Casa Blog - Bitcoin Security Made Easy

When your wealth is on the line, you want the best protection money can buy. At Casa, we are always exploring the most extreme ways to protect our clients and their data. And our Casa Faraday Bags are just one of many ways you can harden the protection for your bitcoin and other assets.

What’s a Faraday bag?

A Faraday bag is an enclosure for electronic devices designed to block electromagnetic signals from entering or leaving the bag. Today, they are popular with intelligence and military officers out in the field as well as cybersecurity professionals. There are Faraday bags built to contain phones, laptops, and hard drives.

The Casa Faraday Bag is a physical shield designed specifically for your hardware wallets that is not only dust and water resistant, but also blocks electromagnetic radiation – cellular, GPS, Bluetooth, WiFi, RFID, NFC radio waves and more.

The bags are available for Casa Premium members and Private Clients, for whom we work to deploy every failsafe in our arsenal.

The problem of protecting your hardware wallet

Being self-sovereign over your data and wealth has many benefits, but it also introduces new problems and responsibilities with managing keys. Hardware wallets like those from Trezor and Ledger are a great way to ease the burden, but we’ve noticed people can be careless with physical protection of their devices. We’ve seen hardware wallets linked to millions of dollars sitting out unprotected on a desk, or even worse — being casually carried around in someone’s pocket.

Hardware wallets are sensitive electronic devices subject to the same risks as other electronics, such as water and dust damage, accidental force damage, bit rot (the deterioration in performance and integrity of electronic components) and more.

Hardware wallets, like most electronics, can also be damaged by electromagnetic radiation. Fortunately, a protection against this threat was found by Michael Faraday many years ago.


Faraday cages are named after Michael Faraday, the English scientist who invented them back in 1836. He built the first Faraday cage by building a room coated in metal foil. Despite high-voltage discharges from generators onto the exterior of the room, he showed that there was no charge found inside the walls of the room.

This same concept works with Faraday bags, which work by redistributing electric charges around the bag's exterior, canceling the electric field's effect on the interior of the bag. Preventing gaps in your exterior with a foldover or roll closure on your Faraday bag is important for that reason. Faraday bags can protect devices that can be affected by radio: mobile phones, laptops, passports (all U.S. passports issued after 2007 have an RFID chip embedded) — you name it.

If you put a device into a Faraday bag, the device might still listen for incoming radio emissions, but none will reach it. Your device may also try to transmit and communicate externally, but its waves won't exit the bag.

Most hardware wallets only power on when connected to a computer. Most do not emit radio waves. So why go to the extreme of using a full Faraday bag? Because hardware wallets are already becoming the most important and sensitive electronics that we use on a regular basis.The real-world effects of exposure to various types of electromagnetic radiation on sensitive electronics are hard to predict. Blanket protection with a Faraday bag is an easy first step, but there’s still a lot of research to do.

Electromagnetism is all around us but imperceptible to humans. This makes it prudent to protect devices containing private keys from electromagnetic pulses.

Why you should protect devices from electromagnetic pulses (EMP)

The extreme risk case for hardware wallet electronics is protection against an electromagnetic pulse (EMP), a strong wave of electromagnetic energy. EMPs are most commonly linked with nuclear weapons blasts or solar weather events like a coronal mass ejection, and our understanding of them is evolving. Nations are increasingly monitoring the emerging threats of EMP weapons that target satellites and other communications infrastructure.

What many don’t know is that smaller EMPs can be triggered by lightning strikes or even power line surges. During our research, we also heard from friends in the defense industry that EMP guns now exist — with claims that a focused blast can disable any unshielded electronics in the vicinity.

Using a Casa Faraday Bag will NOT fully protect your devices from an EMP blast, but we do believe it will increase your device's odds of survival over leaving it totally unshielded.

This is an ongoing area of research. It will take years of study and experiments to arrive at the best possible protection for your hardware wallets and other signing devices. We will update our product recommendations to clients as we learn more.

Get your own Faraday bags with a secure 5-key vault

Ready to block those pesky transmissions? You can use Faraday bags to fortify your cold storage with a Casa Premium membership.  

Premium members receive a welcome package delivered to their door, complete with three new hardware wallets and Casa Faraday bags to go with them. That way, whenever you’re not actively signing transactions, you can keep your devices in cold storage from the internet and the elements.

Once you have your package, Casa advisors guide you through step by step how to set up and use each device so you never have to go it alone with your self-custody. It feels good knowing that help is around the corner, and we’re happy to help you become more sovereign with your bitcoin. We hope you enjoy Faraday bags as one part of your security toolkit.

Learn more about Casa Premium here.

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