ASA-2019-00392 – AMD Secure Encrypted Virtualization (SEV): Platform DH key recovery via invalid curve attack

The SEV elliptic-curve (ECC) implementation was found to be vulnerable to an invalid curve attack. At launch-start command, an attacker can send small order ECC points not on the official NIST curves, and force the SEV firmware to multiply a small order point by the firmware’s private DH scalar. By collecting enough modular residues, an attacker can recover the complete PDH private key. With the PDH, an attacker can recover the session key and the VM’s launch secret. This breaks the confidentiality guarantees offered by SEV.