Cryptographic origin binding: How passkeys make phishing structurally impossible

Passkeys, based on the FIDO2/WebAuthn standards, offer a secure alternative to traditional passwords by employing asymmetric cryptography and enforcing cryptographic origin binding, thus making credential phishing mathematically unfeasible. Unlike passwords, which can be guessed, intercepted, or phished, passkeys are cryptographically tied to the domain they were created for, preventing their use on fraudulent sites. This is achieved through a dual-layer domain binding mechanism involving the Relying party ID and the origin recorded by the browser, both of which are embedded in signed data during authentication ceremonies. The authentication process involves generating unique asymmetric key pairs stored securely on authenticators, which can be platform-based, like Google Password Manager, or hardware devices like YubiKeys. These authenticators ensure that the private key never leaves the device, and any attempt to use the passkey outside its designated domain results in authentication failure. While passkeys significantly enhance security, they are not immune to threats such as browser compromise or session hijacking, and their recovery or backup poses challenges since they rely on cloud synchronization, which can expand the attack surface. The WebAuthn specification also supports extensions like prf and largeBlob, which enable additional cryptographic functionalities, potentially enhancing client-side cryptography. For developers, correctly implementing WebAuthn involves rigorous server-side verification, but services like WorkOS offer solutions that manage the complexities of the WebAuthn ceremony stack.