Security Analysis of the Unrestricted Identity-Based Aggregate Signature Scheme

Aggregate signatures allow anyone to combine different signatures signed by different signers on different messages into a single short signature. An ideal aggregate signature scheme is an identity-based aggregate signature (IBAS) scheme that supports full aggregation since it can reduce the total transmitted data by using an identity string as a public key and anyone can freely aggregate different signatures. Constructing a secure IBAS scheme that supports full aggregation in bilinear maps is an important open problem. Recently, Yuan {\it et al.} proposed an IBAS scheme with full aggregation in bilinear maps and claimed its security in the random oracle model under the computational Diffie-Hellman assumption. In this paper, we show that there exists an efficient forgery attacker on their IBAS scheme and their security proof has a serious flaw.Comment: 9 page

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筑波大学 (University of Tsukuba)201

APEX2S: A Two-Layer Machine Learning Model for Discovery of host-pathogen protein-protein Interactions on Cloud-based Multiomics Data

Presented by the avalanche of biological interactions data, computational biology is now facing greater challenges on big data analysis and solicits more studies to mine and integrate cloud-based multiomics data, especially when the data are related to infectious diseases. Meanwhile, machine learning techniques have recently succeeded in different computational biology tasks. In this article, we have calibrated the focus for host-pathogen protein-protein interactions study, aiming to apply the machine learning techniques for learning the interactions data and making predictions. A comprehensive and practical workflow to harness different cloud-based multiomics data is discussed. In particular, a novel two-layer machine learning model, namely APEX2S, is proposed for discovery of the protein-protein interactions data. The results show that our model can better learn and predict from the accumulated host-pathogen protein-protein interactions

Aggregatable Certificateless Designated Verifier Signature

In recent years, the Internet of Things (IoT) devices have become increasingly deployed in many industries and generated a large amount of data that needs to be processed in a timely and efficient manner. Using aggregate signatures, it provides a secure and efficient way to handle large numbers of digital signatures with the same message. Recently, the privacy issue has been concerned about the topic of data sharing on the cloud. To provide the integrity, authenticity, authority, and privacy on the data sharing in the cloud storage, the notion of an aggregatable certificateless designated verifier signature scheme (ACLDVS) was proposed. ACLDVS also is a perfect tool to enable efficient privacy-preserving authentication systems for IoT and or the vehicular ad hoc networks (VANET). Our concrete scheme was proved to be secured underling of the Computational Diffie-Hellman assumption. Compared to other related schemes, our scheme is efficient, and the signature size is considerably short

Revisiting the security model for aggregate signature schemes

Aggregate signature schemes combine the digital signatures of multiple users on different messages into one single signature. The Boneh-Gentry-Lynn-Shacham (BGLS) aggregate signature scheme is one such scheme, based on pairings, where anyone can aggregate the signatures in any order. We suggest improvements to its current chosen-key security model. In particular, we argue that the scheme should be resistant to attackers that can adaptively choose their target users, and either replace other users' public keys or expose other users' private keys. We compare these new types of forgers to the original targeted-user forger, building up to the stronger replacement-and-exposure forger. Finally, we present a security reduction for a variant of the BGLS aggregate signature scheme with respect to this new notion of forgery. Recent attacks by Joux and others on the discrete logarithm problem in small-characteristic finite fields dramatically reduced the security of many type I pairings. Therefore, we explore security reductions for BGLS with type III rather than type I pairings. Although our reductions are specific to BGLS, we believe that other aggregate signature schemes could benefit from similar changes to their security models

Cryptanalysis of an online/offline certificateless signature scheme for Internet of Health Things

Recently, Khan et al. [An online-offline certificateless signature scheme for internet of health things,” Journal of Healthcare Engineering, vol. 2020] presented a new certificateless offline/online signature scheme for Internet of Health Things (IoHT) to fulfill the authenticity requirements of the resource-constrained environment of (IoHT) devices. The authors claimed that the newly proposed scheme is formally secured against Type-I adversary under the Random Oracle Model (ROM). Unfortunately, their scheme is insecure against adaptive chosen message attacks. It is demonstrated that an adversary can forge a valid signature on a message by replacing the public key. Furthermore, we performed a comparative analysis of the selective parameters including computation time, communication overhead, security, and formal proof by employing Evaluation based on Distance from Average Solution (EDAS). The analysis shows that the designed scheme of Khan et al. doesn’t have any sort of advantage over the previous schemes. Though, the authors utilized a lightweight hyperelliptic curve cryptosystem with a smaller key size of 80-bits. Finally, we give some suggestions on the construction of a concrete security scheme under ROM

Research on a New Signature Scheme on Blockchain

With the rise of Bitcoin, blockchain which is the core technology of Bitcoin has received increasing attention. Privacy preserving and performance on blockchain are two research points in academia and business, but there are still some unresolved issues in both respects. An aggregate signature scheme is a digital signature that supports making signatures on many different messages generated by many different users. Using aggregate signature, the size of the signature could be shortened by compressing multiple signatures into a single signature. In this paper, a new signature scheme for transactions on blockchain based on the aggregate signature was proposed. It was worth noting that elliptic curve discrete logarithm problem and bilinear maps played major roles in our signature scheme. And the security properties of our signature scheme were proved. In our signature scheme, the amount will be hidden especially in the transactions which contain multiple inputs and outputs. Additionally, the size of the signature on transaction is constant regardless of the number of inputs and outputs that the transaction contains, which can improve the performance of signature. Finally, we gave an application scenario for our signature scheme which aims to achieve the transactions of big data on blockchain

A unified framework for trapdoor-permutation-based sequential aggregate signatures

We give a framework for trapdoor-permutation-based sequential aggregate signatures (SAS) that unifies and simplifies prior work and leads to new results. The framework is based on ideal ciphers over large domains, which have recently been shown to be realizable in the random oracle model. The basic idea is to replace the random oracle in the full-domain-hash signature scheme with an ideal cipher. Each signer in sequence applies the ideal cipher, keyed by the message, to the output of the previous signer, and then inverts the trapdoor permutation on the result. We obtain different variants of the scheme by varying additional keying material in the ideal cipher and making different assumptions on the trapdoor permutation. In particular, we obtain the first scheme with lazy verification and signature size independent of the number of signers that does not rely on bilinear pairings. Since existing proofs that ideal ciphers over large domains can be realized in the random oracle model are lossy, our schemes do not currently permit practical instantiation parameters at a reasonable security level, and thus we view our contribution as mainly conceptual. However, we are optimistic tighter proofs will be found, at least in our specific application.https://eprint.iacr.org/2018/070.pdfAccepted manuscrip

Improvements and New Constructions of Digital Signatures

Ein digitales Signaturverfahren, oft auch nur digitale Signatur genannt, ist ein wichtiger und nicht mehr wegzudenkender Baustein in der Kryptographie. Es stellt das digitale Äquivalent zur klassischen handschriftlichen Signatur dar und liefert darüber hinaus noch weitere wünschenswerte Eigenschaften. Mit solch einem Verfahren kann man einen öffentlichen und einen geheimen Schlüssel erzeugen. Der geheime Schlüssel dient zur Erstellung von Signaturen zu beliebigen Nachrichten. Diese können mit Hilfe des öffentlichen Schlüssels von jedem überprüft und somit verifiziert werden. Desweiteren fordert man, dass das Verfahren "sicher" sein soll. Dazu gibt es in der Literatur viele verschiedene Begriffe und Definitionen, je nachdem welche konkreten Vorstellungen beziehungsweise Anwendungsgebiete man hat. Vereinfacht gesagt, sollte es für einen Angreifer ohne Kenntnis des geheimen Schlüssels nicht möglich sein eine gültige Signatur zu einer beliebigen Nachricht zu fälschen. Ein sicheres Signaturverfahren kann somit verwendet werden um die folgenden Ziele zu realisieren: - Authentizität: Jeder Empfänger kann überprüfen, ob die Nachricht von einem bestimmten Absender kommt. - Integrität der Nachricht: Jeder Empfänger kann feststellen, ob die Nachricht bei der Übertragung verändert wurde. - Nicht-Abstreitbarkeit: Der Absender kann nicht abstreiten die Signatur erstellt zu haben. Damit ist der Einsatz von digitalen Signaturen für viele Anwendungen in der Praxis sehr wichtig. Überall da, wo es wichtig ist die Authentizität und Integrität einer Nachricht sicherzustellen, wie beim elektronischen Zahlungsverkehr, Softwareupdates oder digitalen Zertifikaten im Internet, kommen digitale Signaturen zum Einsatz. Aber auch für die kryptographische Theorie sind digitale Signaturen ein unverzichtbares Hilfsmittel. Sie ermöglichen zum Beispiel die Konstruktion von stark sicheren Verschlüsselungsverfahren. Eigener Beitrag: Wie bereits erwähnt gibt es unterschiedliche Sicherheitsbegriffe im Rahmen von digitalen Signaturen. Ein Standardbegriff von Sicherheit, der eine recht starke Form von Sicherheit beschreibt, wird in dieser Arbeit näher betrachtet. Die Konstruktion von Verfahren, die diese Form der Sicherheit erfüllen, ist ein vielschichtiges Forschungsthema. Dazu existieren unterschiedliche Strategien in unterschiedlichen Modellen. In dieser Arbeit konzentrieren wir uns daher auf folgende Punkte. - Ausgehend von vergleichsweise realistischen Annahmen konstruieren wir ein stark sicheres Signaturverfahren im sogenannten Standardmodell, welches das realistischste Modell für Sicherheitsbeweise darstellt. Unser Verfahren ist das bis dahin effizienteste Verfahren in seiner Kategorie. Es erstellt sehr kurze Signaturen und verwendet kurze Schlüssel, beides unverzichtbar für die Praxis. - Wir verbessern die Qualität eines Sicherheitsbeweises von einem verwandten Baustein, der identitätsbasierten Verschlüsselung. Dies hat unter anderem Auswirkung auf dessen Effizienz bezüglich der empfohlenen Schlüssellängen für den sicheren Einsatz in der Praxis. Da jedes identitätsbasierte Verschlüsselungsverfahren generisch in ein digitales Signaturverfahren umgewandelt werden kann ist dies auch im Kontext digitaler Signaturen interessant. - Wir betrachten Varianten von digitalen Signaturen mit zusätzlichen Eigenschaften, sogenannte aggregierbare Signaturverfahren. Diese ermöglichen es mehrere Signaturen effizient zu einer zusammenzufassen und dabei trotzdem alle zugehörigen verschiedenen Nachrichten zu verifizieren. Wir geben eine neue Konstruktion von solch einem aggregierbaren Signaturverfahren an, bei der das Verfahren eine Liste aller korrekt signierten Nachrichten in einer aggregierten Signatur ausgibt anstatt, wie bisher üblich, nur gültig oder ungültig. Wenn eine aggregierte Signatur aus vielen Einzelsignaturen besteht wird somit das erneute Berechnen und eventuell erneute Senden hinfällig und dadurch der Aufwand erheblich reduziert