Cloudflare Enables Post-Quantum Authentication for Origin Connections
Cloudflare has upgraded its Authenticated Origin Pulls and Custom Origin Trust Store to support post-quantum authentication using ML-DSA signatures, bolstering defenses against future quantum computing threats.
Cloudflare has announced a significant advancement in its post-quantum security roadmap by enabling post-quantum (PQ) authentication for connections between its network and customer origin servers. This new capability utilizes the Module-Lattice-Based Digital Signature Algorithm (ML-DSA) to secure these critical connections, protecting them from potential impersonation attacks that could be launched by adversaries armed with quantum computers.
The move represents a crucial step in Cloudflare's broader strategy to achieve full post-quantum security by 2029. While the company had previously focused on post-quantum encryption to safeguard data from future decryption, the accelerating pace of quantum computing development has prompted a shift to prioritize authentication mechanisms against quantum-powered impersonation threats. This upgrade specifically addresses the Cloudflare-to-origin connection, a distinct part of the overall web request lifecycle.
When a user visits a website proxied by Cloudflare, two primary connections are established: one from the visitor's browser to Cloudflare's edge, and a second from Cloudflare to the customer's origin server. Both connections require robust security against quantum threats. Cloudflare had previously introduced post-quantum encryption support for both segments in 2022 and 2023, respectively, and has seen substantial adoption.
The authentication aspect of the Cloudflare-to-origin connection presents unique challenges and opportunities. Unlike the visitor-to-Cloudflare connection, where Cloudflare acts as the server, in this scenario, Cloudflare is the client. This allows for the implementation of techniques like connection pooling, which can amortize the overhead of establishing secure connections over many requests. Furthermore, the existing trust relationship between Cloudflare and its customers enables the use of custom Public Key Infrastructures (PKIs) tailored to this specific use case, bypassing some of the constraints of the public WebPKI.
Cloudflare is now offering ML-DSA support for all FIPS 204 parameter sets (ML-DSA-44, ML-DSA-65, and ML-DSA-87) within its Custom Origin Trust Store (COTS) and Authenticated Origin Pulls (AOP) products. The company recommends ML-DSA-44 for most applications due to its optimal performance and NIST category 2 security strength. COTS allows customers to upload their own ML-DSA Certificate Authorities (CAs), ensuring Cloudflare trusts origin server certificates that chain to these custom CAs.
Authenticated Origin Pulls, a free feature available on all Cloudflare plans, allows customers to restrict requests to only those originating from Cloudflare's servers. This feature can now be configured to use ML-DSA client certificates for mutually authenticated TLS (mTLS) connections. This ensures that not only is the connection secure, but both Cloudflare and the origin server can verify each other's identity, preventing unauthorized access and resource abuse.
This deployment of post-quantum authentication via ML-DSA for the origin connection is being rolled out ahead of broader support in the public WebPKI. Cloudflare is also collaborating on standards for post-quantum certificates for the web (Merkle Tree Certificates or MTC), with initial deployments targeting 2027 for the visitor-to-Cloudflare connection. For customers who prefer to remain within the WebPKI framework, Cloudflare plans to add MTC support for the origin connection in the future.
The integration of ML-DSA signifies a proactive approach by Cloudflare to address the evolving threat landscape posed by quantum computing. By securing the crucial link between their network and customer origins with post-quantum authentication, Cloudflare is providing its users with enhanced protection against sophisticated impersonation attacks, moving closer to a quantum-resistant internet infrastructure.