On Addressing Isolation in Blockchain-Based Self-Sovereign Identity
Andreea Elena Drăgnoiu, Andrei Ciobanu, Ruxandra F. Olimid
TL;DR
This paper addresses the isolation of blockchains as a barrier to blockchain-based Self-Sovereign Identity (SSI) interoperability. It defines cross-chain SSI scenarios based on where DIDs are anchored and where verifications occur, and it lays out security, privacy, interoperability, and data-consistency requirements to guide design. Through an analysis of cross-chain mechanisms and industry solutions, it discusses concrete use-cases such as cross-chain authentication, token airdrops, and identity merging, while highlighting challenges in revocation propagation, unlinkability, standardization, and decentralization. The work establishes a framework for developing interoperable SSI across multi-chain ecosystems and identifies open questions that motivate future research in scalability, governance, and implementation.
Abstract
Self-Sovereign Identity (SSI) grants holders full ownership and control of their digital identities, being the ultimate digital identity model. Operating in a decentralized manner, SSI enables the verification of claims, including privacy-preserving mechanisms. Blockchain, which can be used to implement a Verifiable Data Registry (VDR), is often considered one of the pillars of SSI, along with Decentralized Identifiers (DIDs) and Verifiable Credentials (VCs). Unfortunately, blockchains are mostly siloed, affecting the interoperability and universality of SSI. We investigate the effect of blockchain isolation on blockchain-based SSI. We first define possible scenarios for cross-chain SSI and exemplify with real-life use cases. We then define specific requirements for cross-chain SSI and identify challenges, also in relation to the identified scenarios. We explore various solutions to achieve blockchain interoperability, with a focus on SSI. In particular, we identify the advantages and disadvantages of distinct cross-chain models for cross-chain SSI. Finally, we address the usability of cross-chain SSI and discuss security and privacy aspects, opening the way for future research.