ExkPasswd is a highly optimized password generation and analysis library for Elixir.

This library provides secure, customizable password generation based on the XKPasswd concept - creating memorable yet strong passwords by combining random words with numbers, symbols, and various transformations.

Quick Start

# Generate a password with default settings
ExkPasswd.generate()
#=> "28?heavy?SOUND?later?94"

# Use a preset
ExkPasswd.generate(:xkcd)
#=> "correct-horse-battery-staple-amazing"

# Custom configuration using keyword list
ExkPasswd.generate(num_words: 4, separator: "-")
#=> "12-Happy-Forest-Dance-56"

# Custom configuration using Config struct
config = ExkPasswd.Config.new!(
  num_words: 4,
  separator: "-",
  case_transform: :capitalize
)
ExkPasswd.generate(config)
#=> "12-Happy-Forest-Dance-56"

# Analyze password strength
password = ExkPasswd.generate()
ExkPasswd.analyze_strength(password, ExkPasswd.Config.new!())
#=> %{rating: :good, entropy_bits: 59.2, ...}

# Generate multiple passwords in batch
ExkPasswd.generate_batch(100)
#=> ["password1", "password2", ...]

Features

• Efficient generation: Constant-time word selection using tuple indexing
• Entropy calculation: Security analysis with blind and seen entropy metrics
• Character substitutions: Leetspeak-style transformations for added complexity
• Custom dictionaries: Load your own word lists for any language or domain
• Batch generation: Optimized for generating multiple passwords
• Strength analysis: Password feedback and improvement suggestions
• Extensibility: Transform protocol for custom password transformations
• Zero dependencies: Only uses Elixir stdlib and :crypto

Performance

• Tuple-based lookups: Constant-time word selection
• Cached transformations: Pre-computed case variants
• Buffered random generation: Reduced syscalls for batch operations

Available Presets

• :default - Balanced security and memorability (~59 bits entropy)
• :web32 - For websites allowing up to 32 characters (~65 bits)
• :web16 - For websites with 16 character limit (~42 bits - ⚠️ low security)
• :wifi - 63 character WPA2 keys (~85 bits)
• :apple_id - Meets Apple ID requirements (~55 bits)
• :security - For security questions (~77 bits)
• :xkcd - Similar to the famous XKCD comic (~65 bits)

See ExkPasswd.Config.Presets for more details on each preset.

Extensibility

Custom transforms can be added using the Transform protocol.

Example: Japanese Romaji Transform for cross-keyboard compatibility:

defmodule MyApp.RomajiTransform do
  @moduledoc """
  Converts Japanese hiragana/katakana to romaji for keyboard portability.

  Enables passwords created on Japanese keyboard layouts to be typed on
  English QWERTY keyboards (e.g., international travel, shared workstations).
  """
  defstruct [:mode]

  @hiragana_to_romaji %{
    "あ" => "a", "い" => "i", "う" => "u", "さ" => "sa", "き" => "ki"
  }

  defimpl ExkPasswd.Transform do
    def apply(%{mode: _mode}, word, _config) do
      @hiragana_to_romaji
      |> Enum.reduce(word, fn {japanese, romaji}, acc ->
        String.replace(acc, japanese, romaji)
      end)
    end

    def entropy_bits(%{mode: _mode}, _config), do: 0.0
  end
end

# Use with Japanese dictionary
ExkPasswd.Dictionary.load_custom(:japanese, ["さくら", "やま", "うみ"])

config = ExkPasswd.Config.new!(
  num_words: 2,
  dictionary: :japanese,
  meta: %{
    transforms: [%MyApp.RomajiTransform{mode: :hiragana}]
  }
)

ExkPasswd.generate(config)
#=> "45-sakura-yama-89"  # Typeable on any keyboard