The current shift towards digital transactions emphasizes the need for robust Qualified Electronic Signature (QES) frameworks that safeguard integrity and privacy. Having the potential to become the leading type of adopted QES, the main challenge that Remote QESs present to end users is choosing between transmitting the entire document or only its digest to the Trust Service Provider (TSP). The first option compromises the document’s confidentiality, while the second one requires the development of signature applications compliant with advanced signature formats, a task that often needs additional time and resources. In this paper, we introduce a comprehensive strategy for remote QESs, designed for seamless integration with current client applications, while simultaneously maintaining user privacy. The main topics approached in this paper are the following: a comprehensive architecture for privacy-aware remote QES systems, relevant standards and legislation, integration scenarios for clients, and remote QES standard protocols to assure communication between client and TSP environments. Furthermore, we also explore the integration of our proposed solution with an enhanced long-term preservation service that uses Ethereum smart contracts and methodologies to implement signature applications with advanced electronic signatures via open-source libraries while ensuring document privacy. The main result of this work is a flexible on-premise module that provides the ability to sign, validate, and preserve documents, with a minimal integration effort.

The use of Verifiable Credentials under the new eIDAS Regulation introduces privacy concerns, particularly during revocation status checks. This paper proposes a privacy-preserving revocation mechanism tailored to the European Digital Identity Wallet and its Architecture and Reference Framework. Our method publishes a daily randomized revocation list as a cascaded Bloom filter, enhancing unlinkability by randomizing revocation indexes derived from ARF guidelines. The implementation extends open-source components developed by the European Committee. This work demonstrates a practical, privacy-centric approach to revocation in digital identity systems, supporting the advancement of privacy-preserving technologies.

This paper presents a comprehensive review of existing research on the integration of blockchain technologies with the trust service ecosystem governed by the Electronic Identification, Authentication and Trust Services (eIDAS) Regulation of the European Union (EU). While Public Key Infrastructure (PKI) and electronic signature (ES) systems deployed under eIDAS provide strong cryptographic guarantees, standardized protocols, and cross-border legal recognition, their operational model remains largely centralized, concentrating trust in supervised authorities and service providers. This centralization raises concerns related to transparency, auditability, and resilience that blockchain, with its decentralized consensus and immutable distributed ledgers, has been increasingly explored to address. This review covers the most relevant application domains in which blockchain has been proposed as a complementary layer for Trust Service Providers (TSPs): certificate lifecycle management, remote signature services, signature preservation, signature validation, timestamping, content provenance and authenticity, and the European digital identity (EUDI) Wallet ecosystem. For each domain, this paper analyzes how blockchain can strengthen auditability and distributed trust while preserving the interoperability, legal assurance, and standards compliance required by eIDAS and ETSI (European Telecommunications Standards Institute) frameworks. A quantitative comparison of latency, throughput, and operational costs between blockchain-augmented and traditional architectures is provided, together with a technology maturity classification for each application domain. Finally, the paper identifies current limitations, including scalability, regulatory alignment, privacy constraints, and the absence of production-scale pilot data, and outlines open research challenges for the adoption of blockchain in regulated digital trust services.