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kernel: better nonce partitioning for chacha random number generator 

leave the block counter to chacha_encrypt() and increment the 96 bit
iv instead.
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cinap_lenrek 2016-09-11 03:18:48 +02:00
parent 10275ad6dd
commit 95c9f5bf37
1 changed files with 4 additions and 5 deletions
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9
sys/src/9/port/random.c
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@ -89,7 +89,6 @@ ulong
randomread(void *p, ulong n)
{
Chachastate c;
ulong b;
if(n == 0)
return 0;
@ -97,12 +96,12 @@ randomread(void *p, ulong n)
if(hwrandbuf != nil)
(*hwrandbuf)(p, n);
/* copy chacha state and advance block counter */
/* copy chacha state and increment iv */
qlock(rs);
c = *rs;
b = rs->input[12];
rs->input[12] += (n + ChachaBsize-1)/ChachaBsize;
if(rs->input[12] < b) rs->input[13]++;
if(++rs->input[13] == 0)
if(++rs->input[14] == 0)
++rs->input[15];
qunlock(rs);
/* encrypt the buffer, can fault */