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Date: Thu, 8 Jun 2017 19:05:25 +0200
From: Marcel Holtmann <>
To: "Jason A. Donenfeld" <>
Cc: Theodore Ts'o <>,
 Linux Crypto Mailing List <>,
 LKML <>,,
 Greg Kroah-Hartman <>,
 "David S. Miller" <>,
 Eric Biggers <>,
 "Gustavo F. Padovan" <>,
 Johan Hedberg <>
Subject: Re: [PATCH v4 12/13] bluetooth/smp: ensure RNG is properly seeded
 before ECDH use

Hi Jason,

>> yes, there are plenty of commands needed before a controller becomes usable.
> That doesn't clearly address with precision what Ted was wondering.
> Specifically, the inquiry is: can you confirm with certainty whether
> or not all calls to get_random_bytes() in the bluetooth directory are
> *necessarily* going to come after a call to hci_power_on()?

on a powered down controller, you can not do any crypto. SMP is only during a connection and the RPAs are only generated when needed. So yes, doing this once in hci_power_on is plenty. However we might want to limit this to LE capable controllers since for BR/EDR only controllers this is not needed. For A2MP I need to check that we need the random numbers seeded there. However this hidden behind the high speed feature.



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