Faraday Bag

What Is a Faraday Bag?

A Faraday bag is a portable enclosure constructed from conductive materials, typically metalized fabric, that creates a Faraday cage effect. Named after the nineteenth-century scientist Michael Faraday, these bags block electromagnetic radiation from passing through their walls, effectively isolating any device stored inside from all wireless communication.

When a hardware wallet or other electronic device is placed inside a properly constructed Faraday bag, it cannot send or receive radio signals. This means Bluetooth, Wi-Fi, NFC, RFID, and cellular signals are all blocked. The device becomes electromagnetically invisible.

Faraday bags have applications across many fields, from law enforcement evidence preservation to military communications security. In the Bitcoin world, they have become part of the self-custody security toolkit, used to protect hardware wallets from potential remote exploits and electromagnetic threats.

Why Bitcoin Holders Use Faraday Bags

The primary use case for Faraday bags in Bitcoin security is protecting hardware wallets from wireless attack vectors. Several scenarios motivate this practice.

First, some hardware wallets include Bluetooth or NFC capabilities for convenience. While these features are typically disabled when not in use, a Faraday bag provides an additional physical guarantee that no wireless communication can occur while the device is stored. This addresses concerns about firmware vulnerabilities that could potentially activate wireless interfaces without the user's knowledge.

Second, Faraday bags offer protection against electromagnetic pulses, whether from natural events like solar flares or theoretical deliberate attacks. While the probability of such events affecting a specific hardware wallet is low, the irreversible nature of Bitcoin private key loss makes some holders willing to defend against even low-probability threats.

Third, RFID skimming is a known attack vector for various electronic devices. While most hardware wallets do not use RFID, a Faraday bag eliminates this vector entirely as a precautionary measure.

The Self-Custody Security Stack

Faraday bags represent just one component of a comprehensive self-custody security setup. Serious self-custody practitioners typically maintain an elaborate security stack that includes hardware wallets stored in Faraday bags, metal seed phrase backups stored in fireproof safes, geographically distributed backup locations, passphrase-protected wallets, and detailed inheritance plans.

This security infrastructure is not trivial to maintain. Each additional layer adds complexity, and complexity itself can become a source of risk. A Faraday bag that is stored in the wrong location, a seed phrase backup that is improperly formatted, or an inheritance plan that is not kept current can each independently cause irreversible loss of funds.

Nick Szabo coined the concept of "trusted third parties as security holes," arguing that minimizing reliance on third parties improves security. This principle is foundational to Bitcoin and to the self-custody philosophy. However, Szabo also recognized that security is ultimately about managing trade-offs, not eliminating all risk.

The Complexity Problem in Self-Custody

For many Bitcoin holders, the security requirements of proper self-custody exceed their technical expertise or willingness to maintain ongoing operational security. This is not a criticism of self-custody. It is an honest acknowledgment that security systems are only as strong as their weakest component, and human error is frequently that weakest component.

Consider the operational requirements: hardware wallets must be kept updated, seed phrases must be stored securely but remain accessible, backup procedures must be tested, and the entire system must be documented for inheritance purposes. Add Faraday bags, metal seed backups, geographic distribution, and multisig setups, and the complexity becomes substantial.

Saifedean Ammous has observed that Bitcoin's role as a savings technology means it must be accessible to people across a wide range of technical sophistication. A security model that requires expertise in electromagnetic shielding, cryptographic key management, and physical operational security creates barriers to adoption that are at odds with Bitcoin's potential as universal sound money.

Multi-Institution Custody: An Alternative Approach

Onramp's Multi-Institution Custody (MIC) model offers a fundamentally different approach to Bitcoin security, one that achieves the goals of Faraday bags and complex self-custody setups through institutional infrastructure rather than individual operational security.

With MIC, private keys are distributed across three independent, regulated custodians: BitGo, Coinbase, and Anchor Watch. No single custodian holds enough keys to access client funds. This architecture provides several security properties that parallel or exceed those of a Faraday-bag-protected self-custody setup.

The electromagnetic security that a Faraday bag provides for a single hardware wallet is achieved in MIC through institutional-grade physical security at multiple independent data centers. The geographic distribution that self-custody practitioners create manually is built into the MIC architecture by design. The redundancy that multisig provides is enhanced by the independence and regulatory oversight of each custodian.

Critically, MIC eliminates the single point of human failure that plagues self-custody. There is no seed phrase to lose, no Faraday bag to misplace, and no firmware update to forget. Over $1 billion in assets are secured through this approach.

When Faraday Bags Make Sense

Faraday bags remain a sensible precaution for those who choose self-custody and use hardware wallets with wireless capabilities. They are inexpensive, simple to use, and provide genuine electromagnetic isolation. For small amounts of Bitcoin held in hardware wallets as spending money or for educational purposes, a Faraday bag is a reasonable addition to the security setup.

However, for significant holdings intended as long-term savings, the question is whether individual operational security, including Faraday bags, fireproof safes, and distributed backups, provides better protection than professional institutional custody with distributed key management.

Choosing the Right Security Model

Parker Lewis has written that Bitcoin adoption requires infrastructure that meets people where they are. Not everyone will become a security expert, and the growth of Bitcoin as sound money does not require them to. What it requires is trustworthy custody solutions that maintain the core properties that make Bitcoin valuable: verifiable scarcity, censorship resistance, and protection from counterparty risk.

Onramp's MIC model addresses counterparty risk through distribution rather than elimination. Rather than trusting a single entity, whether yourself or a custodian, the trust is distributed across multiple independent institutions. The result is security that does not depend on any individual's ability to properly maintain a Faraday bag, remember a passphrase, or execute a disaster recovery plan.

For Bitcoin holders evaluating their security options, the choice between a Faraday bag and institutional custody is not binary. Many Onramp clients maintain a small self-custody position while securing the majority of their holdings through Multi-Institution Custody. The right approach depends on the amount of Bitcoin, the holder's technical expertise, and their willingness to maintain ongoing operational security.

Frequently Asked Questions

Do I need a Faraday bag for my Bitcoin hardware wallet?

A Faraday bag provides electromagnetic isolation for hardware wallets with wireless capabilities, blocking potential remote attacks. However, for significant Bitcoin holdings, Onramp's Multi-Institution Custody offers more comprehensive security by distributing keys across BitGo, Coinbase, and Anchor Watch, eliminating the need for complex personal security measures.

Can a Faraday bag protect Bitcoin from EMP attacks?

Yes, a properly constructed Faraday bag blocks electromagnetic pulses from reaching a hardware wallet inside. However, this only protects a single device at a single location. Onramp's MIC distributes key material across multiple independent institutional data centers, providing geographic and electromagnetic redundancy by design.

What is the difference between a Faraday bag and Multi-Institution Custody for Bitcoin security?

A Faraday bag is a physical security tool that protects one hardware wallet from electromagnetic threats. Multi-Institution Custody distributes private keys across three independent custodians, providing comprehensive protection against physical, electronic, and human-error risks without requiring individual security expertise. Onramp secures over $1 billion through MIC.