K Khay Elixir SDK 💧

Official Elixir and Phoenix SDK for K Khay — The Non-Custodial Crypto Payment Gateway

Accept non-custodial cryptocurrency payments across 190+ blockchain networks and 500+ tokens (EVM, Bitcoin, Solana, TON, Tron, and XRPL) with zero custody and automatic direct-to-wallet settlement in Phoenix web applications and distributed Elixir OTP nodes.

Gateway Dashboard • API Keys • Website

⚡ Highlights

• 🛡️ 100% Non-Custodial: Payments settle directly to your destination blockchain address in seconds. K Khay never holds your private keys or customer funds.
• 🌐 190+ Networks Supported:
  • EVM Networks (180+ Chains): BNB Smart Chain (bsc), Polygon (polygon), Base (base), Arbitrum (arbitrum), Ethereum (ethereum), Optimism (optimism), Avalanche (avalanche).
  • UTXO Chains: Bitcoin (bitcoin), Dogecoin (dogecoin), Litecoin (litecoin), Bitcoin Cash (bitcoincash).
  • High-Throughput Chains: Solana (solana), TON (ton), Tron (tron), XRP Ledger (ripple).
• 🪙 500+ Tokens: Native coins and tokens (USDT, USDC, BTC, ETH, SOL, TON, BNB, DOGE, XRP, TRX, LTC, DAI, and more).
• 🔗 Branded Hosted Checkouts: Automatic payment links with dynamic QR codes, live blockchain polling, and wallet deep linking.
• 🔔 HMAC-SHA256 Cryptographic Webhooks: Timing-safe verification matching x-kkhay-signature.
• ⚡ Zero Native Dependencies: Uses Erlang's built-in :httpc and :crypto modules with JSON decoding.

📦 Installation

Add kkhay to your list of dependencies in mix.exs:

def deps do
  [
    {:kkhay, "~> 1.0.4"}
  ]
end

Then run:

mix deps.get

🚀 Quick Start

1. Initialize the Client

Generate your API key in the K Khay Gateway Dashboard.

client = Kkhay.client(System.get_env("KKHAY_API_KEY"))

2. Create a Crypto Payment Invoice

Accept stablecoins, native coins, or let the customer choose their chain on checkout:

# Example: USDT on BNB Smart Chain (BSC)
{:ok, response} =
  Kkhay.create_invoice(client, %{
    amount: 49.99,
    currency: "USD",
    pay_network: "bsc",       # "bsc" | "polygon" | "base" | "arbitrum" | "ethereum" | "solana" | "bitcoin" | "ton"
    pay_token: "USDT",        # "USDT" | "USDC" | "BTC" | "ETH" | "SOL" | "TON"
    order_id: "ORDER-7711",   # Your internal order ID
    title: "Pro Subscription",
    customer_email: "elixirdev@example.com",
    redirect_url: "https://myshop.com/success"
  })

invoice = response["invoice"]
IO.puts("Invoice ID: #{invoice["id"]}")
IO.puts("Gateway ID: #{invoice["gatewayId"]}")
IO.puts("Deposit Address: #{invoice["depositAddress"]}")
IO.puts("Checkout Hosted URL: #{invoice["hostedUrl"]}")

# Redirect customer to the hosted checkout:
# Phoenix.Controller.redirect(conn, external: invoice["hostedUrl"])

# Example: Native Bitcoin or Solana
{:ok, btc_res} =
  Kkhay.create_invoice(client, %{
    amount: 120.00,
    currency: "USD",
    pay_network: "bitcoin",
    pay_token: "BTC",
    order_id: "ORDER-7712"
  })

3. Fetch & List Invoices

# Retrieve a single invoice with blockchain transaction history
{:ok, res} = Kkhay.get_invoice(client, "01940000-0000-7000-8000-000000000001")
invoice = res["invoice"]
payments = res["payments"]

IO.puts("Status: #{invoice["status"]}") # WAITING | PAID | EXPIRED | CANCELED

# List invoices with pagination
{:ok, list} = Kkhay.list_invoices(client, %{status: "PAID", limit: 10})
IO.puts("Total Paid Invoices: #{list["totalCount"]}")

4. Verify Incoming Webhooks (Phoenix Controller)

When a customer pays and the blockchain confirms the transaction, K Khay sends a cryptographically signed POST webhook to your server:

defmodule MyAppWeb.KkhayWebhookController do
  use MyAppWeb, :controller
  alias Kkhay.Webhook

  def handle(conn, _params) do
    {:ok, raw_body, conn} = Plug.Conn.read_body(conn)
    signature = Plug.Conn.get_req_header(conn, "x-kkhay-signature") |> List.first()
    secret = System.get_env("KKHAY_WEBHOOK_SECRET")

    case Webhook.parse_event(raw_body, signature, secret) do
      {:ok, event} ->
        if event["event"] == "payment.paid" do
          # Fulfill customer order in database
          MyApp.Orders.complete_order(event["order_id"], event["tx_hash"])
        end

        json(conn, %{ok: true})

      {:error, _reason} ->
        conn
        |> put_status(:unauthorized)
        |> json(%{error: "Invalid webhook signature"})
    end
  end
end

🌐 Supported Networks & Families

📄 License

MIT © K Khay