Cracking a $2 million crypto wallet

In 2017, a 15-year-old hardware hacker in the UK named Saleem Rashid had developed a method to successfully unlock a Trezor wallet belonging to tech journalist Mark Frauenfelder and helped him free $30,000 in Bitcoin.Rashid found that when the Trezor wallet was turned on, it made a copy of the PIN and key that was stored in the wallet’s secured flash memory and placed the copy in RAM. A vulnerability in the wallet allowed him to put the wallet into firmware update mode and install his own unauthorized code on the device, which let him read the PIN and key where it was in RAM. This made it a risky technique for Grand to use; if he inadvertently erased the RAM before he could read the data, the key would be unrecoverable.In any case, Trezor had altered its wallets since then so that the PIN and key that got copied to RAM during boot-up got erased from RAM when the device was put into firmware update mode.So Grand looked instead to the method used in the 2018 conference talk that Reich had also examined previously. So they devised a technique dubbed “wallet.fail.” This attack used a fault-injection method — also known as glitching — to undermine security protecting the RAM and allow them to read the PIN and key when they were briefly in RAM.There are three levels of security available for the microcontroller used in Trezor wallets — RDP2, the most secure, which doesn’t let you read the RAM, and RDP1 and RDP0, which do. He found that in the version of firmware installed on Reich’s wallet, the key and PIN still got copied to RAM when the device was powered on. And because the key and PIN were merely copied to RAM at this point and not moved, unlike the wallet.fail scenario, this meant they still existed in flash if Grand inadvertently wiped the RAM. There will always be people with older unpatched versions of firmware on their wallets — like Reich — and he’s confident newer devices will still be vulnerable in different ways even if they’re patched.“It depends on the design, but with enough time and effort and resources, anything is hackable,” he notes.Trezor already fixed part of the problem Grand exploited in later versions of its firmware.