Introduction to Changing Combination Lock Codes
This article clarifies for MimirVault readers, security enthusiasts, and general safe users how combination lock codes can be changed. Understanding the principle behind combination lock codes and how they can be altered is essential for enhancing security and ensuring the proper use of safes.
The Basic Principle of Combination Locks
Structure of Combination Locks
The basic principle of a combination lock consists of a series of slotted discs with notches on the face, all arranged on the same rotating shaft. Only one of these discs receives torque from the dial, referred to as the active disc. All other discs rotate freely on the dial shaft and receive torque transmitted through the notches on the face of the adjacent disc without receiving direct torque from the dial shaft.
Figure 1: Combination Lock with Face Notch Drive Discs
Functioning of the Active and Passive Discs
The absolute angular position of this active disc’s notch compared to the zero mark on the engraved dial is completely determined (for instance, they are aligned with each other). The passive discs all have notches on the face; the middle discs have notches on both faces to receive torque from the preceding disc and transmit torque to the following disc, while the outermost disc has notches on one face as it only receives torque and does not transmit it further.
Changing the Combination Code
Adjusting the Angular Position
To change the combination code, it is necessary to change the absolute angular position between the active disc and the dial shaft to a new position for the active disc and change the notch position relative to the face notch position on the passive discs. With the structure in Figure 1, each disc consists of two parts linked by an internal gear ring. Sliding along the shaft can separate these parts and rotate them by an angle to switch to a new code, then reassemble them at the new angular position, resulting in a new combination code. However, this structure is inconvenient because the entire lock must be disassembled each time the code is changed due to the need to slide along the shaft to disassemble the internal-external gear ring.
Figure 2: Structure of Discs Allowing Code Change without Disassembling the Lock
Figure 3: Enlarged View of the Internal-External Gear Ring
Simplifying the Code Change Process
To avoid disassembling the lock each time the code is changed, the code disc is slightly modified as shown in Figure 2. If the cam drive is rotated by 90° using the square hole in Figure 2, the C-shaped external gear ring, instead of being closed in an O-shape, will expand in diameter and separate from the internal gear ring. At this point, the internal gear ring can be freely rotated to change the absolute angular position between the face notch and the notch on the disc’s circumference. Clearly, this structure is more convenient for changing the code than the method shown in Figure 1. However, this disc structure is quite complex and therefore expensive.
Cost-Effective Alternatives
Blade-Type Combination Lock Disc
To reduce costs, a cheaper type of blade combination lock disc as shown in Figure 4 has been used.
Figure 4: Blade-Type Combination Lock
In Figure 4a (left), the active disc is fixed to the dial shaft with a split pin. To change the lock code, the screw serving as the torque notch between the seven available holes on the active disc must be moved. This lock does not allow for preset codes like the previous methods; instead, the code is formed randomly, and whatever code is generated must be used. Even cheaper, the method in Figure 4b (right) has only two screw positions that can be swapped.
Countering Code Cracking Methods
Sound-Based Code Cracking
Although it may seem unrelated to the topic of this article, with smooth discs around the entire circumference having only one notch as shown in Figures 1 and 2, if the discs’ concentricity is low and the roundness tolerance of the outer ring is large, a thief can crack the code by listening to the disc’s movements. Each time the notch reaches the correct position, the locking lever will slightly move toward the disc’s center, suggesting the correct combination to the code cracker.
Camouflaging Against Sound-Based Attacks
To counter this sound-based cracking method, Figure 4 shows the manufacture of multiple notches around the disc’s circumference, but only one notch is deep enough to unlock, while all notches create noise when reaching the correct position. This camouflage is very effective against sound-based lock pickers. Due to the manufacturing tolerances in mechanical production, this camouflage method has never become obsolete.
Conclusion
Enhancing Security with Proper Code Changing Techniques
Understanding the principle of changing combination lock codes and implementing the correct techniques is crucial for maintaining high security standards. Whether using the more advanced internal-external gear ring mechanism or the cost-effective blade-type discs, the ability to change lock codes efficiently and securely enhances the overall security of the safe.
Recommendations for Safe Users
Safe users should familiarize themselves with the specific lock mechanisms of their safes and follow the recommended procedures for changing codes. This knowledge not only improves security but also ensures the safe’s longevity and reliability. For those interested in advanced security techniques, exploring more complex locking mechanisms and staying informed about the latest developments in security technology is advisable.
