Simple Password Generator

• Source code on GitHub

Introduction 

Sometimes you need to create words from a given alphabet, so I'd like to share a very simple solution. The solution is scalable, so you can add your own alphabet. Let's take a look at the code.

Using the Code

The code consists of several classes:

• AlphabetDictionaries - predefined alphabets
• AlphabetWordGenerator - generate word accordingly alphabet

public static class AlphabetDictionaries
{
    public const string EnglishLowerCase = "abcdefghijklmnopqrstuvwxyz";
    public const string EnglishUpperCase = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    public const string Numeric = "0123456789";
    public const string SpecialSymbols = "`~!@#$%^&*()-_=+[]{}\\|;:'\",<.>/?";
}   

Here's main and only one class - AlphabetWordGenerator: 

public sealed class AlphabetWordGenerator : IWordGenerator
{
    private readonly string _alphabet;
    private readonly RNGCryptoServiceProvider _provider = new RNGCryptoServiceProvider();

    public AlphabetWordGenerator(ICollection<string> alphabets)
    {
        if (alphabets == null || alphabets.Count == 0)
        {
            throw new ArgumentException("Alphabets is null or empty");
        }
        if (alphabets.Any(string.IsNullOrWhiteSpace))
        {
            throw new ArgumentException("Alphabet should not be ampty");
        }
        _alphabet = string.Join(string.Empty, alphabets);
    }

    public AlphabetWordGenerator(string alphabet)
        : this(new[] { alphabet })
    {
    }

    public string Generate(int wordLength)
    {
        if (wordLength < 1)
        {
            throw new IndexOutOfRangeException("wordLength is out of range");
        }
        return DoGenerate(wordLength);
    }

    private string DoGenerate(int wordLength)
    {
        var repository = new List<char>(wordLength);
        var data = new byte[wordLength];
        _provider.GetBytes(data);
        foreach (byte item in data)
        {
            int index = Convert.ToInt32(item)%_alphabet.Length;
            char symbol = _alphabet[index];
            repository.Add(symbol);
        }
        return string.Join(string.Empty, repository);
    }
} 

Let's create a word with lowercase English letters:

var generator = new AlphabetWordGenerator(AlphabetDictionaries.EnglishLowerCase);
                    
var password = generator.Generate(10); 

Result password is equal to uddfxjfbxp 

Another example with several alphabets:

var alphabets = new List<string>
{
    AlphabetDictionaries.EnglishLowerCase,
    AlphabetDictionaries.EnglishUpperCase,
    AlphabetDictionaries.Numeric,
    AlphabetDictionaries.SpecialSymbols,
};

var generator = new AlphabetWordGenerator(alphabets);
                    
var password = generator.Generate(40);    

Result password is equal to [3xH(kzizo@51m@q}qpIYq[CgUBbjKf^3E@JF^T;

History

• 26^th July, 2012: Initial version
• 20^th December, 2013: Length's been moved to generate method