Mint cAROUSD

Convert public test stablecoin into encrypted cAROUSD and step onto the confidential rail.

Minting converts public stablecoin into cAROUSD at 1:1; after a mint, value that used to be visible on-chain becomes an encrypted balance. Minting requires a custodial wallet: the sandbox signs the on-chain calls with the wallet’s key.

Prerequisites

• A custodial wallet with ETH for gas (faucet covers this).
• In backed mode, the wallet must also hold enough public stablecoin to deposit. In float mode the operator mints directly, so a stablecoin balance in your wallet is not required. See mint modes.

Make the call

curl -s "$BASE/mint" \
  -H "Authorization: Bearer $KEY" \
  -H "content-type: application/json" \
  -d "{\"walletId\":\"$WALLET\",\"amount\":\"100\"}"

{
  "ok": true,
  "data": {
    "transaction": {
      "id": "cktxn0002…",
      "type": "MINT",
      "status": "CONFIRMED",
      "amount": "100.00",
      "token": "cAROUSD",
      "txHash": "0x51b7…",
      "explorerUrl": "https://sepolia.etherscan.io/tx/0x51b7…",
      "walletId": "ckwlt0001…",
      "createdAt": "2026-08-13T09:40:00.000Z",
      "updatedAt": "2026-08-13T09:40:52.000Z"
    }
  }
}

amount is a required decimal string in human units. The call blocks up to ~90 seconds for the receipt; if it returns PENDING, poll GET /transactions/{id} until terminal.

What happens on-chain

Backed mode

1. Your wallet approves the commitment contract to spend the stablecoin.
2. The wallet calls commitDeposit: stablecoin is locked in the commitment, and the equivalent cAROUSD is minted to the wallet as an encrypted amount.

Every cAROUSD in circulation is collateralized by stablecoin held in the contract.

Float mode

The operator calls confidentialMint for your wallet with the encrypted amount. Your stablecoin balance is untouched; the operator’s float backs redemptions instead.

Either way, the encryption of the minted amount happens server-side: you send "100", the sandbox produces the FHE ciphertext and proof.

Verify

curl -s "$BASE/balances?walletId=$WALLET" -H "Authorization: Bearer $KEY" \
  | jq '.data.balances[0] | {normal: .normal.amount, confidential: .confidential.amount}'

In backed mode you’ll see normal decrease and confidential increase by the minted amount; in float mode only confidential moves.

Common failures

Response	Meaning
400 validation	Missing/invalid amount, unknown wallet, external wallet, or insufficient stablecoin (backed mode).
502 mint_failed	The on-chain call reverted. In float mode this usually means the operator is missing ROLE_MINTER; in backed mode, the stablecoin may not be allow-listed on the commitment. Platform-side; see Troubleshooting.

The first confidential operation after a deployment restart fetches FHE keys and can be noticeably slower. Don’t tune timeouts to that first call.

Next: send a private transfer or redeem back to stablecoin.