Albert Einstein kept a portrait of the 19th-century scientist Michael Faraday on his wall, alongside a picture of Isaac Newton. Genius recognizes genius: Faraday’s many discoveries led to electric motors, to electricity being put to practical use in technology, and to the concept of electromagnetic fields in physics. Faraday also figured out that an enclosure made of a mesh of conductive metal can absorb and redistribute electromagnetic interference. It is this work that’s honored every time someone slips a cell phone into a pouch coated with metal, made for the specific purpose of preventing signals from getting in or out. The low-tech hack shields phones from digital buttinskies by blocking cellular signals, Wi-Fi, GPS, NFC, RFID, and Bluetooth. Privacy-craving citizens can put their phone into a Faraday pouch like this one from Silent Pocket ($60 and up), where a metal lining renders the device inside invisible to snoops. “The biggest threat is a law enforcement agency using the signals on your phone to prove you were at a protest or demonstration that they decide later is illegal, and using that information to arrest you,” says Cooper Quintin, a security researcher with the Electronic Frontier Foundation, a nonprofit digital rights group. He doesn’t believe a Faraday cage would protect a phone any better than turning it off or putting it into airplane mode, but says the cage’s advantage is that it’s harder to forget or screw up. If you know you’re the forgetful type, though, or just don’t trust airplane mode on your phone, a Faraday cage means your vanishing act is in the bag.
→ Three layers of nickel- and copper-coated fabric—the Faraday cage—mean stronger protection than just one layer
→ Wear and tear on the metal fabric would impede its signal-squelching abilities; a soft liner protects it from abrasion.
→ A layer of thin cotton padding helps the leather on or nylon outer shell protect the phone against bumps and drops.
→ Silent Pocket also sells its Faraday fabric separately ($26 per square meter), so you can fashion your own DIY pouch. If you’d rather just get a pre-made pouch, they are available from Amazon or directly from Silent Pocket.
Updated September 22 to clarify Cooper Quintin’s position on the usefulness of using a Faraday cage for personal security.
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