Really slow brute forcer for encrypted wallet. If you forget it and know the beginning of the password you may be able to get it. However this can only try 10 passwords a second :( Adapted from a script posted on bitcointalk.

brute.rb

#!/usr/bin/ruby -w

=begin
How to use, windows:

go to C:/Program Files (x86)/Bitcoin/daemon/
and execute ".\bitcoin -help"

You will need to create bitcoin.conf file @:
C:\Users\usr\AppData\Roaming\Bitcoin

Paste in the password that help tells you do use.

Now start bitcoind in daemon mode:
".\bitcoin -daemon"

Go to the command line and tst this:

"C:/Program Files (x86)/Bitcoin/daemon/bitcoind.exe" walletpassphrase correctapass 5
--> this should have no result if correct

"C:/Program Files (x86)/Bitcoin/daemon/bitcoind.exe" walletpassphrase wrongpass 5
--> should return: error: {"code":-14,"message":"Error: The wallet passphrase entered was incorrect."}

Make sure you put quotes around the path.

Run the sscript:

C:\Program Files (x86)\Bitcoin\daemon> ruby "C:\pathtoscript\brute_forcer.rb"

=end

class Cracker
  def initialize(coindloc, basepass, char_array, password_range)
    @coindlocation = coindloc
    @basepassword = basepass
    @char_array = char_array
    @password_range = password_range
    @prng = Random.new
  end

  ## This will print the results and actually run the command.
  def password_correct?(phrase)
    
    puts "#{@coindlocation} walletpassphrase #{@basepassword}#{phrase} 5"
    system("#{@coindlocation} walletpassphrase #{@basepassword}#{phrase} 5")
    if $?.exitstatus == 0
      puts "Found it: #{@basepassword}#{phrase}\n" * 10
      exit 0
    elsif $?.exitstatus == 14
      puts "failed on: #{@basepassword}#{phrase}\n"
    else
      puts "unknown error occured. check path"
    end
    return false
  end

  # this builds the password guess
  def generate_password( perm_number, password_length )
    password=""
    (1..password_length).each do |char_number| # loop through characters
      char_reference = (perm_number / @char_array.length**(char_number-1)).floor % @char_array.length
      character = @char_array[char_reference]
      password << character
    end
    password
  end

  
  def do_combination( num_combinations, password_length )
    (0..num_combinations-1).each do |perm_number| # loop through combinations for a given length
      password = generate_password( perm_number, password_length )
      return password, perm_number if password_correct?(password)
    end
  end

  def crack()
    (@password_range).each do |password_length|  # loop to gradually increase password length
      num_combinations=@char_array.length**password_length
      password, perm_number = do_combination(num_combinations, password_length)
      if password
        puts "#{password} | Access Granted | #{perm_number} / #{num_combinations}\n"
      end
    end
  end
end

# I removed characters I was sure I didn't use
#characters = "*abcdefghijklmnopqrstuvwyz".split(//) # for if you have no idea
characters = "ghjxcviopbnmrtywe".split(//) #e.g. for typos
basepass = "somebasepass"
coindloc = '"C:\Program Files (x86)\Bitcoin\daemon\bitcoind.exe"'


cracker = Cracker.new( coindloc, basepass, characters, [2,3,4] )
password = cracker.crack()

puts "No luck."
exit 1