1,720,970 research outputs found
Making Classical (Threshold) Signatures Post-quantum for Single Use on a Public Ledger
No full textThe Bitcoin architecture heavily relies on the ECDSA signature scheme which is broken by quantum adversaries as the secret key can be computed from the public key in quantum polynomial time. To mitigate this attack, bitcoins can be paid to the hash of a public key (P2PKH). However, the first payment reveals the public key so all bitcoins attached to it must be spent at the same time (i.e. the remaining amount must be transferred to a new wallet). Some problems remain with this approach: the owners are vulnerable against rushing adversaries between the time the signature is made public and the time it is committed to the blockchain. Additionally, there is no equivalent mechanism for threshold signatures. Finally, no formal analysis of P2PKH has been done. In this paper, we formalize the security notion of a digital signature with a hidden public key and we propose and prove the security of a generic transformation that converts a classical signature to a post-quantum one that can be used only once. We compare it with P2PKH. Namely, our proposal relies on pre-image resistance instead of collision resistance as for P2PKH, so allows for shorter hashes. Additionally, we propose the notion of a delay signature to address the problem of the rushing adversary when used with a public ledger and discuss the advantages and disadvantages of our approach. We further extend our results to threshold signatures.LASE
Extractable Witness Encryption for the Homogeneous Linear Equations Problem
No full textWitness encryption is a cryptographic primitive which encrypts a message under an instance of an NP language and decrypts the ciphertext using a witness associated with that instance. In the current state of the art, most of the witness encryption constructions are based on multilinear maps. Following the construction of Choi and Vaudenay based on RSA-related problems, we suggest a novel witness key encapsulation mechanism based on the hardness of solving homogeneous linear Diophantine equations (HLE problem). Our arithmetic-based construction aims to solve an issue raised by these authors where the security might be compromised if the adversary is able to find small solutions to a homogeneous linear Diophantine equation, while avoiding the inefficiency of multilinear maps. The security of our scheme is based on a hidden group order and a knowledge assumption.LASE
Count Me In! Extendability for Threshold Ring Signatures
Get PDFRing signatures enable a signer to sign a message on behalf of a group anonymously, without revealing her identity. Similarly, threshold ring signatures allow several signers to sign the same message on behalf of a group; while the combined signature reveals that some threshold t of the group members signed the message, it does not leak anything else about the signers’ identities. Anonymity is a central feature in threshold ring signature applications, such as whistleblowing, e-voting and privacy-preserving cryptocurrencies: it is often crucial for signers to remain anonymous even from their fellow signers. When the generation of a signature requires interaction, this is difficult to achieve. There exist threshold ring signatures with non-interactive signing—where signers locally produce partial signatures which can then be aggregated—but a limitation of existing threshold ring signature constructions is that all of the signers must agree on the group on whose behalf they are signing, which implicitly assumes some coordination amongst them. The need to agree on a group before generating a signature also prevents others—from outside that group—from endorsing a message by adding their signature to the statement post-factum. We overcome this limitation by introducing extendability for ring signatures, same-message linkable ring signatures, and threshold ring signatures. Extendability allows an untrusted third party to take a signature, and extend it by enlarging the anonymity set to a larger set. In the extendable threshold ring signature, two signatures on the same message which have been extended to the same anonymity set can then be combined into one signature with a higher threshold. This enhances signers’ anonymity, and enables new signers to anonymously support a statement already made by others. For each of those primitives, we formalize the syntax and provide a meaningful security model which includes different flavors of anonymous extendability. In addition, we present concrete realizations of each primitive and formally prove their security relying on signatures of knowledge and the hardness of the discrete logarithm problem. We also describe a generic transformation to obtain extendable threshold ring signatures from same-message-linkable extendable ring signatures. Finally, we implement and benchmark our constructions
Post-quantum Asynchronous Deniable Key Exchange and the Signal Handshake
Get PDFISSN:0302-9743ISSN:1611-3349ISSN:1611-334
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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