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Brute-Force can Breach Full Disk Encryption on Android Devices with Qualcomm Chips

by Felix Omondi
Brute-Force can Breach Full Disk Encryption on Android Devices with Qualcomm Chips

Either through a white hat or black hat hack, encrypted data on Android devices with Qualcomm chips can be accessible via brute-force hack. The would-be hacker can get the encryption keys protecting your encrypted data as long as a Qualcomm chipset powers the device.

This brute-force hack was demonstrated by a security researcher Gal Beniamini. He used vulnerabilities patched this year on Qualcomm’s implementation of the ARM CPU TrustZone. A hardware security module running its own kernel and Trusted Execution Environment, which is independent of the device’s main OS.

On Qualcomm processors, this Trusted Execution Environment is referred to as Qualcomm Secure Execution Environment (QSEE).  When you set a full-disk encryption on your Android device, the system randomly generates a decryption key known as the Device Encryption Key (DEK). Another security layer is added, where the DEK is further encrypted using an additional key obtained from your device’s PIN, Swipe Pattern, or Password.

Both Android and iOS attempts to bar would-be hackers from extracting the DEK, which would allow them to execute some brute-force hack and possibly guess the decryption password. In cases where there is an additional layer of protection such as software-enforced delays in-between failed attempts to guess the password.

That security layer is achieved through binding the DEK to the hardware of the given device by using an application known as the KeyMaster, which runs inside the Trusted Execution Environment.

However, in Android devices with Qualcomm, the chipset implementation uses a key readily available to the KeyMaster running inside the QSEE. Unlike iOS that binds the DEK to the device’s hardware using a key called the UID, which cannot be possibly extracted by software.

In other words, Android devices with Qualcomm chips, breaking into the QSEE will ultimately give hackers access to the KeyMaster key after which they can proceed to extract the DEK. Armed with that, they can run brute-force attacks on the device using power equipment like a server cluster designed to crack passwords.

The long story short; Android devices encryption is only as strong as the user’s Passwords, Swipe pattern, or PIN. Considering that the majority of users do not like setting up complex passwords, PINs, or Swipe Patterns, hackers work of guessing such security authentication are just that much easier.

Beniamini white hat hack was proof-of-concept about the vulnerability Android has, although they were patched in a January and May updates. However, the Android ecosystem devices receive updates much later, if at all. So many Android devices out there are as a matter of fact vulnerable, even when encrypted.

Beniamini further warns in a blog post, “Even on patched devices, if an attacker can obtain the encrypted disk image (e.g. by using forensic tools), they can then ‘downgrade’ the device to vulnerable version, extract the key by exploiting TrustZone, and use them to brute-force the encryption.”

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