Understanding CNC Combination Code Cracking Machines
A CNC combination code cracking machine consists of a stepper motor and a pulse modulation circuit directly connected to the dial of the safe. It is fixed to the safe door using magnets, and the user employs a controller to power the motor and set the cracking mode step by step. The machine needs to set up the starting point, direction of rotation (left/right), position of the dial, etc. When the correct combination is found, the machine automatically stops and displays the code on an LCD, ending the cracking process.
The Mechanics of Combination Locks
Brute Force Attacks on Combination Locks
For a combination lock, the probability of a complete brute-force attack, trying every combination without skipping any, is about 1,000,000 possibilities with a 4-digit code. Manually trying all these combinations as a thief is, of course, nearly impossible. In this case, a CNC code cracking machine is useful. Imagine it takes about 3 hours to try all odd numbers ending in 5, and about 10 hours for all even numbers ending in 2. Eventually, the lock will be opened.
Simulating Human Operations
The machine operates by simulating the human process of opening the safe, starting from a set point and trying all combinations by rotating the dial in increments that match the engraved markings on the code disc. For example, if the code disc is engraved with 100 evenly spaced marks around its circumference, and the cracking machine uses a 200-pulse/rev motor, each step angle is 1.8°. To match the 100-mark step on the dial, the machine sends 2 pulses per step to create a 3.6° step, aligning the motor resolution with the engraved disc resolution.
The Code Cracking Process
From the starting point set by the user, the machine continuously updates the current combination based on the motor’s rotation. Different combinations are tested successively to eliminate incorrect ones. The question is, how does the machine recognize the correct combination and stop the cracking process?
Types of Combination Locks
Blade-Type vs. Gearbox-Type Locks
It is important to note that the cracking machine is placed outside the safe door, completely isolated from the internal gearbox, with no internal sensor to help the machine recognize if the dialed combination is correct or not.
There are two types of combination locks as shown in Figure 1:
Figure 1a and 2a: Blade-Type and Gearbox-Type Combination Locks
Figure 1b and 2b: Operation of Blade-Type and Gearbox-Type Combination Locks
- Blade-Type Lock (Figure 1a and 2a): A blade lock allows or prevents a latch from moving radially when the correct combination is dialed. This latch operates manually, so after the blades are set to the correct positions (correct combination), you must manually push the latch to open the lock.
- Gearbox-Type Lock (Figure 1b and 2b): A gearbox-type lock has a locking lever constantly pressed against the circumference of the disc by a spring. This locking lever automatically falls into a notch on the disc’s circumference when all discs are correctly positioned (correct combination), an automatic process.
Key Differences and Vulnerabilities
Comparing the two types, blade-type locks require fully manual operations even when the combination is correct, whereas gearbox-type locks automatically engage the notch when the combination is correct. This critical difference means only gearbox-type locks can be cracked by a CNC machine.
Countering CNC Combination Code Cracking Machines
The Vulnerability of Gearbox-Type Locks
A CNC code cracking machine only rotates the dial according to various directions with rotation angles matching the resolution of the engraved marks on the dial. Determining when the correct combination is found is a passive behavior of the gearbox, leading to its vulnerability to code cracking. Suppose a CNC machine attempts to crack a blade-type lock. In that case, when the correct combination is dialed, the latch does not automatically engage, causing the machine to quickly skip it and move to the next combination. No sensor detects the correct or incorrect combination state when the machine is only placed outside the safe door.
Disabling the CNC Cracking Machine
To crack a blade-type lock, the only way is to create a load that forces the latch to always be pushed radially so that it moves radially relative to the code disc as soon as the correct combination is found. From this observation, it is possible to completely disable the CNC cracking machine by cutting the mechanical link between the horizontal bar and its external drive dial using a lock shield disc. Only safes designed by RDIP are capable of doing this. Ultimately, the CNC combination code cracking machine is not an invincible monster. The self-engaging feature of the locking lever in gearbox-type locks turns against it when facing a cracking machine. All factors have two sides, as the gearbox prevents it from being observed by an endoscope, a capability blade-type locks do not possess.
Gearbox with a Cover but Without an Automatic Latch
Figure 3: Gearbox with a Cover but Without an Automatic Latch to Prevent CNC Code Cracking
Conclusion
The Importance of Understanding Lock Types
Understanding the types of locks and their vulnerabilities is crucial in developing strategies to counter CNC combination code cracking machines. By focusing on the inherent strengths and weaknesses of each lock type, security professionals can better protect against unauthorized access.
Recommendations for Enhanced Security
For enhanced security, consider using blade-type locks with additional mechanical barriers or shield discs to prevent CNC cracking machines from easily determining the correct combination. Continuously innovate and test new methods to stay ahead of potential threats.
By leveraging knowledge of both mechanical and electronic systems, security engineers can create robust solutions that protect against even the most sophisticated code-cracking machines.
