From: Raymond Hettinger <python@rcn.com>
Date: Wed, 14 May 2014 05:13:40 +0000 (-0700)
Subject: Issue #21470: Do a better job seeding the random number generator
X-Git-Tag: v3.5.0a1~1661^2
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=23042cda40bdab21db36a92d5d2655046207f947;p=python

Issue #21470: Do a better job seeding the random number generator
to fully cover its state space.
---

diff --git a/Lib/random.py b/Lib/random.py
index 808175ab4a..174e755a02 100644
--- a/Lib/random.py
+++ b/Lib/random.py
@@ -105,7 +105,9 @@ class Random(_random.Random):
 
         if a is None:
             try:
-                a = int.from_bytes(_urandom(32), 'big')
+                # Seed with enough bytes to span the 19937 bit
+                # state space for the Mersenne Twister
+                a = int.from_bytes(_urandom(2500), 'big')
             except NotImplementedError:
                 import time
                 a = int(time.time() * 256) # use fractional seconds
diff --git a/Misc/NEWS b/Misc/NEWS
index f85155e0bc..eff6573d94 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -26,6 +26,9 @@ Library
 - Issue #21396: Fix TextIOWrapper(..., write_through=True) to not force a
   flush() on the underlying binary stream.  Patch by akira.
 
+- Issue #21470: Do a better job seeding the random number generator by
+  using enough bytes to span the full state space of the Mersenne Twister.
+
 - Issue #21398: Fix an unicode error in the pydoc pager when the documentation
   contains characters not encodable to the stdout encoding.