Today, post-quantum cryptography (PQC) algorithms and hybrid PQC algorithms (classical and PQC algorithms combined) are accessible through open-source libraries and integrated into web browsers and other technologies. Traffic encrypted by PQC or hybrid PQC algorithms cannot be decrypted yet, making these algorithms vulnerable to misuse. To address these concerns, Palo Alto Networks firewalls now detect, block, and log the use of PQC and hybrid PQC algorithms in TLSv1.3 sessions. Successful detection, blocking, and logging of PQC and hybrid PQC algorithms depends on your SSL Decryption policy rules.

If SSL traffic matches an SSL Forward Proxy or SSL Inbound Inspection Decryption policy rule, the firewall prevents negotiation with PQC, hybrid PQC, and other unsupported algorithms. Specifically, the firewall removes these algorithms from the ClientHello, forcing the client to negotiate with classical algorithms. (For a list of supported cipher suites, see PAN-OS 11.1 Decryption Cipher Suites.) This enables continuous decryption and threat identification through deep packet inspection. If the client strictly negotiates PQC or hybrid PQC algorithms, the firewall drops the session. In the Decryption log for the dropped session, the error message states that the "client only supports post-quantum algorithms.” To see details of successful or unsuccessful TLS handshakes in the Decryption logs, enable both options in your Decryption policy rules.

If SSL traffic matches a “no-decrypt” Decryption policy rule or doesn’t match any Decryption policy rules, the firewall allows negotiation with PQC or hybrid PQC algorithms. However, details of sessions that negotiate these algorithms are available in Decryption logs only when session traffic matches a "no-decrypt" Decryption policy rule.

Additionally, new threat signatures offer additional visibility into the use of PQC and hybrid PQC algorithms in your network. These signatures monitor ServerHello responses and trigger alerts for SSL sessions that successfully negotiate with the most commonly known PQC and hybrid PQC algorithms. A Threat Prevention license is required to receive alerts.