For over four decades, passwords have been the fragile foundation of internet security. We have tried to patch their weaknesses with complex character rules, password managers, and SMS two-factor codes. Yet credential stuffing, database breaches, and Adversary-in-the-Middle (AitM) phishing kits continue to cause 80% of enterprise compromises. Here is how FIDO2 Passkeys mathematically neutralize credential theft.
The Asymmetric Cryptography Revolution
Unlike passwords, a Passkey is never a shared secret. When you create an account using WebAuthn:
- Your device (secure enclave, YubiKey, or phone) generates a unique Public/Private Key Pair using asymmetric curves (typically ECDSA on curve P-256 or Ed25519).
- The Public Key is sent to the server and stored openly in the database.
- The Private Key never leaves your physical hardware. It is sealed in hardware storage and cannot be exported or viewed.
Why Passkeys Cannot Be Phished
With traditional passwords or even authenticator app codes (TOTP), if an attacker lures you to a lookalike domain (e.g. secure-bank-login-fake.com), you type your password and 6-digit code, and the attacker immediately proxies those credentials to the real bank.
Passkeys prevent this by design through Origin Binding:
During authentication, the browser cryptographically binds the web origin domain (e.g. sendlyshare.com) into the authentication assertion signed by your private key. If the domain doesn't match the registered domain to the exact letter, the browser refuses to sign the challenge. An attacker's phishing site receives nothing.
Evaluating Legacy Password Health
While the world transitions to universal WebAuthn adoption, millions of legacy web services still require traditional passwords. For those accounts, testing your entropy and checking against breached credential corpora using tools like the Sendly Password Auditor ensures that weak passwords or exposed hashes are discovered before automated credential stuffing bots exploit them.