Secret San Francisco locations, coin tosses, and destroyed laptops were all part of the exchange's early key generation process
Coinbase once generated the keys to its cold storage inside Faraday-caged tents, set up at secret locations around San Francisco.
Start with the Faraday cage. Think of it as a mesh enclosure that stops electromagnetic signals from getting in or out.
Electronics leak faint signals while they run. In theory, a well-equipped attacker could capture those emissions and reconstruct sensitive data. Security researchers call these electromagnetic side-channel attacks.
Coinbase’s answer was to wrap the whole key generation process in a shield. The keys were created inside Faraday-caged tents, so whatever the machines emitted stayed inside the tent.
The tents also moved. Coinbase erected them at unpredictable locations in San Francisco, which made it much harder for anyone to plan surveillance ahead of time.
The hardware got the same treatment. Coinbase used two factory-sealed laptops for the job, one for generating keys and one for printing. One ran Linux. The other was a MacBook.
Both machines were air-gapped, meaning they never touched a network.
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Then came the coin toss. The laptops were chosen by flipping a coin. If nobody knows in advance which machine will be used, nobody can tamper with the right one beforehand.
Once the keys existed, the hardware stopped being an asset and became a liability. So Coinbase physically destroyed all of it.
That included the laptops and the printers, which were new for the ceremony. Printers tend to get overlooked, but they can store data from print jobs. Destroying them closes a door most people would never think to check.
The keys themselves were then split using Shamir’s secret sharing. Shamir’s scheme does that mathematically for cryptographic keys. In practice, it meant multiple participants had to cooperate to reconstruct a key, so no single insider could walk off with customer funds.
In later iterations of the process, Coinbase also brought in an independent auditor to confirm the ceremony ran the way it was supposed to.
The setup was not always this elaborate. At first, the company relied on USB drives and paper backups, stored in bank safe-deposit boxes.
Even with that simpler system, roughly 87% of customer funds were being held offline by late 2012.
For customers, the story is a reminder that cold storage is only as strong as the moment the keys are born. If a key is compromised at creation, every later safeguard protects something that is already exposed.
For anyone weighing where to hold assets, the practical takeaway is to ask how a custodian generates its keys, not just where it stores them.