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Cyber Risks · Trail of Bits Blog

The cryptography behind passkeys

Summary: Trail of Bits explains that passkeys are key pairs used to produce digital signatures, where the website stores only a public key and an identifier, and WebAuthn adds origin binding so a passkey created for bank.com cannot be used by a phishing site at fake-bank.com. The post notes that WebAuthn's Conformance section implies conforming websites, browsers, and authenticators are secure, but real attack scenarios remain, including compromised user devices, domain takeover or subdomain hijacking, and credential ID collisions that the spec only requires to be probabilistically unique.

What you should know: The post states that losing an authenticator generally means losing all passkeys it controls, with no hope of recovery for randomly generated key pairs, and that cloud-synced passkeys trade a larger attack surface for recoverability. It also warns that an attacker who registers a passkey with the same credential ID as a target victim could create authentication confusion, which is why websites should reject any registration whose credential ID already exists in the database.

Read the original at Trail of Bits Blog ↗

Topics
Data Breaches
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