Structure-preserving signatures (SPS) are a powerful building block for cryptographic protocols. We introduce SPS on equivalence classes (SPS-EQ), which allow joint randomization of messages and signatures. Messages are projective equivalence classes defined on group-element vectors, so multiplying a vector by a scalar yields a different representative of the same class. Our scheme lets one adapt a signature for one representative to a signature for another representative without knowledge of any secret. Moreover, given a signature, an adapted signature for a different representative is indistinguishable from a fresh signature on a random message. We propose a definitional framework for SPS-EQ and an efficient construction in Type-3 bilinear groups, which we prove secure against generic forgers. We also introduce set-commitment schemes that let one open subsets of the committed set. From this and SPS-EQ, we then build an efficient multi-show attribute-based anonymous credential system for an arbitrary number of attributes. Our ABC system avoids costly zero-knowledge proofs and only requires a short interactive proof to thwart replay attacks. It is the first credential system whose bandwidth required for credential showing is independent of the number of its attributes, i.e., constant-size. We propose strengthened game-based security definitions for ABC and prove our scheme anonymous against malicious organizations in the standard model; finally, we discuss a concurrently secure variant in the CRS model.

/pdf/structure-preserving-signatures-on-equivalence-classes-and-255b963aw0.pdf

Structure-Preserving Signatures on Equivalence Classes and Constant-Size Anonymous Credentials

A verifiable timed signature (VTS) scheme allows one to time-lock a signature on a known message for a given amount of time T such that after performing a sequential computation for time T anyone can extract the signature from the time-lock. Verifiability ensures that anyone can publicly check if a time-lock contains a valid signature on the message without solving it first, and that the signature can be obtained by solving the same for time T. This work formalizes VTS, presents efficient constructions compatible with BLS, Schnorr, and ECDSA signatures, and experimentally demonstrates that these constructions can be employed in practice. On a technical level, we design an efficient cut-and-choose protocol based on the homomorphic time-lock puzzles to prove the validity of a signature encapsulated in a time-lock puzzle. We also present a new efficient range proof protocol that significantly improves upon existing proposals in terms of the proof size, and is also of independent interest. While VTS is a versatile tool with numerous existing applications, we demonstrate VTS's applicability to resolve three novel challenging issues in the space of cryptocurrencies. Specifically,we show how VTS is the cryptographic cornerstone to construct:(i) Payment channel networks with improved on-chain unlinkability of users involved in a transaction, (ii) multi-party signing of transactions for cryptocurrencies without any on-chain notion oftime and (iii) cryptocurrency-enabled fair multi-party computation protocol.

Verifiable Timed Signatures Made Practical

Conjunctive grammars are an extension of ordinary (“context-free”) grammars with a conjunction operator, which can be used in any rules to specify a substring that satisfies several syntactic conditions simultaneously. This family has been systematically studied since the turn of the century, and is a subject of current studies. This paper gives an overview of the current state of the art in the research on conjunctive grammars.

A Tale of Conjunctive Grammars

The Generalized LR parsing algorithm for context-free grammars is notable for having a decent worst-case running time (cubic in the length of the input string, if implemented efficiently), as well as much better performance on “good” grammars. This paper extends the Generalized LR algorithm to the case of “grammars with left contexts” (M. Barash, A. Okhotin, “An extension of context-free grammars with one-sided context specifications”, Inform. Comput., 2014), which augment the context-free grammars with special operators for referring to the left context of the current substring, along with a conjunction operator (as in conjunctive grammars) for combining syntactical conditions. All usual components of the LR algorithm, such as the parsing table, shift and reduce actions, etc., are extended to handle the context operators. The resulting algorithm is applicable to any grammar with left contexts and has the same worst-case cubic-time performance as in the case of context-free grammars.

Generalized LR Parsing Algorithm for Grammars with One-Sided Contexts

Two-sided context specifications in formal grammars

In structure-preserving signatures on equivalence classes SPS-EQ-$$\mathcal {R}$$, introduced at $$\textsc {Asiacrypt}$$ 2014, each message M in $$\mathbb {G}^*^\ell $$ is associated to its projective equivalence class, and a signature commits to the equivalence class: anybody can transfer the signature to a new, scaled, representative.

In this work, we give the first black-box construction of a public-key encryption scheme from any SPS-EQ-$$\mathcal {R}$$ satisfying a simple new property which we call perfect composition. The construction does notinvolve any non-black-box technique and the implication is that such SPS-EQ-$$\mathcal {R}$$ cannot be constructed from one-way functions in a black-box way. The main idea of our scheme is to build a verifiable encrypted signature VES first and then apply the general transformation suggested by Calderon et al. CT-RSA 2014.

The original definition of VES requires that the underlying signature scheme be correct and secure in addition to other security properties. The latter have been extended in subsequent literature, but the former requirements have sometimes been neglected, leaving a hole in the security notion. We show that Calderon et al.'s notion of resolution independence fills this gap.

/pdf/verifiably-encrypted-signatures-security-revisited-and-a-new-bw5scjq2e9.pdf

Verifiably Encrypted Signatures: Security Revisited and a New Construction

Barash and Okhotin (“Grammars with two-sided contexts”, Tech. Rep. 1090, Turku Centre for Computer Science, 2013) recently introduced conjunctive grammars with two-sided contexts, and gave a variant of Valiant’s algorithm which recognizes the languages they generate in O(|G|2·n 3.3727) time and O(|G|·n 2) space. We use a new normal form and techniques from logic programming to improve this to O(|G|·n 3), without increasing the space usage.

Recognizing Two-Sided Contexts in Cubic Time

We develop a necessary condition for ET0L languages inspired by Ogden's Lemma. Besides being useful for proving that individual languages are not ET0L languages, this result also gives an alternative proof of Ehrenfeucht and Rozenberg's theorem about rare and nonfrequent symbols in ET0L languages.

/pdf/ogden-s-lemma-for-et0l-languages-2pxbbty74a.pdf

Ogden's lemma for ET0L languages

Ogden's lemma for random permitting-and forbidding-context and ET0L languages

Generalized random context picture grammars (grcpgs) are a method of syntactic picture generation. The terminals are subsets of the Euclidean plane and the replacement of variables involves the building of functions that will eventually be applied to terminals. Context is used to permit or forbid production rules.

Generalized Random Context Picture Grammars: The State of the Art

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Max Rabkin

Author Tools

Chat about Author