New encryption vulnerability affects multiple bluetooth drivers

Avatar By Le Williams | 2 years ago

Lior Neumann and Eli Biham of the Israel Institute of Technology have discovered an encryption vulnerability in the Bluetooth firmware implementations of Apple, Broadcom, Intel, Qualcomm, and some Android smartphone makers.

Affecting both the “Secure Simple Pairing” and Bluetooth Low Energy “Secure Connections” pairing processes, the vulnerability has been identified with implementations of the above-mentioned companies failing to properly validate the public keys of the two devices that are paired with each other.

According to CERT/CC, which recently issued an advisory on this flaw, the secure pairing process works as follows:

“Bluetooth utilizes a device pairing mechanism based on elliptic-curve Diffie-Hellman (ECDH) key exchange to allow encrypted communication between devices. The ECDH key pair consists of a private and a public key, and the public keys are exchanged to produce a shared pairing key.

The devices must also agree on the elliptic curve parameters being used. Previous work on the “Invalid Curve Attack” showed that the ECDH parameters are not always validated before being used in computing the resulted shared key, which reduces attacker effort to obtain the private key of the device under attack if the implementation does not validate all of the parameters before computing the shared key.”

CERT added that without the elliptic curve validation, someone could not only decrypt and intercept the users’ messages, but they could also inject malicious messages.

According to the Bluetooth Special Interest Group (SIG), which develops the Bluetooth standard, the encryption bug is not seriously dangerous. SIG notes that an attacker would need to be present when two devices start the pairing process and could only take advantage of a narrow time window.