An Analysis of Attack Vectors Against FIDO2 Authentication
2026-04-22 • Cryptography and Security
Cryptography and Security
AI summaryⓘ
The authors studied a new login method called passkeys, which use special cryptographic keys to stop phishing attacks that trick people into giving away passwords. They explain how passkeys work and tested two new ways attackers might try to break them by controlling the device that stores the keys or spoofing websites. Their experiments show these attacks are hard to pull off and require a lot of effort. Overall, the authors found that passkeys do make it much tougher for attackers compared to normal passwords, supporting their claim to be resistant to phishing.
PhishingPasskeysFIDO2Asymmetric cryptographyAuthenticatorPublic keyPrivate keyCertificate authorityMan-in-the-middle attackBrowser security
Authors
Alexander Berladskyy, Andreas Aßmuth
Abstract
Phishing attacks remain one of the most prevalent threats to online security, with the Anti-Phishing Working Group reporting over 890,000 attacks in Q3 2025 alone. Traditional password-based authentication is particularly vulnerable to such attacks, prompting the development of more secure alternatives. This paper examines passkeys, also known as FIDO2, which claim to provide phishing-resistant authentication through asymmetric cryptography. In this approach, a private key is stored on a user's device, the authenticator, while the server stores the corresponding public key. During authentication, the server generates a challenge that the user signs with the private key; the server then verifies the signature and establishes a session. We present passkey workflows and review state-of-the-art attack vectors from related work alongside newly identified approaches. Two attacks are implemented and evaluated: the Infected Authenticator attack, which generates attacker-known keys on a corrupted authenticator, and the Authenticator Deception attack, which spoofs a target website by modifying the browser's certificate authority store, installing a valid certificate, and intercepting user traffic. An attacker relays a legitimate challenge from the real server to a user, who signs it, allowing the attacker to authenticate as the victim. Our results demonstrate that successful attacks on passkeys require substantial effort and resources. The claim that passkeys are phishing-resistant largely holds true, significantly raising the bar compared to traditional password-based authentication.