Can I Unlock Other People's Cars With My Remote?

iStock/dobok
iStock/dobok

Jason English, our esteemed editor, wonders, "How many other Camrys would my remote unlock? Is it really 1:1, or is there a chance my fob would open a Camry in Phoenix or Toronto?"

When you push a button on your car remote or garage door opener, a radio transmitter inside sends a signal containing a numeric code to a receiver in the car (or in the garage). When it gets the signal, the receiver tells the car (or the garage door controls) to lock or unlock (or open or close)—or whatever it's supposed to do given the button you pushed.

When remote garage door openers first came out in the 1950s, the transmitters in the remotes sent out a single signal. This was all well and good as long as you were the only person on your block with a garage door opener. But as they became more common, you could open any garage you wanted, because all remotes worked on the same signal. A security breakthrough came 20 years later when DIP switches—sets of eight manual electric switches packaged in a group and attached to a printed circuit board—were added. By setting the eight switches to a certain arrangement inside both the transmitter and the receiver, you had some control over the 8-bit code that they shared. The DIP switches could provide 256 possible codes. So while some security was provided, areas with lots of garage door remotes were still prone to code doubling and people opening up their neighbors' doors.

Early remote entry systems for cars were slightly more advanced. The system for each car had a unique code set by the manufacturer and used by that car's transmitter-receiver pair alone. The ratio really was 1:1. Just as my car lock or yours wouldn't open for Jason's key, our receivers wouldn't have responded to his transmitter's signal. These systems had their own problem: while the codes were unique to their cars, the same code was transmitted every time you used the remote. A radio transceiver called a "code grabber" could be used to intercept, store and retransmit the code later on. It was like having your key stolen and copied, without you knowing, while you were putting it in the keyhole and opening the door.

To combat the problem, manufacturers began using rolling codes (or hopping codes) in the mid-1990s. Instead of using a single fixed code, these newer systems use a set of rolling codes that change every time the remote is used. Now when you use the remote, the transmitter sends the current code to the receiver (most systems use 40-bit codes or longer, allowing for more than 1 trillion different combinations). If the receiver gets the current code, it responds; if not, it does nothing. The transmitter and receiver then "roll" the code using the same pseudorandom number generator (PRNG). When the transmitter sends the current code, it uses the PRNG to create a new code and remembers it. After receiving the current code, the receiver uses the same PRNG with the same original seed (the number that initiates the PRNG) to generate a new code. Using this method, the transmitter and the receiver generate matching sequences of codes and are synchronized (and, of course, all the information that's transmitted is encrypted).

What if you press a button on the remote while you're away from the car, generating a new code on the transmitter and desynchronizing the system? The receiver forgives your human error and accepts any of the next X valid codes in the code sequence (the number of "look-ahead" codes the receiver accepts varies among manufacturers). Push the button one too many times, though, and the receiver will ignore the remote and you'll have to resync the system.

Modern remote keyless entry systems are pretty secure, but there is a slight chance Jason could open another Camry if he wants to walk up to one and press the unlock button on his remote (assuming it uses a 40-bit code) one trillion, ninety-nine billion, five hundred eleven million, six hundred twenty-seven thousand, seven hundred and seventy-six times, running through all the possible codes his remote could transmit until one works (assuming he can hit the button once every second without taking any breaks, he'll need just shy of 34,842 years to do so). He'll also have to hope that the Camry he's trying to open has a receiver that uses a 40-bit like his remote, and isn't a newer model that might use a 66-bit code with 7.3 x 1019 possible codes.

Amazon's Under-the-Radar Coupon Page Features Deals on Home Goods, Electronics, and Groceries

Stock Catalog, Flickr // CC BY 2.0
Stock Catalog, Flickr // CC BY 2.0

This article contains affiliate links to products selected by our editors. Mental Floss may receive a commission for purchases made through these links.

Now that Prime Day is over, and with Black Friday and Cyber Monday still a few weeks away, online deals may seem harder to come by. And while it can be a hassle to scour the internet for promo codes, buy-one-get-one deals, and flash sales, Amazon actually has an extensive coupon page you might not know about that features deals to look through every day.

As pointed out by People, the coupon page breaks deals down by categories, like electronics, home & kitchen, and groceries (the coupons even work with SNAP benefits). Since most of the deals revolve around the essentials, it's easy to stock up on items like Cottonelle toilet paper, Tide Pods, Cascade dishwasher detergent, and a 50 pack of surgical masks whenever you're running low.

But the low prices don't just stop at necessities. If you’re looking for the best deal on headphones, all you have to do is go to the electronics coupon page and it will bring up a deal on these COWIN E7 PRO noise-canceling headphones, which are now $80, thanks to a $10 coupon you could have missed.

Alternatively, if you are looking for deals on specific brands, you can search for their coupons from the page. So if you've had your eye on the Homall S-Racer gaming chair, you’ll find there's currently a coupon that saves you 5 percent, thanks to a simple search.

To discover all the deals you have been missing out on, head over to the Amazon Coupons page.

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Why Do We Have Daylight Saving Time?

Patrick Daxenbichler/iStock via Getty Images
Patrick Daxenbichler/iStock via Getty Images

As you drag your time-confused body out of bed at what seems like a shockingly late hour next week, you might find yourself wondering why on Earth we even have Daylight Saving Time.

Though Benjamin Franklin was mostly joking when he suggested it as a money-saving tactic in a satirical essay from 1784, others who later proposed the idea were totally serious. In 1895, entomologist George Vernon Hudson pitched it to the Royal Society in New Zealand as a way to prolong daylight for bug-hunting purposes, and William Willett spent the early 1900s lobbying British Parliament to adopt an 80-minute time jump in April; neither man was successful.

During World War I, however, the need to conserve energy—which, at the time, chiefly came from coal—increased, and Germany was the first to give Daylight Saving Time the green light in 1916. Britain and other European countries quickly followed suit, and the U.S. entered the game in 1918. The practice was dropped almost everywhere after the war, but it was widely resurrected just a few decades later during World War II.

After that war ended, the U.S. abandoned DST yet again—sort of. Without any official legislation, the country devolved into a jumble of conflicting practices. According to History.com, Iowa had 23 different pairs of start and end dates for DST in 1965, while other areas of the country didn’t observe DST at all.

In 1966, Congress put an end to the chaos by passing the Uniform Time Act, which specified that DST would begin at 2:00 a.m. on the last Sunday in April, and end at the same time on the last Sunday in October. (The Energy Policy Act of 2005 extended DST by shifting these dates to the second Sunday in March and the first Sunday in November.) It didn’t require that all states and territories actually observe DST, and some of them didn’t—Arizona and Hawaii still don’t.

Throughout its long, lurching history, the supposed merits of Daylight Saving Time have always been about cutting down on electricity usage and conserving energy in general. But, as Live Science reports, experts disagree on whether this actually works. Some studies suggest that while the extra daylight hour might decrease lighting-related electricity use, it also means people could be keeping their air conditioners running for long enough that it increases the overall usage of electricity.

If your extended night’s sleep seems to have left you with a little extra time on your hands, see how DST affects your part of the country here.

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