Put your key in the sandwich bag then wrap that in aluminium foil, carefully sealing three edges. Make sure you can still access the sandwich bag’s opening (the fourth edge that you don’t seal). It’s the same with a fridge. In some cases, the seal on a fridge door will be sufficient to keep the signal from the key in and any external signals out. In other cases, it won’t isolate the key sufficiently to be any use. This Disklabs bag is as well constructed as the larger phone version (left) and has Secured by Design accreditation, too. It also has a handy lip on the flap, so it is easier to pull open. To see how good the item really is, put your mobile phone in it (assuming it fits). Then ring your phone. A fully functioning Faraday bag should prevent the signal getting through to your phone. What makes a good Faraday pouch? At a push we squeezed in a key and a phone, but the Velcro section along the flap wasn’t full width and protection was a bit hit and miss as a result.

Car Key Signal Blocker Pouch with Hook Securing Keyring Car Key Signal Blocker Pouch with Hook Securing Keyring

It makes sense to always use a Faraday bag when the car is on your driveway or in a garage, but also when you’re away from home, because thieves often operate in car parks.

Instructions for use

We like the smart carbon fibre-effect construction and the extra front section, which was useful but wasn’t protected. The bag must be fit for purpose too. Some people might want a Faraday bag that’s portable; some might want one that they can just leave in their house for when they’re at home. The latter might be able to get away with a less robust article. We are also impressed by the two-year replacement guarantee, which shows Halfords’ confidence in the product. We like the bag’s general build and tough feel, and it took either of our phones and a key with a little effort, but it wasn’t elegant. This kind of crime is referred to as ‘keyless theft’ or ‘relay theft’ because of the way the signal is relayed. The whole process can take a team who know what they’re doing less than a minute. How do Faraday pouches work?

Signal Blocking Pouch RFID - Phone Case Signal Defender Signal Blocking Pouch RFID - Phone Case Signal

A poor-quality Faraday bag may stop working because it has failed and can no longer prevent the signal from escaping. Whenever you think your car key might be vulnerable to having its signal grabbed. Ironically, the easiest cars to steal using relay theft are those parked on people’s drives. The thief knows exactly where the keys for that car are: somewhere behind the front door.Bauer Consumer Media Ltd, Company number 01176085; Bauer Radio Limited, Company number: 1394141; Registered office: Media House, Peterborough Business Park, Lynch Wood, Peterborough PE2 6EA and H Bauer Publishing, Company number: LP003328; Registered office: The Lantern, 75 Hampstead Road, London NW1 2PL

Halfords Anti-Theft Car Key Signal Blocker - Black | Halfords UK

We like the second metal-surrounded compartment at the front, which is ideal for credit card protection. It’s this that gives it an edge over similarly priced alternatives.

Features

The Velcro strip extends completely across the bag, which should seal it completely, but although it worked well with the remote key, it failed to prevent both the Bluetooth and WiFi signals getting in, which is a shame.

The best Faraday and RFID key pouches - Car Magazine Products The best Faraday and RFID key pouches - Car Magazine Products

The aim of a Faraday pouch is to contain the signal transmitted from a car’s key. To do this, the bag must be lined with something that doesn’t allow the signal to escape. This is usually metallic and frequently involves a number of layers to ensure the signal is well and truly contained.

Some people might want one to put their mobile phone in; some might want them for their car keys. It’s worth remembering that car keys can differ dramatically in size nowadays too. Do you need a Faraday box for car keys? We like the tough, high- quality feel of the bag’s textured polyester. It’s claimed to suit 99 per cent of key fobs and ours fitted, along with three credit cards that slotted into the protected front section. It took our key and two credit cards, but isn’t particularly big – just a little larger than the Halfords and Olixar. The strong Velcro flap makes it unlikely any stray signals could get in and, in the test, none did. Although manufacturers are taking steps to make keyless-entry vehicles more secure, many models remain vulnerable to technically adept thieves.