From Paper Trails to Trust on Tracks: Adding Public Transparency to Railways via zk-SNARKs

TL;DR

Trust on Tracks presents a framework to add public transparency to railway process modifications by combining attestation chains, digital signatures, and zk-SNARKs to verify process correctness off-chain while publishing compact proofs on-chain. The approach models hierarchical responsibilities and business rules, enabling verifiability without exposing sensitive details, and is instantiated for Phase 1 of Germany's Sektorleitlinie 22 to validate practicality and scalability. The work demonstrates feasible off-chain execution with on-chain proofs, analyzes performance and storage costs, and discusses generalizability to other critical-infrastructure governance contexts. Overall, it offers a privacy-preserving, scalable pathway to public accountability in regulated processes without mandating full on-chain process migration.

Abstract

Railways provide a critical service and operate under strict regulatory frameworks for implementing changes or upgrades. Despite their impact on the public, these frameworks do not define means or mechanisms for transparency towards the public, leading to reduced trust and complex tracking processes. We analyse the German guideline for railway-infrastructural modifications from proposal to approval, using the guideline as a motivating example for modelling decisions in processes using digital signatures and zero-knowledge proofs. Therein, a verifier can verify that a process was executed correctly by the involved parties and according to specification without learning confidential information such as trade secrets or identities of the participants. We validate our system by applying it to the railway process, demonstrating how it realises various rules, and we evaluate its scalability with increased process complexities. Our solution is not railway-specific but also applicable to other contexts, helping leverage zero-knowledge proofs for public transparency and trust.

Figures (5)

• Figure 1: Tree structure of roles
• Figure 2: Mycorrhizal network of the requirement specification phase
• Figure 3: Tree structure of the requirement specification phase
• Figure 4: Attestation Chain Construction using Standard Signature Scheme $\mathsf{Sig}$.
• Figure 5: Preprocessing of Attestation Chains. All chains are extended with the root attestor public key $rpk$, forming a tree of attestations rooted at $rpk$.