RE: /dev/urandom uses uninit bytes, leaks user data

From: David Schwartz
Date: Mon Dec 17 2007 - 15:59:27 EST



> The bottom line: At a cost of at most three unpredictable branches
> (whether to clear the bytes in the last word with indices congruent
> to 1, 2, or 3 modulo 4), then the code can reduce the risk from something
> small but positive, to zero. This is very inexpensive insurance.

> John Reiser, jreiser@xxxxxxxxxxxx

Even if you're right, the change isn't free. You've simply presented
evidence of one non-zero benefit of it. You've given no ability to assess
the size of this benefit and no way to figure if it exceeds the cost. There
is also a non-zero *security* cost to this change.

DS


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