Stabletrust for Private Agentic Finance

Private payments for AI agents. One key. Zero traces.

Stabletrust enables AI agents to transact privately on EVM chains - shield tokens, transfer confidentially, withdraw silently. Balances are encrypted on-chain. No one can see what your agent holds or where it sends.

Built for the private agent economy.

---

Quickstart

No SDK. No setup. Just POST.

// Shield tokens into a confidential account
await fetch("https://stabletrust-api.fairblock.network/deposit", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    privateKey: process.env.AGENT_KEY,
    tokenAddress: "0x036CbD53842c5426634e7929541eC2318f3dCF7e", // USDC
    amount: "10000000", // 10 USDC
    chainId: 84532, // Base Sepolia
  }),
});

That's it. Your agent now has a private balance no one can read.

---

Agent Flow

EOA → [account/create] → Confidential Account → [deposit]  → shielded balance
                                              → [transfer] → Recipient
Recipient → [apply] → spendable → [withdraw] → EOA

1. Create account - provision a confidential account (idempotent). Required before an account can receive a transfer.
2. Deposit - shield ERC-20 tokens. Balance becomes encrypted on-chain.
3. Transfer - send privately to any address. Amount is invisible on-chain.
4. Apply - a recipient applies received funds, moving them from pending to available so they can be spent or withdrawn.
5. Withdraw - unshield back to public ERC-20 at any time.
6. Balance - check any account's decrypted balance. Read-only - sends no transaction.

---

API

POST /account/create

Provision your confidential account (idempotent). Required before an account can receive a transfer.

const res = await fetch("https://stabletrust-api.fairblock.network/account/create", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    privateKey: process.env.AGENT_KEY,
    chainId: 84532,
  }),
});

const { address, created } = await res.json();
// { success: true, address: '0x...', created: true }  // created:false if it already existed

POST /deposit

const res = await fetch("https://stabletrust-api.fairblock.network/deposit", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    privateKey: process.env.AGENT_KEY,
    tokenAddress: "0x036CbD53842c5426634e7929541eC2318f3dCF7e",
    amount: "10000000",
    chainId: 84532,
  }),
});

const { receipt } = await res.json();
// { hash: '0x...' }

POST /balance

Read-only - decrypts and returns the balance without sending any transaction. Returns exists: false with zero balances if the account hasn't been created yet.

const res = await fetch("https://stabletrust-api.fairblock.network/balance", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    privateKey: process.env.AGENT_KEY,
    tokenAddress: "0x036CbD53842c5426634e7929541eC2318f3dCF7e",
    chainId: 84532,
  }),
});

const { exists, balance } = await res.json();
// { exists: true, balance: { total: '10000000', available: '10000000', pending: '0' } }

POST /transfer

const res = await fetch("https://stabletrust-api.fairblock.network/transfer", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    privateKey: process.env.AGENT_KEY,
    recipientAddress: "0x...recipient",
    tokenAddress: "0x036CbD53842c5426634e7929541eC2318f3dCF7e",
    amount: "5000000", // 5 USDC
    chainId: 84532,
  }),
});

const { receipt } = await res.json();
// { hash: '0x...' }

POST /apply

Apply received funds - moves a recipient's balance from pending to available so it can be spent or withdrawn.

const res = await fetch("https://stabletrust-api.fairblock.network/apply", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    privateKey: process.env.AGENT_KEY,
    chainId: 84532,
  }),
});

const { tx } = await res.json();
// { success: true, message: 'Pending balance applied', tx: '0x...' }

POST /withdraw

const res = await fetch("https://stabletrust-api.fairblock.network/withdraw", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    privateKey: process.env.AGENT_KEY,
    tokenAddress: "0x036CbD53842c5426634e7929541eC2318f3dCF7e",
    amount: "5000000",
    chainId: 84532,
  }),
});

const { receipt } = await res.json();
// { hash: '0x...' }

---

Parameters

/deposit

Field	Type	Required	Description
privateKey	string	yes	Agent wallet private key
tokenAddress	string	yes	ERC-20 token contract address
amount	string	yes	Amount in token base units
chainId	number	yes	Target network chain ID
waitForFinalization	boolean	no	Wait for tx finality (default: true)

/balance

Field	Type	Required	Description
privateKey	string	yes	Agent wallet private key (used for decryption)
tokenAddress	string	yes	ERC-20 token contract address
chainId	number	yes	Target network chain ID
address	string	no	Address to query - defaults to wallet from privateKey

/transfer

Field	Type	Required	Description
privateKey	string	yes	Agent wallet private key
recipientAddress	string	yes	Recipient Ethereum address
tokenAddress	string	yes	ERC-20 token contract address
amount	string	yes	Amount in token base units
chainId	number	yes	Target network chain ID
useOffchainVerify	boolean	no	Off-chain proof verification (default: false)
waitForFinalization	boolean	no	Wait for tx finality (default: true)

/withdraw

Field	Type	Required	Description
privateKey	string	yes	Agent wallet private key
tokenAddress	string	yes	ERC-20 token contract address
amount	string	yes	Amount in token base units
chainId	number	yes	Target network chain ID
useOffchainVerify	boolean	no	Off-chain proof verification (default: false)
waitForFinalization	boolean	no	Wait for tx finality (default: true)

/account/create

Field	Type	Required	Description
privateKey	string	yes	Agent wallet private key
chainId	number	yes	Target network chain ID
waitForFinalization	boolean	no	Wait for account finality (default: true)

/apply

Field	Type	Required	Description
privateKey	string	yes	Agent wallet private key
chainId	number	yes	Target network chain ID
waitForFinalization	boolean	no	Wait for tx finality (default: true)

---

Token Amounts and Decimals

Every amount is a string in the token's smallest unit, not in whole tokens. USDC and USDT use 6 decimals on all supported chains, so 1000000 = 1 USDC.

You want to send	Pass amount
0.01 USDC	"10000"
0.1 USDC	"100000"
1 USDC	"1000000"
10 USDC	"10000000"

The same units apply to DEPOSIT_AMOUNT, TRANSFER_AMOUNT and WITHDRAW_AMOUNT in .env (DEPOSIT_AMOUNT=2000000 deposits 2 USDC) and to the balances /balance returns ("930000" = 0.93 USDC).

Confidential balances keep 2 decimal places, so the smallest amount is 0.01 ("10000" for USDC). Finer amounts are rounded down to the cent, and anything under 0.01 is rejected.

For another token, check its decimals() and convert with ethers: ethers.parseUnits("2.5", 6).toString() returns "2500000".

---

Supported Chains

Chain	ID	Type
Arbitrum One	42161	mainnet
Base	8453	mainnet
Ethereum	1	mainnet
Base Sepolia	84532	testnet
Ethereum Sepolia	11155111	testnet
Arbitrum Sepolia	421614	testnet
Arc	5042002	testnet
Stable	2201	testnet

Arbitrum One, Base and Ethereum are mainnets. Confidential transfers and withdrawals charge a small native-ETH protocol fee (~0.00004 ETH per transfer, ~0.00002 ETH per withdrawal) in addition to gas. Withdrawals also deduct 0.001% of the amount withdrawn.

---

Running locally

npm install
cp .env.example .env   # optional: override PORT or RPC URLs
npm run dev            # http://localhost:3000, restarts on file changes

npm start runs the server without the file watcher. To try the full flow against a running server, set the demo variables in .env and run npm run demo (or npm run demo:arc for Arc).

Environment overrides:

• PORT: port to listen on (default 3000)
• RPC_URL_<chainId>: RPC endpoint for a chain, for example RPC_URL_84532
• CONTRACT_ADDRESS_<chainId>: Stabletrust contract for a chain that isn't built into the SDK (for example a local devnet)