What are Passkeys?
A passkey is a new way to log in without typing a password. Instead of remembering complex passwords, you just use your fingerprint, face, or PIN the same way you unlock your phone. It's faster, safer, and way easier than passwords.
Think of it like: Using your house key instead of remembering a secret code. The key stays with you and can't be stolen by someone on the internet.
Passwords vs Passkeys
Traditional Passwords
What you deal with:
• Remember complex passwords
• Different password for each site
• Type it correctly every time
• Reset when you forget
• Can be stolen by hackers
Stored on the server!
With Passkeys
What you do:
↓
Use fingerprint or face ID
↓
Done! You're logged in.
✓ Nothing to remember
✓ Can't be phished
✓ Works across devices
✓ Never leaves your device
How Passkeys Work
sequenceDiagram
participant User
participant Device as Your Device
participant Website
Note over User,Website: First Time Setup (Registration)
User->>Website: Create account
Website->>Device: Request passkey creation
Note over Device: Generate key pair (public + private)
Device->>User: Authenticate with biometric
User->>Device: Fingerprint/Face ID verified
Device->>Website: Send public key only
Note over Device: Private key stored in secure hardware
Note over Website: Public key stored with account
Note over User,Website: Subsequent Login
User->>Website: Click login
Note over Website: Generate random challenge (nonce)
Website->>Device: Send unique challenge
Device->>User: Request biometric authentication
User->>Device: Fingerprint/Face ID verified
Note over Device: Sign challenge with private key
Device->>Website: Send signature
Note over Website: Verify signature using public key
Website->>User: Access granted!
Note over User,Website: Challenge is different every time
The website gets a "public key" that can't unlock anything by itself. Your device keeps the "private key" safe and uses it to prove you're you.
How Public Key Authentication Works
Passkeys use standard public-key cryptography with a challenge-response flow:
Step 1: Registration
During account setup, your device generates an asymmetric key pair. The public key is sent to the server and stored with your account. The private key stays in your device's secure hardware (like TPM or Secure Enclave) and never leaves.
Step 2: Challenge Request
On login, the server generates a random nonce (challenge) and sends it to your device. This prevents replay attacks since each challenge is unique.
Step 3: Sign Challenge
After biometric verification, your device uses the private key to sign the challenge. The signature is computed locally and sent back to the server. The private key itself never leaves the secure hardware.
Step 4: Verify Signature
The server uses your stored public key to verify the signature. If verification succeeds, it confirms you possess the corresponding private key without ever seeing it.
💡 Key point: This is standard asymmetric cryptography, but the private key is bound to your device's hardware and protected by biometrics. You get cryptographic security plus proof of physical presence.
Why Passkeys Are Better
Can't Be Phished
Unlike passwords, passkeys only work on the real website. Even if you click a fake link, the passkey won't work. The technology makes phishing impossible.
Super Fast
No typing, no forgotten passwords, no password resets. Just touch your fingerprint sensor or look at your camera and you're in. Takes less than a second.
Nothing to Steal
The secret never leaves your device. Even if a website gets hacked, there's nothing useful for hackers to steal. Your account stays safe.
Where You Can Use Passkeys
- Major Websites: Google, Apple, Microsoft, PayPal, Amazon, and many others already support passkeys.
- All Modern Devices: Works on iPhone, Android, Mac, Windows, and even Linux. Your phone can also log you into your computer.
- Synced Across Devices: Create a passkey on your phone and it works on your tablet and computer too. iCloud Keychain and Google Password Manager handle this automatically.
Common Questions
What if I lose my phone?
Passkeys sync across your devices through iCloud or Google. If you lose your phone, you can still log in from your other devices. Plus, websites usually let you set up multiple passkeys.
Can someone use my passkey if they steal my phone?
No. They'd need your fingerprint, face, or phone PIN to use the passkey. It's protected by the same security that locks your phone.
Are passkeys the same as two-factor authentication?
They're better. Passkeys combine both steps into one. You don't need passwords AND a second factor. The passkey is both things at once - something you have (your device) and something you are (your fingerprint).
