Computes the Password-Based Key Derivation Function 2.

@param {string} password
@param {string} salt
@param {number} iterations
@param {number} keySize (in bytes)
@param {string} hash - The hash name ('sha1', 'sha2-512, ...)
@returns {string} - A new password
function pbkdf2 (password, salt, iterations, keySize, hash) {
  const hasher = hashName[hash]
  if (!hasher) {
    throw new Error(`Hash '${hash}' is unknown or not supported`)
  }
  const dek = forgePbkdf2(
    password,
    salt,
    iterations,
    keySize,
    hasher)
  return forgeUtil.encode64(dek)
}