Sharp Cash Trix

by Dennis Fiery

Editor's Note:  Although readers should always exercise caution in the application of knowledge, the subject matter of this article deserves a special advisory.  Do not attempt to take advantage of this security weakness unless you have the approval of those in charge.  Doing otherwise could risk your future and possibly your life.  Opening a cash register without permission is very different from logging onto a computer without permission, despite what some authorities want us to believe.

There is an interesting security problem with the Sharp ER-3100 cash register.

The Sharp ER-3100 is an inexpensive model that can be fully programmed by the user, but the security problem is about as low-tech as you can get.  I've seen this model being used in bagel stores, pizza places (including the Sbarro chain), libraries, video stores, and elsewhere, so this is a pretty popular choice as far as registers go.  You can recognize the register because it is beige, and it sits on top of a silver-grey cash box.  The register and the box appear to be two separate pieces, but actually they are bolted together as one.  On the back of the register (the side that faces the customer) there is a movable lighted display that shows the cash total in green, and it has the word "Sharp" printed on it in white lettering.

We are all familiar with the great precautions that store-owners take to prevent employee theft.  If you have someone working the register in your store you have to trust them to a certain degree.  But as you know if you've ever had a job behind a counter, the boss usually has a bunch of rules that must be followed so he can keep track of who is using the cash registers and how they are being used.  In some stores, receipts are imprinted with the clerk's name.  In other places a code letter or number is used (the Sharp ER-3100 offers four different letters that can be printed on a receipt: A, B, D, and E).  The store owner can insert a key into the register, turn it, and press a button or series of buttons to print out an activity log, giving a complete breakdown of what money is in the register, what was purchased, and what money was refunded.  Big Brother is definitely smiling about all these precautions bosses take to spy.

All of the above is a good way to keep track of individual transactions, but whenever the cash drawer is open the clerk can swipe out a handful of money.  Cash registers generally have a "No Sale" button on them, which allows the drawer to be opened without a transaction being issued.  "No Sale" is mostly used when someone comes into the store and asks for four quarters for a dollar, or other change.  The "No Sale" button is dangerous because it opens the drawer, and while it's open anything at all could go on, and the boss doesn't have much control over that, except to trust the cashier's honesty.

There are some precautions taken to try to prevent employee theft when a "No Sale" is rung.  First of all, when "No Sale" is pressed, the cash register rings its bell.  If the supervisor or manager is on the other side of the room, they will know that the register is open and the employee will realize that he or she is somewhat under the watchful eyes of their boss.  Also, every time "No Sale" is rung up, that fact is recorded.  Later when the boss prints out an activity log, he or she will see that Cashier B pressed "No Sale" four times that night while Cashier D did not press it at all.  If some money is missing, the four "No Sales" would lead the boss to suspect Cashier B is the culprit.  Many bosses forbid their employees to use the "No Sale" button because they don't want the cash drawer opened unnecessarily for just this reason.

How to Get Around This Security

Now we get to the security laxity in the register.

There is a way to open the Sharp ER-3100 in such a way that the bell does not ring.  Completely silent!  More importantly, by opening the drawer in this way you also bypass the computerized activity log.  The boss will have no records that the register was ever opened.

The cash register rests on four black rubber pads which raise the register off the counter top a little less than half an inch.  This is just enough space to slide one's fingertips underneath the register.  Indeed, this is the method to opening the register.

There is a secret lever under the register.  It's towards the front of the machine on the side facing the customer.  Because it is on the far side away from the cashier, if the cashier wants to access this secret lever, he must lift the register and slide his hand and arm underneath the register to reach the lever on the other side.   hat's where the customer has an advantage - it's actually easier for the customer to open the drawer than the cashier!

The customer has the lever literally inches away from his or her body.  In many pizza parlors and other places that use this register, you can stand by the counter and casually slide your fingers under the register (palm up).  Insert your fingers under the center of the register until you find a rectangular hole in the metal bottom of the register, close to the nearest edge.  Inside this hole you will feel a vertical strip of metal perpendicular to the floor.  Push this metal strip away from you, towards the cashier, and the cash drawer will roll open.

The lever is hard to find at first.  The hole in the bottom of the register is pretty big, and the lever is pretty small.  Also, the lever does not feel like a lever.  It doesn't feel like an "user interface object" that you are supposed to manipulate, and if you were to lift the register and peek underneath you would see that the lever doesn't look like anything special either.

In short, the Sharp people are trying to disguise this lever from casual observation and discovery.  But we know it's there!

Feel around until you find it in the hole, and push on it.  I strongly, strongly advise you to first make sure the store does not have security cameras and no security guards, and preferably that you're good friends with the cashier.  Otherwise you could find yourself in a jail cell where there are no secret levers to get you outta there.  Whenever I see one of these registers in a store or restaurant, I always ask the clerk if they know about the secret way to open the register.  They never do.  I have never met anyone working at a store or restaurant who knew about the hidden lever!  Usually they express disbelief until I demonstrate how easy it is for me to slide my fingers underneath and give the lever a push.

The instruction manual for the register explains the lever as a way to open the cash drawer "when power failure is encountered or the machine becomes out of order."  The brief and grammatically incorrect paragraph describing the lever is pushed all the way to the back of the manual, almost on the last page, and is given under the unassuming title "Opening the Drawer By Hand."

If you ever open one of these registers you can find the instruction manual hidden underneath the till.  After opening the cash drawer, you will see the compartmentalized till which has sections for different money denominations and coins.  Lift out the till slightly to reveal the manual (and possibly other goodies) underneath.

Protecting the Lever

Sometimes a store will install its cash register in such a way that you cannot slide your fingers underneath to access the lever.  For instance, the register may be protected by a raised portion of the counter.

In one library I saw pieces of metal bolted to the counter top as a protective measure against finger-insertions.  There is another way in which the lever can be foiled: if the supervisor locks the cash drawer with the key, then it will not open.  It is rare, however, to find a locked cash drawer, especially during the day when people are coming into the store to buy stuff!  The vast majority of the registers I've seen were freely accessible to anyone who knew about the lever.

Conclusion

One time I was in a music store that used one of these registers, and the cashier was talking to his friend who was leaning against the counter.  The friend happened to bang his elbow on the cash register, and the drawer flung open of its own accord.  The two were surprised (as was I), but I also knew what had happened: the shock of his arm had conducted to the lever, which got rattled back and caused the drawer to fling open.

The Sharp ER-3100 is a good cash register, easy to use, highly programmable, and expandable.  But it does have this one problem.  If you use this model in your store, you should make sure the back is closed off so customers cannot slide fingers underneath.  Either put up a piece of wood or metal in front of the register, or lower the register into a niche or put it up against a wall.  Another alternative is to put a big piece of duct tape over the hole in the bottom of the register.