oysteikt/heimdal
0
0
Fork 0
Code Issues 5 Pull Requests Releases Activity

Reduce RNG false positive error rate

Browse Source
This commit is contained in:
Viktor Dukhovni
2013-10-17 00:29:51 -04:00
parent 146f5b72e6
commit 9a9ba1e197
1 changed files with 12 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
lib/hcrypto/test_rand.c
View File

@@ -178,12 +178,17 @@ main(int argc, char **argv)
* Normalizing by dividing by "n*p", we get a mean of 1 and
* a standard deviation of sqrt(q/n*p) = 1/sqrt(len).
*
* We tolerate 5-sigma events (1 in ~2 million builds will
* erroneously report RNG failure when the RNG is unbiased).
* A 5.33-sigma event happens 1 time in 10 million.
* A 5.73-sigma event happens 1 time in 100 million.
* A 6.11-sigma event happens 1 time in 1000 million.
*
* We tolerate 5.33-sigma events (we have 8 not entirely
* independent chances of skewed results) and want to fail
* with a good RNG less often than 1 time in million.
*/
for (bit = 0; bit < 8; bit++) {
res = slen * fabs(1.0 - 2 * (double)bits[bit] / len);
if (res > 5)
if (res > 5.33)
errx(1, "head%d vs tail%d: %.1f-sigma (%d of %d)",
(int)bit, (int)bit, res, bits[bit], len);
printf("head vs tails bit%d: %f-sigma\n", (int)bit, res);
@@ -195,12 +200,13 @@ main(int argc, char **argv)
* Normalizing by dividing by "n*p", we get a mean of 1 and
* a standard deviation of sqrt(q/n*p) ~ 16/sqrt(len).
*
* We tolerate 5-sigma events (1 in ~2 million builds will
* erroneously report RNG failure when the RNG is unbiased).
* We tolerate 5.73-sigma events (we have 256 not entirely
* independent chances of skewed results). Note, for example,
* a 5.2-sigma event was observed in ~5,000 runs.
*/
for (i = 0; i < 256; i++) {
res = (slen / 16) * fabs(1.0 - 256 * (double)bytes[i] / len);
if (res > 5)
if (res > 5.73)
errx(1, "byte %d: %.1f-sigma (%d of %d)",
(int) i, res, bytes[i], len);
printf("byte %d: %f-sigma\n", (int)i, res);