Most Secure Redstone Combo Lock

This is the most secure minecraft combination lock out there.

Includes:

• Mk I Prototype: Smaller, cheaper, more compact, more walking involved.
  
• Mk II Combo Lock: Very Large, more features, easier to understand, compact 10-digit keypad.
  
  

Each lock is capable of virtually infinite combination possibilities.  There are four sequential parts to each combination, with each part consisting of 1-9 digits, in any order.  The system uses a binary decoder to turn a combination of numbers into a single redstone current.  This output goes into an AND gate, and when the "enter" button is pressed, unlocks the next part of the combination.