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Groups > linux.kernel > #1681534
| From | Paul Koning <paulkoning@comcast.net> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: Antw: Re: [kernel-hardening] Re: [PATCH v4 06/13] iscsi: ensure RNG is seeded before use |
| Date | 2017-07-05 15:20 +0200 |
| Message-ID | <tZSnM-6FR-21@gated-at.bofh.it> (permalink) |
| References | (4 earlier) <tT7rz-5Uk-7@gated-at.bofh.it> <tTa65-7Jj-7@gated-at.bofh.it> <tTcUi-1gh-13@gated-at.bofh.it> <tTmTD-8lq-1@gated-at.bofh.it> <tZMLo-3av-15@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
> On Jul 5, 2017, at 3:08 AM, Ulrich Windl <Ulrich.Windl@rz.uni-regensburg.de> wrote: > >>>> Jeffrey Walton <noloader@gmail.com> schrieb am 17.06.2017 um 16:23 in Nachricht > <CAH8yC8nHX2r9cfQ0gNeJAUrgSfAS8V16dVHv35BRnLn-YprZCg@mail.gmail.com>: > > [...] >> But its not clear to me how to ensure uniqueness when its based on >> randomness from the generators. > > Even with a perfect random generator non-unique values are possible (that's why it's random). It's unlikely, but it can happen. The question is whether the probability of non-unique values from /dev/urandom is any higher than that for values read from /dev/random. One _might_ be able to predict the values from /dev/urandom. In the implementations I know, /dev/random and /dev/urandom are the same driver, the only difference is that when you read from /dev/random there's a check for the current entropy level. If you haven't fed enough entropy yet to the driver since startup, and you read /dev/urandom, you get a value that isn't sufficiently secure. If you have a properly constructed RNG, as soon as it's been fed enough entropy it is secure (at least for the next 2^64 bits or so). The notion of "using up entropy" is not meaningful for a good generator. See Bruce Schneier's "Yarrow" paper for the details. paul
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Antw: Re: [kernel-hardening] Re: [PATCH v4 06/13] iscsi: ensure RNG is seeded before use "Ulrich Windl" <Ulrich.Windl@rz.uni-regensburg.de> - 2017-07-05 09:20 +0200
Re: Antw: Re: [kernel-hardening] Re: [PATCH v4 06/13] iscsi: ensure RNG is seeded before use Paul Koning <paulkoning@comcast.net> - 2017-07-05 15:20 +0200
Re: Antw: Re: [kernel-hardening] Re: [PATCH v4 06/13] iscsi: ensure RNG is seeded before use Theodore Ts'o <tytso@mit.edu> - 2017-07-05 19:40 +0200
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