Trust at Infrastructure Scale: Cryptographic Architecture and Resilience Engineering for the EU Digital Identity Wallet

Abstract

Background: eIDAS 2.0 (Regulation (EU) 2024/1183, in force 20 May 2024) obliges every member state to offer citizens a European Digital Identity Wallet (EUDI Wallet) by the end of 2026. The regulatory build-out ran on schedule through 2025: five implementing regulations on core functionalities and interfaces (December 2024), and seven further trust-services regulations plus an electronic-attestations regulation (July 2025) — the largest deployment of verifiable-credential infrastructure ever attempted. Objective: We analyze the wallet's cryptographic architecture and its resilience-engineering requirements: what must hold for a credential infrastructure at the scale of 450 million residents to be trustworthy, and which failure classes its design must survive. Methods: Documentary analysis of the regulation, the implementing regulations, and the underlying open standards (W3C Verifiable Credentials 2.0, ISO/IEC 18013-5 mobile driving licence, SD-JWT-class selective disclosure); construction of an ecosystem architecture model; and a risk-versus-mechanism coverage assessment. Results: The wallet's trust model distributes cryptographic authority across issuers, holders, and registered relying parties — an architectural inversion of centralized identity that removes the standing honeypot but creates a new resilience surface: revocation latency, verifier over-collection, certification gaps between wallet solutions, and cross-border interoperability failures. The 2025 implementing regulations address the governance layer (trust services, attestations) but leave the operational-resilience layer — revocation infrastructure guarantees, ecosystem-scale incident response — as open engineering work. Conclusions: Digital identity at infrastructure scale is the decade's most consequential trust build; its security will be decided less by cryptography (which is largely settled) than by operational resilience engineering — revocation with guarantees, recovery with rehearsals, transparency for components that fail silently, and the humility to keep manual fallbacks while the ecosystem itself is the newest and least-tested component.