Inside a Swiss Nuclear Bunker Housing a Bitcoin Vault

Deep in the Swiss Alps lies a sophisticated nuclear bunker, now repurposed to secure Bitcoin holdings.

The notion may seem unusual, but a hidden vault within this mountain fortification protects a significant cache of Bitcoin. This facility employs cutting-edge multiparty computation (MPC) techniques to ensure the security of digital currencies.

With around 2 million Bitcoin believed to be inaccessible forever, the challenge of securely storing Bitcoin assets is a primary concern for holders today. While many enthusiasts recognize the phrase “not your keys, not your coins,” practical storage solutions can be elusive.

• Some opt to keep their Bitcoin on exchanges, accepting inherent risks.
• Others prefer moving their assets to cold storage for greater security.

For those seeking a more secure method, options like Xapo Bank offer the opportunity to leverage their specialized facilities, including underground bunkers, for Bitcoin storage.

The Bitcoin Vault: Switzerland’s Modern Fort Knox

Upon arrival, an Xapo Bank officer, Albert Rocca, instructed us to surrender our phones for security. Our devices were secured in a Faraday cage, effectively blocking any wireless signals and ensuring our locations could not be traced.

We landed at a small helicopter pad beside an unassuming military-style bunker door, which leads to a labyrinth of security.

Gaining entry to this vault involves several layers of security protocol, including:

• ID verification and thorough pat-downs
• Issuance of magnetic cards for controlled access
• A six-ton vault door designed to withstand extreme conditions

After passing through retinal scans and security codes, we moved deeper into the bunker, navigating through additional fortified barriers, including a man-trap with biometric technology. Each entrance was designed with multifaceted security measures to prevent unauthorized access.

At the heart of the vault is the MPC shard, critical for validating transactions related to Xapo Bank’s Bitcoin holdings. According to security expert Andrew Mannoukas, multiple redundancies are in place to thwart any potential attacks.

A Bunker Built for Security

The bunker serves more than just Bitcoin security; it houses various essential infrastructure and assets, acquired through a partnership with the Swiss Air Force in the 1980s. It features:

• Two one-megawatt diesel generators for backup power
• An advanced HEPA filtration system for air quality
• A cooling system utilizing an underground lake

Moreover, restricted areas within the bunker require specific clearance, equipped with stringent timed access protocols and ambient lighting for safe passage during authorized crossing periods.

Additional defenses include another six-ton vault door, complete with military-grade contingencies. The security measures showcase a marriage of traditional Swiss bunker architecture with modern technology.

Transitioning from Multisig to MPC Technology

In 2023, Xapo Bank transitioned from a multisig approach to employ MPC technology for securing its Bitcoin assets. Previously, staff managed daily transactions manually; however, this was replaced with advanced encryption techniques that eliminate the risk of revealing private keys.

Mannoukas oversaw this evolution, likening it to a collaborative cooking process where each chef contributes a secret ingredient without revealing it, creating a final dish without disclosing their individual contributions:

“This is similar to how MPC works, where each shard contributes their signature piece to form a complete authorization without any single party having full access to the private key.”

This method ensures that no one party has complete control, significantly enhancing security. The financial investment in the infrastructure and ongoing operational costs reflects Xapo Bank’s commitment to safeguarding client assets.