Web3 DApp Integration: TON Connect, Wallet Signing & Smart Contract Calls

import hashlib
import time
from nacl.signing import VerifyKey

def verify_ton_proof(proof_data: dict, app_domain: str, server_payload: str) -> bool:
    # 1. Validate payload matches dynamic nonce issued by backend
    if proof_data['payload'] != server_payload:
        return False

    # 2. Check 15-minute TTL expiration
    timestamp = proof_data['timestamp']
    if abs(time.time() - timestamp) > 900:
        return False

    # 3. Reconstruct signed message buffer
    # buffer = 'ton-proof-item-v2/' + wc + addr_hash + domain_len + domain + timestamp + payload
    domain_bytes = app_domain.encode('utf-8')
    prefix = b"ton-proof-item-v2/"
    wc_byte = proof_data['workchain'].to_bytes(4, 'little', signed=True)
    addr_hash = bytes.fromhex(proof_data['address'])
    domain_len = len(domain_bytes).to_bytes(4, 'little')
    ts_bytes = timestamp.to_bytes(8, 'little')
    payload_bytes = server_payload.encode('utf-8')

    msg = prefix + wc_byte + addr_hash + domain_len + domain_bytes + ts_bytes + payload_bytes
    msg_hash = hashlib.sha256(msg).digest()
    full_msg_hash = hashlib.sha256(b"\xff\xff" + b"ton-connect" + msg_hash).digest()

    # 4. Verify Ed25519 signature against wallet public key
    public_key_bytes = bytes.fromhex(proof_data['public_key'])
    signature_bytes = bytes.fromhex(proof_data['signature'])

    try:
        verify_key = VerifyKey(public_key_bytes)
        verify_key.verify(full_msg_hash, signature_bytes)
        return True # Authenticated! Mint JWT session token.
    except Exception:
        return False

import { beginCell, toNano, Address } from '@ton/core';
import { tonConnectUI } from './tonConnect';

async function sendJettonPayment(jettonWallet: string, recipient: string, amountUnits: bigint) {
  // 1. Build TEP-74 Jetton transfer BOC cell
  const forwardPayload = beginCell()
    .storeUint(0, 32) // 0 means simple text comment follows
    .storeStringTail("TGWAY VIP Subscription #198")
    .endCell();

  const bodyCell = beginCell()
    .storeUint(0x0f8a7ea5, 32)           // opcode: transfer
    .storeUint(0, 64)                   // query_id
    .storeCoins(amountUnits)            // Jetton amount (e.g. 50 USDT = 50,000,000)
    .storeAddress(Address.parse(recipient)) // destination address
    .storeAddress(Address.parse(recipient)) // response_destination for excess TON
    .storeBit(0)                        // custom_payload (null)
    .storeCoins(toNano('0.02'))          // forward_ton_amount (triggers notification)
    .storeBit(1)                        // forward_payload stored as cell reference
    .storeRef(forwardPayload)
    .endCell();

  // 2. Dispatch transaction via TON Connect UI
  const tx = {
    validUntil: Math.floor(Date.now() / 1000) + 360,
    messages: [{
      address: jettonWallet,
      amount: toNano('0.05').toString(), // attached gas fee
      payload: bodyCell.toBoc().toString('base64')
    }]
  };

  const result = await tonConnectUI.sendTransaction(tx);
  console.log("Transaction BOC signed & dispatched:", result.boc);
}