okx_dev_api_signing.ex

  def okx_signing(config, %{url: url, body: body, method: method}) do
    secret = config["okx_secret_key"]
    access_key = "your access key"

    timestamp = DateTime.utc_now() |> DateTime.truncate(:millisecond) |> DateTime.to_iso8601()
    %{path: path, query: query} = URI.new!(url)

    data = timestamp <> method <> path <> "?" <> query <> body
    sign = :crypto.mac(:hmac, :sha256, secret, data) |> Base.encode64()

    [
      {"OK-ACCESS-KEY", access_key},
      {"OK-ACCESS-TIMESTAMP", timestamp},
      {"OK-ACCESS-PASSPHRASE", "your passphrase"},
      {"OK-ACCESS-SIGN", sign}
    ]
  end