GB2536728A

GB2536728A - Improvements in combination lock tumbler defence mechanisms

Info

Publication number: GB2536728A
Application number: GB1505362.2A
Authority: GB
Inventors: Dewi Robin Littler Mike
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-03-27
Filing date: 2015-03-27
Publication date: 2016-09-28
Also published as: GB201505362D0

Abstract

A combination or permutation lock tumbler defense mechanism with having rotating numerically selective tumblers 2 each with a true gate opening 4 and a plurality of partial or false gate openings, notches or slots 5-14 located on the inner service 3 of the tumbles. A number of tumblers may be mounted on a fence (16, Fig. 2) having a corresponding number of posts (18, Fig 2) via the holes 15. Each post may project from the fence into recess 23 of each tumblers when in the locked condition. Rotation of the tumblers aligns each post with a gate opening 4-14. The partial false notches act to fool a potential thief attempting to feel the interaction of a post with a gate opening, preventing unauthorized opening. The fence may have female and male sections (21, 17 respectively Fig 2), the female section having a slot for the fence posts, which may be retained against the tumblers by a spring clip 19.

Description

I

PATENT APPLICATION OF

MIKE DEM ROBIN LITTLER

FOR

IMPROVEMENTS IN COMBINATION LOCK TUMBLER DEFENCE MECHANISMS

Field of the Invention

The present invention relates to the use of combination locks in various forms and their ability to delay or withstand unwarranted interference or attempts to unlock their mechanism.

Background

The use of combination locks is widely known and they are applied to various situations where items or buildings require protection through locking devices. A combination lock is a type of lock in which a sequence of numbers or symbols is used to open the lock instead of a physical key.

In different varieties of lock, the sequence may be entered using a single rotating dial which interacts with several discs or cams, by using a set of several rotating discs with inscribed numerals which directly interact with the locking mechanism, or through an electronic or mechanical keypad. Types range from inexpensive three-digit luggage locks to high-security safes. Unlike a regular padlock, combination locks do not use keys.

One of the simplest types of combination lock, often seen in low-security bicycle locks and in briefcases, uses several rotating discs with notches cut into them. The lock is secured by a pin with several teeth on it which hook into the rotating discs. Only when the notches in the discs align with the teeth on the pin, can the lock can be opened.

There are two standard attacks on this type of combination lock -the brute force, or sequential attack and a gate sensing attack.

The brute force or sequential attack involves trying every combination until the correct one is found. This attack method defines the baseline security for the lock, and is determined by the number of tumblers used and the number of positions per tumbler. Hence if only three tumblers are used with six positions each, there will be 6x6x6 or 216 possible combinations. If a brute force attack is made on this, and the attacker can try four combinations a second, then the delay caused by the lock will be a maximum of 216/4 or 54 seconds. However, when the lock is made with ten positions per tumbler and four tumblers, there are now 10,000 possible combinations and the maximum delay is now 10,000/4 or 40 minutes. This is quite adequate as a security device (but may be extended by adding further tumblers as required) The gate detection method is far more effective as an attack. This is based on the ability of the attacker to detect the open position of a single tumbler (independently of the position of any of the other tumblers). The first requirement of this method is that the lock be placed under tension as would be required to open it with the correct combination. In this state, one of the tumblers will be stiff to turn, as it is in contact with one of the posts that prevent the lock from opening. This tumbler is turned by the attacker, and as the post aligns with the open gate in the tumbler, there is movement of the post into the gate, and the tumbler is reluctant to turn any further. The tension is transferred to a different post acting on one of the other tumblers, and that tumbler becomes stiff to turn, and the process is repeated. In this attack with a four tumbler design having ten positions per tumbler, the attacker needs to try a maximum of ten numbers per tumbler, 40 numbers in all, at 4 per second, and the lock may be opened in as little as ten seconds, which is very little different to having the correct combination.

Although manufacturing differences between locks may make this process more or less difficult, it remains an effective attack method on most of these simple combination locks.

The present invention aims to make additional design improvements to the tumbler to help delay or prevent this method of unwarranted opening of a combination lock.

Summary of the invention

The current invention adds false gates to all positions of all the tumblers of a combination lock, such that the gate detection attack is rendered ineffective (or very much more difficult and time consuming) thereby improving the security of the lock to nearer its theoretical maximum based on the brute force or sequential attack.

According to the present invention there is provided a combination lock with an arbitrary number of rotating tumblers set into the main lock body, these have numbers to their perimeter in the familiar way; listing usually from number 1 (one) upwards.

These tumblers are aligned side by side and they are typically retained upon and rotate around a tubular central member.

The central tube on which the discs rotate is both hollow and slotted to permit the insertion and removal of the other lock member, the fence. The fence is a member that fits inside the hollow spindle that retains the discs. The fence has posts protruding from its side, through the slot in the tube, and into the space occupied by the tumblers. There is one post per tumbler on the fence. With the tumblers set to the open position, all of their gates align with the slot, and the fence may be passed through them. Rotating the tumblers with the lock closed moves the gates out of alignment and the fence cannot be moved, as the tumblers now block movement of the fence's posts.

This standard form of combination lock is vulnerable to an attack, where the lock is put under tension. In this state one of the tumblers will be obstructing the movement of the fence (other half of the lock when using a chain version).

By rotating this tumbler a position at a time it is possible to feel when the fence falls into the gate on the tumbler. This is repeated for each of the tumblers and the lock is opened. Instead of causing hours of delay, the lock has only managed a few minutes of delay, and is ineffective.

The solution is to provide a masking or illusion as to the true position of the gate in combination with the fence or pin.

By adding a partial (false) gate in every position of the tumbler, it becomes almost impossible to detect when the tumbler is in the open position, because the fence now moves into an open gate in every position. Previously it only moved in one position, which would have provided the attacker with a clear indicator of the gate open position. This renders the standard (gate detection) method of attacking the lock ineffective or at least many times more difficult to administer.

This will apply to all combination locks that use the alignment of multiple gates to control the movement of the locking member.

Thus; A smooth surface single gate tumbler will locate or 'snag' only with the tumbler in the open position (while under tension). This gives away the tumbler open position with just one full rotation of the tumbler. The time to open the lock is then only the time to rotate each tumbler in turn to its open locating or "snagging" position, often a matter of seconds in practice.

However, with a partial gate in every position, every tumbler will locate or 'snag' in every single position, whether correct or incorrect alike. This makes it very much more difficult to identify any tumblers open position.

Brief description of figures

Figures 1 shows the tumbler, with its added false gates, in dimensional views.

Figures 2 show the tumblers with false gates and lock elements as an exploded view Figures 3 show a close view of the fence section and a single tumbler rotating over it.

Figures 4 show a full dimension of the tumbler and its partial gates and full gate, with the fence recess removed for viewing purposes.

Figures 5 show a sectional example of the way in which the partial gates cause the same sensation of a gate in every tumbler position, and thereby defeat the gate detection attack.

Detailed description of figures

A typical embodiment of the invention is illustrated in Figure 1. The partially gated tumbler 1 is of a round form having a vertical walled depth of a tumbler body 2 in known composition and comparable to other lock tumblers.

To the receiving area of the tumbler body 2 is a circular inner surface 3 which is an inclusive plane that is divided partially by centrally located sectionals. These sectionals form a circular group of cut away gates which contact with an inserted fence post. The cut away areas are of an elongated square cleft and comprise of correct gate opening 4, partial gate opening 5 partial gate opening 6, partial gate opening 8, partial gate opening 9, partial gate opening 10, partial gate opening, 11, partial gate opening 12, partial gate opening 13 and partial gate opening 14, as shown in Figure 1.

Each of the number gate opening are partial in size and depth in comparison with the full or correct gate opening 4, as shown. Between each squared cleft of the partial opening are shoulders 7, which form part of the remaining shaped body 2 and thus the tumbler circular inner surface 3. These combined shoulders and partial gate openings are in a round and central to this collaboration is a single hole opening 15, as shown in Figure 1 which receives the inserted fence, not shown in this figure but shown in figure 2.

The partially gated tumbler 1, is round and provides a recessed collar like area to its very leading edge, this recess for the fence 23 allows the tumbler to be rotated while the fence post is present.

In figure 2, the fence 16, as shown is presented in known forms and is a solid cylindric metal variant which provides several teeth or post members 18, aligned and equally spaced to its surface. These post members 18 pass through the true gate 4, while the core of the fence 17 passes through the centrally located single hole opening 15A which is a though opening to the tumblers 1A, which in turn forms the cut away clefts of the full gate 4 and partial gate openings 5, 6, 8, 9, 10, 11, 12, 13 and 14 to its circular edge. This is possible as in the known way the tumblers are aligned to allow passage of the pin members 18 on initial use of the lock. To the exterior of the tumblers 1 and 1A are numeral livery ranging from 1 upwards, commonly 1-10.

The fence insertion section 17, which is a male fitting, engages with the female receiving area 21, which is located to the opposing end of the lock mechanism forming part of the connecting female lock section 20.

Once the male 17 and female 21 sections are engaged, with the male post members 18 passing between the tumblers 1A, they are assisted by a variable spring clip 19 which ads retention against the tumblers 1A, once all sections are aligned and engaged the lock is closed.

At this point the fence 16 is able to pass through the single centre hole 15A, as shown in Figure 2. This being due; in the known way; to the pin members 18 being able to pass through the gate 4 due to correct alignment.

Once the combination has been 'scrambled' wherein the numerals have been purposely moved into different positions by the user to guise the code, the fence pin members 18 inside the tumblers 1A are unable to be extracted as they are held due to the gate openings 4 that correspond between each tumbler interior and the pin members 18 not being aligned.

The tumblers 1A, as shown in Figure 2, will still rotate around the fence 16. The attacker may attempt to rotate a tumbler 1A and see if they are able to 'feel' or 'hear when the pin member 18 relating to each tumbler 1A is in the correct alignment inside with the true gate 4.

As they rotate the tumbler 1A the pin member will contact or 'snag' with the partial gate openings 5, 6, 8, 9, 10, 11, 12, 13 and 14 in turn.

Thus the ability to feel or listen for a single engagement of the fence posts 18 and the true gate 4, as is known, is eliminated and confused by adding many partial openings that appear to be the correct gate and do so on each turn of the rotating tumblers.

Figure 3 demonstrates how the fence 168 provides the extended member of the fence insert section 17B and male pin area 22B as a male fitting; passing through the tumbler 18 centrally, accommodated by the recess for the fence 23B. The member of the fence insert section 178 is derived as a solid structure of steel moreover and has posts 188 aligned and equally spaced to its surface as shown.

On rotation of the tumbler 1B, the fence posts18B will locate or 'snag' on the many partial gate openings, 58 and 12B of this number shown here; with each turn gradient, these gradients being of equal distance apart from each other as is governed by the precise distance between each gate opening to include the correct gate as provided within the circle. Thus, upon rotation the attacker feels many openings which creates a confusion as to which is the true gate to engage the locks opening.

This is demonstrated in Figure 5 which shows the tumblers 1D, with the fence insert section 170 having its pins 180 held in a partial gate 9D, the fence insert section 170 cannot be removed and thus the lock cannot be opened, even though the remaining two tumblers have the pins 18D in the correct gate.

In order to rotate a tumbler further, the tension on the fence must be reversed, to remove the pin 180 from the false gate 9D. Even if the attacker is able to sense the difference between the false gate and the true gate, the time to test the gate has been increased significantly when compared with a plain smooth tumbler with a single gate. With the plain smooth tumbler, tension may be applied constantly as the tumbler is rotated and it will snag in only one position. With false gates, tension has to be applied to test the gate, then removed to permit rotation to the next gate. Even if gate detection is still possible the time to test a gate has been increased by about 4-5 times, and consequently the lock effectiveness is increased by the same factor.

Claims

Claims 1. A combination lock tumbler defence mechanism has rotating numerically selective tumblers with additional internal gate openings that are partial only.
2. A combination lock tumbler defence mechanism as claimed in claim 1 wherein it has internal gate openings one of which is the correct gate and multiple others that are partial false gates.
3. A combination lock tumbler defence mechanism as claimed in claim 2 wherein, the correct gate allows passage of the lock fence and the partial gates do not.
4. A combination lock tumbler defence mechanism wherein, the extending post members of an inserted lock fence; contact with each of the multiple partial gate openings as the tumbler is rotated, due to the partial gate openings being positioned suitably to allow the extending pin members to do so.
5. A combination lock tumbler defence mechanism as claimed in claim 4 wherein; extending pin members which are part of a lock fence exterior and are presented as an equally spaced alignment, locate partially with rotating partial gate openings; as a repeated action; as long as the tumbler is rotated.
6. A combination lock tumbler defence mechanism wherein; a perpetrator who is attempting to judge or feel when the pin members of a lock gate are seated in the correct gate opening of a rotating tumbler; has to decipher from the collective number of full and partial gates now presented inside the tumbler; which one of these is the point at which to stop the tumbler rotation.
7. A combination lock tumbler defence mechanism as claimed in claim 6 wherein; a perpetrator has to decipher from the collective number of full and partial gates now presented inside the tumbler; which one of these is the point at which to stop the tumbler rotation and thus must repeat this decision for each of the tumblers in turn.
8. A combination lock tumbler defence mechanism wherein; a lock fence pin member may appear to be correctly locating or seating with a lock tumbler gate but may actually be 'snagging' or contacting with a false partial gate therein.
9. A combination lock tumbler defence mechanism as claimed in claim 8 wherein; because the partial gate and their openings provide a false feel to an attacker of whether or not a lock fence has connected correctly with a lock gate, the attacker has to decide from a multiple of options instead of one option, when picking or trying to attack a combination lock.
10. A combination lock tumbler defence mechanism wherein, the partial gates are of exacting form to the full or correct gate but are partial in depth or length to the full or correct gate.
11.A combination lock tumbler defence mechanism as claimed in all previous claims is an application to add additional partial lock gates to the interior of a combination lock tumbler; to mask the real tumbler gate from perpetrators who rotate combination lock tumbiers to feel or judge when the fence and gate are aligned internally on each tumbler; to enable them to unlock the lock without the numeric security code, thus confusing this normally basic decision by cloaking the real gate opening with a collection of false ones creating a long delay or even preventing the lock from being entered by the gate sensing method.