c2sp

Verifiable Usage Receipts for AI APIs. Cryptographic proof that your token bill is real. Ed25519 + Fulcio signing, RFC 6962 Merkle proofs, Trillian Tessera log, C2SP witness cosigning, Rekor public anchoring, Rust tokenizer verification. No blockchain.

Verifiable compliance evidence: hash-chained ledgers, signed tip, hybrid Ed25519+ML-DSA-65, KMS custody, evidence packs, C2SP checkpoints + tlog-witness (split-view evidence, ML-DSA-44 cosignatures, real Rekor checkpoints verified), SCITT RFC 9943; verifiers in Python, JS, Go, Rust, Java + differential oracle. AGPL-3.0 / commercial.

Reference implementation of the INK transparency witness (Auditability §7). Source for implementers to inspect. Not guaranteed to mirror our production witness at witness.tulpa.network.

A complete C2SP transparency log in one file — plus the witness, the offline proof verifier, and the tile builder. The live stack behind log.markovianprotocol.com.