Reusing a Nonce, Key Pair in Encryption

Summary

In hostapd 2.10 and earlier, the PKEX code remains active even after a successful PKEX association. An attacker that successfully bootstrapped public keys with another entity using PKEX in the past, will be able to subvert a future bootstrapping by passively observing public keys, re-using the encrypting element Qi and subtracting it from the captured message M (X = M - Qi). This will result in the public ephemeral key X; the only element required to subvert the PKEX association.