Passkeys Are Phishing-Resistant—But Not Magic: Where They Break in the Real World

🔐 Why Passkeys Matter

Traditional passwords are vulnerable — phishing, reuse, brute force, and leaked databases all make them brittle. The **BleepingComputer** article states that when passwords are stolen, attackers can easily reuse them across sites.

Passkeys shift that paradigm. Because the private key never leaves your device and is unique to each service, attacks like credential theft are ineffective without the device that holds the private key. This is why passkeys are quickly becoming a favored method for stronger, user-friendly authentication.

⚙️ How Passkeys Actually Work

Here’s the simplified cryptographic flow behind passkeys:

1. Your device generates a **private key** and a **public key** during registration.
2. The public key is sent to the service and stored.
3. When logging in, the service issues a “challenge,” which the device signs using the **private key**.
4. The service verifies the signature using the stored public key. Authentication succeeds without ever transmitting a secret.

This design ensures phishing sites or credential leaks can’t convincingly mimic the right domain or retrieve a reusable secret.

⚠️ Limits & Common Attack Vectors

While passkeys offer strong protections, they are not faultless. Some key limitations and attack vectors include:

• Compromised device: If malware or root control exists, the private key stored locally could be at risk.
• Browser or extension manipulation: Researchers have shown that malicious browser extensions or script injection can intercept registration flows, substituting passkeys without user realization.}
• Weak recovery flows / re-enrollment fraud: If the account’s fallback methods (SMS, email, help desk) are weak, attackers might enroll a new passkey illegitimately.
• Synced passkey dependency: Synced (cloud-backed) passkeys shift trust to the provider’s infrastructure — if that is compromised, attackers may replicate keys.
• Fallback authentication allowed: Services that still permit passwords, SMS, or less-secure fallback can allow attackers to bypass passkey usage altogether.

🛡 Defenses & Best Practices

1. Restrict browser extensions and apply managed policies: limit what scripts and add-ons can run.
2. Alert on new passkey enrollments, especially from new devices or across geographic anomalies.
3. Disable or harden fallback recovery methods (SMS, email) — require step-up verification for re-enrollment.
4. Use device posture checks: only allow passkey usage on devices meeting security policies (patch level, anti-malware, TPM integrity).
5. Prefer **device-bound passkeys** for privileged or high-risk accounts rather than fully synced variants.
6. User training: warn users to never click “add a security key” links from messages unless they initiated it.
7. Conduct periodic red-team / audit exercises focusing on passkey flows and recovery paths.

Also consider combining passkeys with additional security layers — e.g. requiring contextual risk checks (network, device) before authentication is granted.

Related Internal Reads

• Three Things You’ll Need Most If a Cyberattack Hits You
• How to Review and Revoke Connected Apps in 2025
• What to Do If a DDoS Attack Disrupts Your Online Service