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Item type:Publication, Access status: without files , Routing cross-blockchain communicationBlockchain Interoperability Solutions (BISs) enable seamless communication and transactions between two or more blockchains. These solutions form an additional heterogeneous set on top of the blockchain layer and impose new constraints on cross-blockchain communication. This new interconnected network of blockchains can provide different communication routes, resulting in the need to find an optimal route between the source and target blockchains. In this paper, we aim to foster discussion about the problems and opportunities that the widescale adoption of BISs brings. We define the problem of using multiple BISs to route cross-blockchain communication and develop theoretical foundations for cross-blockchain routing. Based on the formalization, we implement and evaluate an algorithm that returns an optimal route for a communication request, given a network of blockchains and user-defined objectives.Publicationtype: Conference Paper42 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , UPPR: universal privacy-preserving revocation(IEEE, 2025-10); ; ; ; Self-Sovereign Identity (SSI) frameworks enable individuals to receive and present digital credentials in a user-controlled way. Revocation mechanisms ensure that invalid or withdrawn credentials cannot be misused. These revocation mechanisms must be scalable (e.g., at national scale) and preserve core SSI principles such as privacy, user control, and interoperability. Achieving both is hard, and finding a suitable trade-off remains a key challenge in SSI research.This paper introduces UPPR, a revocation mechanism for One-Show Verifiable Credentials (oVCs) and unlinkable Anonymous Credentials (ACs). Revocations are managed using percredential Verifiable Random Function (VRF) tokens, which are published in a Bloom filter cascade on a blockchain. Holders prove non-revocation via a VRF proof for oVCs or a single Zero-Knowledge Proof for ACs. The construction prevents revocation status tracking, allows holders to stay offline, and hides issuer revocation behavior. We analyze the privacy properties of UPPR and provide a prototype implementation on Ethereum. Our implementation enables off-chain verification at no cost. On-chain checks cost 0.56–0.84 USD, while issuers pay only 0.00002–0.00005 USD per credential to refresh the revocation state.Publicationtype: Conference Paper43 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Non-interactive threshold BBS+ from pseudorandom correlations(Springer, 2025-04); ; ; ; The BBS+ signature scheme is one of the most prominent solutions for realizing anonymous credentials. Its prominence is due to properties like selective disclosure and efficient protocols for creating and showing possession of credentials. Traditionally, a single credential issuer produces BBS+ signatures, which poses significant risks due to a single point of failure.I n this work, we address this threat via a novel t-out-of-n threshold BBS+ protocol. Our protocol supports an arbitrary security threshold t≤n and works in the so-called preprocessing setting. In this setting, we achieve non-interactive signing in the online phase and sublinear communication complexity in the number of signatures in the offline phase, which, as we show in this work, are important features from a practical point of view. As it stands today, none of the widely studied signature schemes, such as threshold ECDSA and threshold Schnorr, achieve both properties simultaneously. In this work, we make the observation that presignatures can be directly computed from pseudorandom correlations which allows servers to create signatures shares without additional cross-server communication. Both our offline and online protocols are actively secure in the Universal Composability model. Finally, we evaluate the concrete efficiency of our protocol, including an implementation of the online phase and the expansion algorithm of the pseudorandom correlation generator (PCG) used during the offline phase. The online protocol without network latency takes less than 14 ms for t≤30 and credentials sizes up to 10. Further, our results indicate that the influence of t on the online signing is insignificant, ≤6% for t≤30, and the overhead of the thresholdization occurs almost exclusively in the offline phase. Our implementation of the PCG expansion shows that even for a committee size of 10 servers, each server can expand a correlation of up to 217 presignatures in less than 100 ms per presignature.Publicationtype: Conference Paper29