Researchers have defeated a key protection against cryptocurrency theft with a series of attacks that transmit private keys out of digital wallets that are physically separated from the Internet and other networks.
Like most of the other attacks developed by Ben-Gurion University professor Mordechai Guri and his colleagues, the currency wallet exploits start with the already significant assumption that a device has already been thoroughly compromised by malware. Still, the research is significant because it shows that even when devices are airgapped—meaning they aren't connected to any other devices to prevent the leaking of highly sensitive data—attackers may still successfully exfiltrate the information. Past papers have defeated airgaps using a wide array of techniques, including electromagnetic emissions from USB devices, radio signals from a computer's video card, infrared capabilities in surveillance cameras, and sounds produced by hard drives.
On Monday, Guri published a new paper that applies the same exfiltration techniques to "cold wallets," which are not stored on devices connected to the Internet. The most effective techniques take only seconds to siphon a 256-bit Bitcoin key from a wallet running on an infected computer, even though the computer isn't connected to any network. Guri said the possibility of stealing keys that protect millions or billions of dollars is likely to take the covert exfiltration techniques out of the nation-state hacking realm they currently inhabit and possibly bring them into the mainstream.