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Discard first 3072 bytes of RC4 keystream, this is a bandaid

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that allows us to work on switching to a more modern PRNG.

Submitted by:	Steven Chamberlain <steven pyro eu org>
Approved by:	so
This commit is contained in:
Xin LI 2017-03-14 06:00:44 +00:00
parent 48fa9d448d
commit 91868665a9
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=315225
2 changed files with 3 additions and 3 deletions
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2
lib/libc/gen/arc4random.c
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@ -160,7 +160,7 @@ arc4_stir(void)
* Discard early keystream, as per recommendations in:
* "(Not So) Random Shuffles of RC4" by Ilya Mironov.
*/
for (i = 0; i < 1024; i++)
for (i = 0; i < 3072; i++)
(void)arc4_getbyte();
arc4_count = 1600000;
}

4
sys/libkern/arc4random.c
View File

@ -84,11 +84,11 @@ arc4_randomstir(struct arc4_s* arc4)
/*
* Throw away the first N words of output, as suggested in the
* paper "Weaknesses in the Key Scheduling Algorithm of RC4"
* by Fluher, Mantin, and Shamir. (N = 256 in our case.)
* by Fluher, Mantin, and Shamir. (N = 768 in our case.)
*
* http://dl.acm.org/citation.cfm?id=646557.694759
*/
for (n = 0; n < 256*4; n++)
for (n = 0; n < 768*4; n++)
arc4_randbyte(arc4);
mtx_unlock(&arc4->mtx);