Sending a Transaction with Encrypted Inputs

This guide assumes you have already deployed the Counter.sol contract. If you haven't already, check out our guide for deploying a Basic Private Smart Contract.

Now that we have acquired our AES encryption key, we can use it to encrypt the arguments for calling the add function of our Counter.sol contract.

TypeScript (Server)

Setup

npm install @coti-io/coti-ethers

Code

import { Contract, CotiNetwork, getDefaultProvider, Wallet } from "@coti-io/coti-ethers"

const PRIVATE_KEY = "<EOA_PRIVATE_KEY>"
const AES_KEY = "<AES_KEY>"
const COUNTER_ADDRESS = "<COUNTER_ADDRESS>"
const COUNTER_ABI = [
    {
        "inputs": [],
        "stateMutability": "nonpayable",
        "type": "constructor"
    },
    {
        "inputs": [
            {
                "components": [
                    {
                        "internalType": "ctUint64",
                        "name": "ciphertext",
                        "type": "uint256"
                    },
                    {
                        "internalType": "bytes",
                        "name": "signature",
                        "type": "bytes"
                    }
                ],
                "internalType": "struct itUint64",
                "name": "value",
                "type": "tuple"
            }
        ],
        "name": "add",
        "outputs": [],
        "stateMutability": "nonpayable",
        "type": "function"
    },
    {
        "inputs": [],
        "name": "sum",
        "outputs": [
            {
                "internalType": "ctUint64",
                "name": "",
                "type": "uint256"
            }
        ],
        "stateMutability": "view",
        "type": "function"
    }
]

const provider = getDefaultProvider(CotiNetwork.Testnet)
const wallet = new Wallet(PRIVATE_KEY, provider)
wallet.setAesKey(AES_KEY)

const counter = new Contract(COUNTER_ADDRESS, COUNTER_ABI, wallet)

const itValue = await wallet.encryptValue(
    123n,
    COUNTER_ADDRESS,
    counter.add.fragment.selector
)

await (
    await counter.add(itValue)
).wait()

TypeScript (Browser)

Setup

npm install @coti-io/coti-ethers

Code

import { BrowserProvider, Contract, Eip1193Provider, JsonRpcSigner } from '@coti-io/coti-ethers'

const AES_KEY = "<AES_KEY>"
const COUNTER_ADDRESS = "<COUNTER_ADDRESS>"
const COUNTER_ABI = [
    {
        "inputs": [],
        "stateMutability": "nonpayable",
        "type": "constructor"
    },
    {
        "inputs": [
            {
                "components": [
                    {
                        "internalType": "ctUint64",
                        "name": "ciphertext",
                        "type": "uint256"
                    },
                    {
                        "internalType": "bytes",
                        "name": "signature",
                        "type": "bytes"
                    }
                ],
                "internalType": "struct itUint64",
                "name": "value",
                "type": "tuple"
            }
        ],
        "name": "add",
        "outputs": [],
        "stateMutability": "nonpayable",
        "type": "function"
    },
    {
        "inputs": [],
        "name": "sum",
        "outputs": [
            {
                "internalType": "ctUint64",
                "name": "",
                "type": "uint256"
            }
        ],
        "stateMutability": "view",
        "type": "function"
    }
]

const provider = new BrowserProvider(window.ethereum as Eip1193Provider)
const signer = await provider.getSigner()
signer.setAesKey(AES_KEY)

const counter = new Contract(COUNTER_ADDRESS, COUNTER_ABI, signer)

const itValue = await signer.encryptValue(
    BigInt(123),
    COUNTER_ADDRESS,
    counter.add.fragment.selector
)

await (
    await counter.add(itValue)
).wait()

Python

Setup

pip install coti-web3

Code

from eth_account import Account
from eth_account.signers.local import LocalAccount
from web3 import Web3
from web3.utils.coti import (
  CotiNetwork,
  init_web3
)

PRIVATE_KEY = "<EOA_PRIVATE_KEY>"
AES_KEY = "<AES_KEY>"
COUNTER_ADDRESS = "<COUNTER_ADDRESS>"
COUNTER_ABI = [
    {
        "inputs": [],
        "stateMutability": "nonpayable",
        "type": "constructor"
    },
    {
        "inputs": [
            {
                "components": [
                    {
                        "internalType": "ctUint64",
                        "name": "ciphertext",
                        "type": "uint256"
                    },
                    {
                        "internalType": "bytes",
                        "name": "signature",
                        "type": "bytes"
                    }
                ],
                "internalType": "struct itUint64",
                "name": "value",
                "type": "tuple"
            }
        ],
        "name": "add",
        "outputs": [],
        "stateMutability": "nonpayable",
        "type": "function"
    },
    {
        "inputs": [],
        "name": "sum",
        "outputs": [
            {
                "internalType": "ctUint64",
                "name": "",
                "type": "uint256"
            }
        ],
        "stateMutability": "view",
        "type": "function"
    }
]

account: LocalAccount = Account.from_key(PRIVATE_KEY, { 'aes_key': AES_KEY })
w3: Web3 = init_web3(CotiNetwork.TESTNET)

counter_contract = w3.eth.contract(address=COUNTER_ADDRESS, abi=COUNTER_ABI)

it_value = account.encrypt_value(
    123,
    counter_contract.address,
    counter_contract.functions.add(value=(0, bytes(65))).selector
)

tx = counter_contract.functions.add(it_value).build_transaction({
    'from': account.address,
    'chainId': w3.eth.chain_id,
    'nonce': w3.eth.get_transaction_count(account.address),
    'gas': 15000000,
    'gasPrice': w3.to_wei(30, 'gwei')
})

signed_tx = w3.eth.account.sign_transaction(tx, PRIVATE_KEY)

tx_hash = w3.eth.send_raw_transaction(signed_tx.raw_transaction)

w3.eth.wait_for_transaction_receipt(tx_hash)