# anonymous-credit-tokens.info

> Experimental anonymous credit token service. Two issuers, classical ("act")
> and post-quantum ("pq"), share one JSON API; issuance is metered by proof of
> work. Status: experimental and unaudited; credits have no monetary value and may be erased at any time. Current key epoch: e1.

An anonymous credit token is a bearer credential: a server issues N credits,
the client spends them in increments with zero-knowledge proofs, and the
server cannot link spends to issuances or to each other, while a one-time
nullifier per token prevents double spending. Identical retries of issue and
spend requests replay the stored response (flagged "replayed": true); a
different request on a consumed nullifier or challenge is a final error.

## API (JSON over HTTPS, base https://anonymous-credit-tokens.info)

- GET /api/v1/{act|pq}/params: epoch, public key, limits, status line
- POST /api/v1/{act|pq}/challenge {"credits": n}: mint a single-use
  proof-of-work challenge; n clamped to 1..=1024; difficulty 18 bits at 1
  credit plus one bit per doubling; expires in 900 s
- POST /api/v1/{act|pq}/issue {"challenge_id", "nonce", "request"}: redeem
  mined work plus a scheme-native issuance request for a token
- POST /api/v1/{act|pq}/spend {"request", "requested_return"} (pq also
  requires "settlement" and "input_kind", each "direct" or "deferred"):
  spend with change
- GET /api/v1/{act|pq}/nullifier/{64-hex}: {"spent": bool}
- GET /api/v1/stats: {"act_nullifiers", "pq_nullifiers", "challenges_consumed"}
- Errors: JSON {"code", "message"}; codes: bad_request, pow_invalid,
  challenge_gone, challenge_mismatch, double_spend, proof_invalid,
  rate_limited, too_large, internal
- Body caps: 16 KB on act routes, 256 KB on pq routes; rate limits apply
- MCP (read-only): https://anonymous-credit-tokens.info/mcp with tools
  get_params, check_nullifier, get_stats

## Docs

- [How it works](https://anonymous-credit-tokens.info/how-it-works): issuance,
  spend with change, refundation, double-spend prevention
- [Failure semantics](https://anonymous-credit-tokens.info/failure-semantics):
  the retry/replay contract for dropped connections
- [API reference](https://anonymous-credit-tokens.info/api): exact envelopes,
  mining preimage, curl examples
- [Post-quantum issuer](https://anonymous-credit-tokens.info/pq): vole-act
  costs and maturity
- [Security and privacy](https://anonymous-credit-tokens.info/security)
- [Wallet](https://anonymous-credit-tokens.info/wallet)
- [Use cases](https://anonymous-credit-tokens.info/use-cases)

## Source

- [Classical scheme](https://github.com/SamuelSchlesinger/anonymous-credit-tokens)
- [Post-quantum scheme](https://github.com/SamuelSchlesinger/vole-act)