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Linux's /dev/urandom and Python's os.urandom does not pass #10
Description
import os print( bin(int.from_bytes(os.urandom(1024),'big')))
does not pass Maurer test (09) and approx. Entropy test (12)
print( bin(int.from_bytes(open('/dev/urandom','rb').read(1024),'big'))) does not pass Maurer test (09) and randomly, does not pass approx. Entropy test (12) too
Activity
phmngcthanh commentedon Nov 26, 2022
I tried on Python 3.6.9 (default, Jun 29 2022, 11:45:57) [GCC 8.4.0] on linux, using Jetson Nano's Linux
I wonder, does it imply that both incompliance to NIST, or something else
ThexXTURBOXx commentedon Jun 28, 2023
Maurer's Test is only applicable for bit strings of length
>= 387840.As for the approximate entropy test, I think that with enough data (at least 10^6 or something), it might actually pass.
If your bit string is not long enough, the tests might "randomly" fail.
For even more reference, see section 4.3: https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-22r1a.pdf
fix: replace silent -1.0 return with descriptive error in Universal.py
stevenang commentedon Apr 5, 2026
This is expected behaviour —
os.urandom(1024)produces only 8,192 bits, well below the 387,840-bit minimum required by Maurer's Universal test. The test was silently returning(-1.0, False)which was confusing. This has been fixed in PR #33: the test now returns a clear error message instead. The Approximate Entropy result with short inputs may also be statistically unreliable — addressed by the minimum-length guards added in PR #34. Closing as addressed.