From: Jeff Epler <jepler@unpythonic.net>
To: Stephan Mueller <smueller@chronox.de>
Cc: "Theodore Ts'o" <tytso@mit.edu>,
linux-crypto@vger.kernel.org, lkml <linux-kernel@vger.kernel.org>
Subject: Re: [RFC][PATCH] Entropy generator with 100 kB/s throughput
Date: Sun, 10 Feb 2013 09:53:17 -0600 [thread overview]
Message-ID: <20130210155317.GA3070@unpythonic.net> (raw)
In-Reply-To: <5117969A.1080909@chronox.de>
OK, my original reading of the mixing code was not accurate. This time
around, I started with the original posted tarball and turned the use of
the CPU clock into a very simple and clearly bad "clock" that will
provide no entropy.
--- jitterentropy-0.1/jitterentropy.c 2013-02-08 15:22:22.000000000 -0600
+++ jitterentropy-0.1-me/jitterentropy.c 2013-02-10 09:45:07.000000000 -0600
@@ -270,12 +270,13 @@
typedef uint64_t __u64;
static int fips_enabled = 0;
-#define jitterentropy_schedule sched_yield()
+#define jitterentropy_schedule (0)
static inline void jitterentropy_get_nstime(__u64 *out)
{
- struct timespec time;
- if (clock_gettime(CLOCK_REALTIME, &time) == 0)
- *out = time.tv_nsec;
+ static __u64 t = 0;
+ const __u64 delta2 = 257;
+ static __u64 delta;
+ *out = (t += (delta += delta2));
}
/* note: these helper functions are shamelessly stolen from the kernel :-) */
This give a generator that has Entropy = 7.999907 bits per byte
and fails 6 in 10000 FIPS 140-2 tests. It also passes some (but not
all) dieharder tests.
Jeff
next prev parent reply other threads:[~2013-02-10 15:53 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-08 22:04 [RFC][PATCH] Entropy generator with 100 kB/s throughput Stephan Mueller
2013-02-09 18:06 ` Theodore Ts'o
2013-02-10 1:57 ` Jeff Epler
2013-02-10 12:46 ` Stephan Mueller
2013-02-10 15:53 ` Jeff Epler [this message]
2013-02-10 18:50 ` Theodore Ts'o
2013-02-10 19:27 ` Sandy Harris
2013-02-10 19:32 ` Stephan Mueller
2013-02-10 21:59 ` Sandy Harris
2013-02-11 0:05 ` Theodore Ts'o
2013-02-10 12:25 ` Stephan Mueller
2013-02-21 14:07 ` Phil Carmody
2013-02-21 14:17 ` Stephan Mueller
2013-02-21 17:46 ` Sandy Harris
2013-02-21 20:30 ` Theodore Ts'o
[not found] ` <CAFtRNNzcUpxT3R6ttUJ0c-7QTVRxbwRVq6bPqvkSL93vbstT4g@mail.gmail.com>
2013-02-22 11:14 ` Nick Kossifidis
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