Blacksheep: regulated fiat ↔ crypto payments API (AU/NZ)

Blacksheep is a regulated stablecoin / multicurrency payments product (Australia AUSTRAC + New Zealand FSP) with a public API so you can quote, swap, and withdraw between fiat and crypto programmatically — bank rails on one side, self-custody wallets on the other.

Product: blacksheep.money. Docs: docs.blacksheep.money/docs. App: my.blacksheep.money. API base: https://api.blacksheep.money. X: @Blacksheepmoney.

Related: crypto cards · Solana neobank how-to · RedotPay.

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What the API is for

Docs pitch: move money between fiat and crypto programmatically — manage external bank and wallet destinations, and receive webhooks for state changes. Marketing emphasizes local rails (e.g. NPP for AUD, ACH for USD), direct bank ↔ wallet paths, and keeping a model where users can maintain custody of funds outside the platform when withdrawing to wallets.

This is a regulated payments / FX API, not a Solana DEX aggregator. Solana shows up as a wallet address family (sol) for crypto withdrawals when the asset/chain pair supports it.

Domain model

Transaction types and states

Prefer webhooks over polling. No client idempotency key on mutations — a retry is a new transaction; guard duplicates on your side.

HTTP shape

Money encoding

Amounts are never floats. Wire format:

{
  "value": "1500000",
  "code": "USDC",
  "decimals": 6,
  "chain": "ethereum"
}

value is a string-encoded integer in the smallest unit; crypto also carries chain. Responses may add a metadata string field. Use BigInt / decimal libs — not Number.

Authentication (Ed25519)

No bearer tokens. Dashboard (Settings → Dev space) creates an Ed25519 keypair in-browser, registers the public key, and shows once:

Signing string joins length-prefixed fields with : (length first prevents delimiter injection):

{len(keyId)}:{keyId}:{len(ts)}:{ts}:{len(nonce)}:{nonce}:{METHOD}:{len(path)}:{path}:{Content-Digest}

Docs ship a Node.js signRequest helper. First call example: POST https://api.blacksheep.money/v1/account.balance.getMany. Use standard base64 (not base64url) for nonce, signature, and digest.

Core flows

Swap

quote.get → (show user) → transaction.initiateSwap
         → webhook transaction.updated (COMPLETED | FAILED | …)

// POST /quote.get — currency_out.value "0" means "price the output"
{
  "currency_in":  { "value": "100000000", "code": "USDC", "decimals": 6, "chain": "ethereum" },
  "currency_out": { "value": "0", "code": "AUD", "decimals": 2 }
}

// POST /transaction.initiateSwap — both sides non-zero; out from quote ask
{
  "currency_in":  { "value": "100000000", "code": "USDC", "decimals": 6, "chain": "ethereum" },
  "currency_out": { "value": "154700", "code": "AUD", "decimals": 2 },
  "external_accounts": { "from": null, "to": null }
}
// → { "data": "<transaction-uuid>" }

Refresh quotes every 5–10s on a confirmation UI. Engine validates implied rate vs market then re-quotes at execution. Native crypto↔crypto direct pairs are rejected — bridge via USDC/USDT. Minimum sizes and unsupported codes return BAD_REQUEST.

Withdraw to bank or wallet

Register external accounts once; withdraw with transaction.submitWithdraw + external_account_id. Wallet list: account.external.web3.getAll. Wallet metadata.type is one of:

Match wallet family to currency_out.chain. Network fees come out of the requested amount. On-chain refs appear on the transaction when available (external_reference).

Webhooks

Register HTTPS URLs in the dashboard (not via API key endpoints). Deliveries carry webhook-id, webhook-timestamp, webhook-signature (v1a,<b64>). Signature covers id.timestamp.rawBody with the webhook’s Ed25519 public key. Respond 2xx within 20s; verify, apply ~5 minute timestamp window, and dedupe on webhook-id.

Builder checklist

Resources

• Docs home · API reference · Authentication
• Guides: Swapping · Withdraw to wallet · Withdraw to bank · Webhooks
• Playground
• Blacksheep on DevRels

Bottom line

Blacksheep gives ANZ-regulated fiat rails plus a clean public API: Ed25519-signed POSTs, strict money objects, quote → swap → webhook, and withdrawals to banks or multi-family wallets including Solana. For builders shipping AUD/NZD ↔ stablecoin product paths, start at auth + balances, then swap and withdraw guides — treat live chain/asset support as dashboard/docs truth, not assumptions from this summary.