STMicroelectronics ST33 TPM (ECDSA timing): Discrete TPM leaks ECDSA nonce data through timing, allowing private key

Impact

Discrete TPM leaks ECDSA nonce data through timing, allowing private key recovery from observed signatures. The discrete-chip half of TPM-FAIL - which matters because the usual answer to the fTPM flaw is 'use a real TPM', and this shows the real TPM had the same class of problem.

Who can reach it

Local attacker able to request signatures from the TPM, with accurate timing measurement.

What to do

TPM firmware update from ST, distributed through the platform OEM's BIOS package - per-node flash plus reboot, and vendor availability was patchy. Rotate any long-lived key the TPM produced. Where no update exists, treat that TPM's keys as software-grade rather than hardware-protected.

References