Web Crypto API PBKDF2 Generate Password

by Anish

Posted on Monday september 17, 2018

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This sample chapter extracted from the book, Cryptography for JavaScript Developers.

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Here's an example showing how to use deriveKey() to create a Secure Remote Password (also known as Proof of Secret) from a user's password using pbkdf2 algorithm

The PBKDF2 Demo

Input Iteration in Numbers:
Provide Password:

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PBKDF2 Derived Key (Hex):
Random Salt (Hex) :
Note: Using Fixed salt will generate the same derive key

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The Web crypto api Javascript example PBKDF

function generateKey(password,iterations) {
    // salt should be Uint8Array or ArrayBuffer

    var saltBuffer = crypto.getRandomValues(new Uint8Array(8));
    var encoder = new TextEncoder('utf-8');
    var passphraseKey = encoder.encode("password");

    // You should firstly import your passphrase Uint8array into a CryptoKey
window.crypto.subtle.importKey(
  'raw', 
  passphraseKey, 
  {name: 'PBKDF2'}, 
  false, 
  ['deriveBits', 'deriveKey']
).then(function(key) {

  return window.crypto.subtle.deriveKey(
    { "name": 'PBKDF2',
      "salt": saltBuffer,
      // don't get too ambitious, or at least remember
      // that low-power phones will access your app
      "iterations": iterations,
      "hash": 'SHA-256'
    },
    key,

    // Note: for this demo we don't actually need a cipher suite,
    // but the api requires that it must be specified.
    // For AES the length required to be 128 or 256 bits (not bytes)
    { "name": 'AES-CBC', "length": 256 },

    // Whether or not the key is extractable (less secure) or not (more secure)
    // when false, the key can only be passed as a web crypto object, not inspected
    true,

    // this web crypto object will only be allowed for these functions
    [ "encrypt", "decrypt" ]
  )
}).then(function (webKey) {

  return crypto.subtle.exportKey("raw", webKey);

}).then(function (buffer) {

     document.getElementById("key").value= bytesToHexString(buffer);
     document.getElementById("salt").value= bytesToHexString(saltBuffer);
});

}

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Download the sample code here

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Next Reading Perform AES Encryption Using importKey Method

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