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Brute force implementation / C#
class Program
#region Private variables
// the secret password which we will try to find via brute force
private static string password = "p123";
private static string result;
private static bool isMatched = false;
/* The length of the charactersToTest Array is stored in a
* additional variable to increase performance */
private static int charactersToTestLength = 0;
private static long computedKeys = 0;
/* An array containing the characters which will be used to create the brute force keys,
* if less characters are used (e.g. only lower case chars) the faster the password is matched */
private static char[] charactersToTest =
'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j',
'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
'u', 'v', 'w', 'x', 'y', 'z','A','B','C','D','E',
static void Main(string[] args)
var timeStarted = DateTime.Now;
Console.WriteLine("Start BruteForce - {0}", timeStarted.ToString());
// The length of the array is stored permanently during runtime
charactersToTestLength = charactersToTest.Length;
// The length of the password is unknown, so we have to run trough the full search space
var estimatedPasswordLength = 0;
while (!isMatched)
/* The estimated length of the password will be increased and every possible key for this
* key length will be created and compared against the password */
Console.WriteLine("Password matched. - {0}", DateTime.Now.ToString());
Console.WriteLine("Time passed: {0}s", DateTime.Now.Subtract(timeStarted).TotalSeconds);
Console.WriteLine("Resolved password: {0}", result);
Console.WriteLine("Computed keys: {0}", computedKeys);
#region Private methods
/// <summary>
/// Starts the recursive method which will create the keys via brute force
/// </summary>
/// <param name="keyLength">The length of the key</param>
private static void startBruteForce(int keyLength)
var keyChars = createCharArray(keyLength, charactersToTest[0]);
// The index of the last character will be stored for slight perfomance improvement
var indexOfLastChar = keyLength - 1;
createNewKey(0, keyChars, keyLength, indexOfLastChar);
/// <summary>
/// Creates a new char array of a specific length filled with the defaultChar
/// </summary>
/// <param name="length">The length of the array</param>
/// <param name="defaultChar">The char with whom the array will be filled</param>
/// <returns></returns>
private static char[] createCharArray(int length, char defaultChar)
return (from c in new char[length] select defaultChar).ToArray();
/// <summary>
/// This is the main workhorse, it creates new keys and compares them to the password until the password
/// is matched or all keys of the current key length have been checked
/// </summary>
/// <param name="currentCharPosition">The position of the char which is replaced by new characters currently</param>
/// <param name="keyChars">The current key represented as char array</param>
/// <param name="keyLength">The length of the key</param>
/// <param name="indexOfLastChar">The index of the last character of the key</param>
private static void createNewKey(int currentCharPosition, char[] keyChars, int keyLength, int indexOfLastChar)
var nextCharPosition = currentCharPosition + 1;
// We are looping trough the full length of our charactersToTest array
for (int i = 0; i < charactersToTestLength; i++)
/* The character at the currentCharPosition will be replaced by a
* new character from the charactersToTest array => a new key combination will be created */
keyChars[currentCharPosition] = charactersToTest[i];
// The method calls itself recursively until all positions of the key char array have been replaced
if (currentCharPosition < indexOfLastChar)
createNewKey(nextCharPosition, keyChars, keyLength, indexOfLastChar);
// A new key has been created, remove this counter to improve performance
/* The char array will be converted to a string and compared to the password. If the password
* is matched the loop breaks and the password is stored as result. */
if ((new String(keyChars)) == password)
if (!isMatched)
isMatched = true;
result = new String(keyChars);
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