[Python-checkins] cpython (3.4): Issue #21470: Do a better job seeding the random number generator

[raymond.hettinger]

http://hg.python.org/cpython/rev/c203df907092
changeset:   90692:c203df907092
branch:      3.4
parent:      90689:16d26391ec36
user:        Raymond Hettinger <python at rcn.com>
date:        Tue May 13 22:13:40 2014 -0700
summary:
  Issue #21470: Do a better job seeding the random number generator
to fully cover its state space.

files:
  Lib/random.py |  4 +++-
  Misc/NEWS     |  3 +++
  2 files changed, 6 insertions(+), 1 deletions(-)


diff --git a/Lib/random.py b/Lib/random.py
--- a/Lib/random.py
+++ b/Lib/random.py
@@ -105,7 +105,9 @@
 
         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
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -26,6 +26,9 @@
 - 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.
 

-- 
Repository URL: http://hg.python.org/cpython