Fully-Featured Anonymous Credentials with Reputation System

Bemmann, Kai; Blömer, Johannes; Bobolz, Jan; Bröcher, Henrik; Diemert, Denis; Eidens, Fabian; Eilers, Lukas; Haltermann, Jan; Juhnke, Jakob; Otour, Burhan; Porzenheim, Laurens; Pukrop, Simon; Schilling, Erik; Schlichtig, Michael; Stienemeier, Marcel

doi:10.1145/3230833.3234517

Cited by 14 publications

(16 citation statements)

References 18 publications

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“…Recently, a group of researchers presented their implementation of an AABC system called CLARC [32]. The library implements a series of ZKP schemes but lacks a communication layer.…”

Section: Existing Implementationsmentioning

confidence: 99%

emmy – Trust-Enhancing Authentication Library

Stopar

Bizjak

Modic

et al. 2019

IFIP Advances in Information and Communication Technology

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People, organizations, devices need to make many kinds of claims as part of their everyday activities. Digital credentials can enable to transmit instantly verifiable claims about their name, date of birth, gender, location, accomplishments. Some privacy-enhancing digital credentials enable revealing only part of your identity and thus hiding all information that is not necessarily needed for the online service. In the past two decades, several privacy-and trust-enhancing authentication techniques and approaches have been proposed to implement such verifiable digital credentials, mostly on the theoretical level. Some implementations exist, but either lack functionalities, rely on heavy computational machinery or are not available in open source. This paper presents emmy, a fully-fledged open source cryptographic library for secure, privacy-aware, and trust-enhancing authentication towards online services.

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“…Recently, a group of researchers presented their implementation of an AABC system called CLARC [32]. The library implements a series of ZKP schemes but lacks a communication layer.…”

Section: Existing Implementationsmentioning

confidence: 99%

emmy – Trust-Enhancing Authentication Library

Stopar

Bizjak

Modic

et al. 2019

IFIP Advances in Information and Communication Technology

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show abstract

“…v = 5. Suppose, Alice has a reputation score scr = (n 1 , n 2 , n 3 , n 4 , n 5 , t) = (9,2,11,30,328,6940) where t = 6940 is the number of days elapsed from 1 Jan 2000 to 1 Jan 2019. Alice can prove the following statements about her score:…”

Section: Performance Analysismentioning

confidence: 99%

“…Each user uses a pseudonym for reporting readings within a certain period and transfers the gained score to the next pseudonym when the next time period starts while preventing attackers from linking these pseudonyms. Reputation systems proposed in [9][10][11] allow each user to anonymously rate a product at most once. If a user rates the same product multiple times, his anonymity will be broken because these ratings are linkable.…”

Section: Other Related Workmentioning

confidence: 99%

“…If a user rates the same product multiple times, his anonymity will be broken because these ratings are linkable. The system in [11] is based on group signatures with linkability while the scheme in [9] combines anonymous credentials with a reputation system. These systems focus on protecting anonymity for the rater but not for the ratee and they do not consider how to manage and protect reputation scores.…”

Section: Other Related Workmentioning

confidence: 99%

“…Various privacy-preserving reputation schemes [5,6,[9][10][11]15,[20][21][22] (see also Section 7 for more discussion) have been proposed to protect anonymity of raters and ratees to some extent, but none of these aims to hide reputation scores against the reputation manager. As far as we know, only [27,30,36] discuss the protection of reputation scores.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

pRate: Anonymous Star Rating with Rating Secrecy

Liu

Manulis

2019

Applied Cryptography and Network Security

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We introduce pRate, a novel reputation management scheme with strong security and privacy guarantees for the users and their reputation scores. The reputation scores are computed based on the (aggregated) number(s) of stars that users receive from their raters. pRate allows users to advertise privacy-friendly statements about their reputation when searching for potential transaction partners. Ratings can only be submitted by partners who have been initially authorised by the ratee and issued a rating token. The scheme is managed by a possibly untrusted reputation manager who can register users and assist ratees in updating their reputation scores, yet without learning these scores. In addition to ensuring the secrecy of the ratings, a distinctive feature of pRate over prior proposals, is that it hides the identities of raters and ratees from each other during the transaction and rating stages. The scheme is built from a number of efficient cryptographic primitives; its security is formally modeled and proven to hold under widely used assumptions on bilinear groups.

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MoniPoly—An Expressive q-SDH-Based Anonymous Attribute-Based Credential System

Tan

Groß

2020

Advances in Cryptology – ASIACRYPT 2020

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Modern attribute-based anonymous credential (ABC) systems benefit from special encodings that yield expressive and highly efficient show proofs on logical statements. The technique was first proposed by Camenisch and Groß, who constructed an SRSA-based ABC system with prime-encoded attributes that offers efficient AND, OR and NOT proofs. While other ABC frameworks have adopted constructions in the same vein, the Camenisch-Groß ABC has been the most expressive and asymptotically most efficient proof system to date, even if it was constrained by the requirement of a trusted message-space setup and an inherent restriction to finite-set attributes encoded as primes. In this paper, combining a new set commitment scheme and an SDH-based signature scheme, we present a provably secure ABC system that supports show proofs for complex statements. This construction is not only more expressive than existing approaches, but it is also highly efficient under unrestricted attribute space due to its ECC protocols only requiring a constant number of bilinear pairings by the verifier; none by the prover. Furthermore, we introduce strong security models for impersonation and unlinkability under adaptive active and concurrent attacks to allow for the expressiveness of our ABC as well as for a systematic comparison to existing schemes. Given this foundation, we are the first to comprehensively formally prove the security of an ABC with expressive show proofs. Specifically, building upon the the q-(co-)SDH assumption, we prove the security against impersonation with a tight reduction. Besides the set commitment scheme, which may be of independent interest, our security models can serve as a foundation for the design of future ABC systems.

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Fully-Featured Anonymous Credentials with Reputation System

Cited by 14 publications

References 18 publications

emmy – Trust-Enhancing Authentication Library

emmy – Trust-Enhancing Authentication Library

pRate: Anonymous Star Rating with Rating Secrecy

MoniPoly—An Expressive q-SDH-Based Anonymous Attribute-Based Credential System

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