index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Encrypt messages</title>
    <link rel="stylesheet" href="style.css" />
  </head>
  <body>
    <div id="password">
      <input type="password" id="passwordtxt" placeholder="text" />
      <button id="passwordsub" onclick="password()">Submit</button>
    </div>
    <div id="parent">
      <h1 id="hi">Input</h1>
      <input type="text" placeholder="text" id="txt" /> <br />
      <button onclick="encrypt()">Encrypt</button> <br />

      <button onclick="decrypt()">Decrypt</button> <br />
      <h1 id="hi2">Output</h1>
      <input type="text" placeholder="output" id="txt2" />
    </div>
    <script src="script.js"></script>
  </body>
</html>