Supply chain traceability ledger

The challenge

A minerals importer had to prove ethical sourcing to buyers, but custody evidence lived in PDFs from five different suppliers.

What we did

• Designed smart contracts recording custody transfers and certifications.
• Built a web app so suppliers log events without touching a wallet.
• Stored supporting documents with content-addressed hashes on IPFS.
• Produced buyer-facing verification pages per batch.

The outcome

• Verifiable chain of custody across five supplier tiers.
• Buyer due-diligence requests answered with a link, not a document hunt.
• Certification expiry tracked and enforced automatically.

Stack

• Solidity
• Polygon
• Node.js
• React
• IPFS