithm (ECDSA), to guarantee data integrity and authenticity. However, literature lacks implementations and evaluations for vehicular systems. In this paper, we consider the IEEE 1609.2 standard for secure VANETs and investigate the feasibility of ECQV and ECDSA schemes when deployed in C-ITSs. We propose a prototype implementation of the standard ECQV scheme to evaluate its performance on automotive-grade hardware. To the best of our knowledge, this is the first open implementation of the scheme for constrained devices that are characterized by low computational power and low memory. We evaluate its performance against C-ITS communication latency constraints and show that, although even highly constrained devices can support the standard, complying with stricter requirements demands for higher computational resources.

Cloud computing usage has been highly increased in past decades, and this has many features to effectively store, organize and process the data. The major concern in the cloud is that security is low and user requires verification process for the data integrity. Third Party Auditing (TPA) technique is applied to verify the integrity of data and various methods has been proposed in TPA for effective performance. The existing methods in TPA has the lower performance in communication overhead and execution time. In this research, Elliptic Curve Digital Signature (ECDS) is proposed to increase the efficiency of the TPA. Bilinear mapping technique is used for verification process without retrieving the data and this helps to reduce the communication overhead. The performance of ECDA is measured and compared with the existing method to analyze the performance.

International audience; Digital Signature Algorithm (DSA) (resp. ECDSA) involves modular exponentiation (resp. scalar multiplication) of a public and known base by a random one-time exponent. In order to speed-up this operation, well-known methods take advantage of the memorization of base powers (resp. base multiples). Best approaches are the Fixed-base Radix-R method and the Fixed-base Comb method. In this paper we present a new approach for storage/online computation trade-off, by using a multiplicative splitting of the digits of the exponent radix-R representation. We adapt classical algorithms for modular exponentiation and scalar multiplication in order to take advantage of the proposed exponent recoding. An analysis of the complexity for practical size shows that our proposed approach involves a lower storage for a given level of online computation. This is confirmed by implementation results showing significant memory saving, up to 3 times for the largest NIST standardized key sizes, compared to the state of the art approaches.