Faraday Bag

A Faraday bag is a portable enclosure lined with conductive material that blocks electromagnetic signals, isolating whatever is inside from Wi-Fi, Bluetooth, cellular, GPS, and RFID communication. Quality bags attenuate signals by roughly 60 to 100 decibels, enough to silence a phone or hardware wallet completely.

Why it matters

Bitcoin security is ultimately the security of key material and the devices that touch it. Faraday bags are used to transport and store hardware wallets and signing devices so they cannot be reached by wireless attacks, to quarantine phones during sensitive operations, and to protect backup electronics against electromagnetic pulses and solar-storm scenarios that some holders include in their threat models.

The bags are standard equipment in digital forensics, where police use them to stop seized phones from being wiped remotely, a useful sign that the shielding is taken seriously by professionals. For most holders they are a low-cost layer in a defense-in-depth setup rather than a necessity, since a hardware wallet with no radios has little to shield.

In the gold vs bitcoin debate

The Faraday bag illustrates how bitcoin translates physical security into informational security. Gold owners buy safes and vault space against theft of mass; bitcoin owners buy shielding, steel seed plates, and geographic key separation against theft of information. The budgets are smaller, but the discipline required is arguably greater.