Zero-Trust Client-Side Anchoring for Blockchain Evidence Integrity.

We introduce EVIDEX, a client-side anchoring protocol that produces tamper-evident digital evidence without trusting the server that collects it. The scheme composes cryptographic commitments across heterogeneous blockchains to guarantee integrity, provenance and verifiability under a zero-trust threat model — even in the presence of a fully-compromised aggregator.

EVIDEX is designed so that a court, a regulator or a third auditor can verify the integrity of any collected artifact using only public chain state — no cooperation from the original service is required. The paper formalizes the threat model, proves integrity under standard cryptographic assumptions and evaluates the protocol against alternative anchoring designs.