Re: [webauthn] Clarify the need for truly randomly generated challenges (#1856)

While I can understand the "temporarily stolen key" scenario, I do wonder how well that is protected against as is.

In particular, the availability of conditional mediation requires the use of challenges that are not only very long-lived, but also that can be generated without any prior authentication. It seems to me that if an attacker can gain temporary access to a key, and wishes to use it on a service with conditional mediation, then he can already make the service generate many valid challenges, that are kept current for a long time, and use them at his leisure.

Am I missing something about this? If I'm not, does that mean that services will need to choose between conditional mediation and higher security guarantees?

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Received on Monday, 20 February 2023 18:12:56 UTC