IDI-Wallet: A Non-Custodial Digital Identity Wallet for Blockchain Interoperability

November 3, 2025

The digital identity landscape remains fragmented, with siloed blockchain ecosystems and incompatible credential formats limiting privacy, portability, and developer adoption. This thesis addresses that fragmentation by presenting the design and implementation of the Interoperable Digital Identity Wallet (IDI-Wallet), a local-first, non-custodial wallet that unifies credential flows through a single interface. The main contribution is a modular architecture and working system that enables users to create, store, and present verifiable credentials across heterogeneous identity platforms, advancing self-sovereign iden- tity (SSI) principles and interoperability with identity platforms and tools such as Veramo, walt.id, and Privado ID. IDI-Wallet enforces privacy by design: on-device key management, password-derived encryption at rest, minimal disclosure by default, and explicit consent dialogs. The implementation normalizes diverse protocols and formats, including W3C DIDs, Verifiable Credentials, OpenID4VCI and OpenID4VP, SD- JWT, and Zero-Knowledge Proofs. Evaluation was conducted on Ethereum, Polygon, and cheqd, validating the full lifecycle from DID creation to credential issuance, selective disclosure, proof generation, and exchange across platforms and blockchains. Results confirm functional correctness, interoperability, and alignment with key security properties of confidentiality, integrity, and availability. This work delivers a concrete prototype and a reusable blueprint for future identity systems that preserve user control and privacy while adapting to evolving standards.

Authors in the community:

• 

  V

  Vincenzo Filangeri

  ist1110837

Supervisors of this institution:

• 

  M

  Miguel Nuno Dias Alves Pupo Correia

  ist130598

• 

  A

  André Ferreira Ferrão Couto e Vasconcelos

  ist14250

electrical-engineering-electronic-engineering-information-engineering - Electrical engineering, electronic engineering, information engineering

eng - English

Instituto Superior Técnico