Recently, the BitLocker vulnerability became known – a hypothetical attacker could intercept encryption keys using an inexpensive Raspberry Pi Pico single-board computer costing less than $5. The example used was a ten-year-old laptop, which led to the assumption that modern models are not susceptible to the vulnerability. As it turned out, even modern laptops in 2023 running Windows 11 can still be hacked in a similar way.
The process of obtaining an encryption key has become a little more complicated over the past ten years, but the fundamental method has remained the same – intercepting data that is transmitted over unencrypted channels from the processor to a discrete TPM (Trusted Platform Module) chip. Security researcher Stu Kennedy created a GitHub page that lists laptop models with a confirmed vulnerability due to a dedicated TPM chip, including the Lenovo X1 Carbon, Dell Latitude E5470 and Microsoft Surface Pro 3 with TPM 2.0 chips. To carry out the attack, SPI, I2C or LPC buses are used.
It should be noted that this attack method only works if the attacker has physical access to the computer—it will not be possible to intercept the encryption key remotely. To protect yourself, you can choose additional measures, for example, use a password at startup or use a USB key. The BitLocker encryption key is stored on the TPM chip by default—you can change the preferred method in system settings. In addition, many modern Intel and AMD chips have a built-in TPM, which means that it is no longer possible to intercept its data when exchanged with the processor.