Anchor transaction

The anchor transaction is the on-chain artifact that gives LearnCoin credentials their cryptographic trust anchor. When a batch of credentials is signed and Merkle-rooted, the 32-byte root is written to a Base L2 transaction — specifically, as calldata in a transaction signed by the LearnCoin anchoring key.

Each credential's proof.proofValue encodes both the Merkle path from its leaf to the root and a reference to the anchor transaction. A verifier follows the path, lands on the root, and then confirms the root is present in the declared transaction on Base. That's the final link in the trust chain.

Anchor transactions are visible on basescan.org. The verification page at /c/<id> includes a direct link. Per-credential cost scales down logarithmically: a batch of 10,000 credentials is one anchor transaction, which means about $0.0003 per credential at typical Base gas prices.