Participatory digital humanities challenge traditional authorship by making research a co-created and socially accountable process. Yet, as participation increasingly relies on complex digital infrastructures, including platforms, algorithms, and AI-driven tools, the ethical foundations of trust, authorship, and accountability remain fragile. This paper asks a fundamental question: who owns participation when knowledge is co-produced across institutions, communities, and automated systems?

Grounded in the CARE principles (Collective Benefit, Authority to Control, Responsibility, Ethics), this contribution argues that ethical and sustainable participatory research requires a rethinking of infrastructure itself, not merely as technical support, but as a moral and relational framework. The paper explores the potential of blockchain as infrastructure of care: socio-technical systems designed to sustain transparency, and accountability in participatory digital humanities.

Rather than presenting blockchain as a tool for efficiency or automation, the paper conceptualizes it as a mechanism of relational accountability. In contrast to existing mechanisms for authorship attribution, such as Persistent Identifiers (PIDs), which primarily ensure identification and linkage, and may prove insufficient in capturing the dynamic, distributed, and multi-agent nature of participatory knowledge production, blockchain-based systems enable the distributed certification of contributions, the traceability of collaborative processes, and the verification of evolving authorship relations across heterogeneous agents. In participatory research contexts, particularly those involving community partners, citizen humanities, and public-facing digital archives, blockchain-based certification can provide verifiable attribution of authorship, provenance, and contribution histories without relying solely on centralized institutional authority. This certification is understood not as proprietary ownership, but as protective recognition: a way to acknowledge and safeguard diverse intellectual and cultural contributions while allowing knowledge to circulate openly. A possible application of this approach can be envisioned in collaborative digital archives, where contributions from researchers, community members, and AI systems are recorded, validated, and made transparently traceable over time.

The relevance of such infrastructures becomes even more pronounced in an AI-mediated research ecosystem. As AI systems participate in content generation, annotation, classification, and interpretation, traditional notions of authorship and responsibility are further destabilized. The paper argues that blockchain-based infrastructures can function as counter-infrastructures to AI opacity, making visible the human, collective, and situated labor that automated systems often obscure. Blockchain and AI are not competing technologies, but interacting layers within a broader knowledge ecology that demands explicit ethical governance.

Adopting a critical perspective, the paper also interrogates the environmental, social, and political costs of blockchain infrastructures. Drawing on critical infrastructure studies and public digital humanities scholarship, it proposes criteria for CARE-aligned infrastructures: low-energy architectures, transparent and participatory governance models, accessibility beyond technical elites, and long-term stewardship commitments. These criteria aim to ensure that trust infrastructures do not reproduce existing inequalities or extractive practices under the guise of innovation. From a feasibility perspective, such infrastructures can be envisioned as incremental and interoperable layers built upon existing digital research ecosystems, enabling gradual adoption across communities and institutions rather than requiring immediate large-scale transformation.

Ultimately, this paper contends that trust is not a neutral by-product of technology, but a value that must be deliberately designed, negotiated, and maintained.