The post-quantum future of web privacy
The Cloudflare Blog · 软件开发
The highest priorities for the transition to post-quantum cryptography are the basic building blocks of authenticated key-agreement protocols such as TLS. Without these building blocks in place, secure communication on the Internet will not be possible once cryptographically relevant quantum computers come online. However, today we rely on quantum-vulnerable cryptography for much more than TLS. Privacy Pass is a protocol used by site operators like Cloudflare to help protect applications from abuse. One way we do this is by rate limiting individual clients so that no one client consumes too many of the site's resources. Normally this involves some combination of friction or loss of privacy for users: CAPTCHAs or other challenges to moderate traffic, along with accounts and fingerprinting to identify traffic.Privacy Pass was designed to avoid this tradeoff between friction and privacy. The basic idea is that a client gets issued a number of tokens , which they can redeem in exchange for access to the site. Crucially, each token is unlinkable to the client it was issued to, ensuring the client can use the site as they always had without sacrificing privacy. With 10 years of deployment experience under our belts — using Privacy Pass for applications such as privacy proxies (like iCloud Private Relay) and relays (like Privacy Gateway) — we, along with others , are collaborating to bring the next generation of this technology to the web. One of our goals is to develop more sophisticated tools for managing agentic traffic that would otherwise consume too many resources and degrade performance for human visitors. Another goal is to foster a more open ecosystem by making it easier for more types of clients to participate. Achieving these goals requires developing new capabilities beyond what Privacy Pass offers today. Given the trajectory, in this post we look at the prospects for post-quantum. In fact, we're in better shape than one might think. Privacy Pass still relies o