There’s wide consensus among security experts that physical two-factor authentication keys provide the most effective protection against account takeovers. Research published today doesn’t change that, but it does show how malicious attackers with physical possession of a Google Titan key can clone it.

There are some steep hurdles to clear for an attack to be successful. A hacker would first have to steal a target’s account password and to also gain covert possession of the physical key for as many as 10 hours. The cloning also requires up to $12,000 worth of equipment, custom software, and an advanced background in electrical engineering and cryptography. That means the key cloning—were it ever to happen in the wild—would likely be done only by a nation-state pursuing its highest-value targets.