Messages in this thread | | | Date | Tue, 1 Jun 1999 13:26:09 -0700 (PDT) | From | David Whysong <> | Subject | Re: /dev/random and /dev/psaux: too much entropy assumed? |
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On Tue, 1 Jun 1999, C. Scott Ananian wrote: >On 1 Jun 1999, Florian Weimer wrote: > >> I would certainly like to end the thread after this, but I've got one >> further question: The implementation of /dev/random assumes that the >> output of the SHA-1 hash function is random for random (or almost random) >> input. Neither the people on sci.crypt nor I know of any analysis >> of SHA-1 in this direction (which doesn't prove anything of course). >> Are there any particular reasons why SHA-1 was chosen to supersede MD5? >> (It might indeed become practical to find collisions for MD5 soon, >> but this doesn't mean that MD5 is not suitable for applications like >> /dev/random.) > >Patent issues, I strongly suspect. And most of the applications for >/dev/random don't actually require 'uniformly distributed' output (which >is my guess as to what you mean by 'random'); rather they require >'unguessable' output. SHA-1, being a strong one-way function, provides >unguessable output. > --s
What? /dev/random not uniform? You've got to be kidding!
I use /dev/random a great deal in setting up large n-body simulations, which requires a very uniform distribution of numbers (huge monte-carlo methods, srand() probably isn't good enough). If it doesn't have 'uniformly distributed' output, it really isn't random and I'd like to know about that...
I did run some simple tests at one time and it looked uniform. But those were pretty silly tests (i.e. make a million numbers in [0,1] and plot a histogram).
Dave
David Whysong dwhysong@physics.ucsb.edu Astrophysics graduate student University of California, Santa Barbara My public PGP keys are on my web page - http://www.physics.ucsb.edu/~dwhysong DSS PGP Key 0x903F5BD6 : FE78 91FE 4508 106F 7C88 1706 B792 6995 903F 5BD6 D-H PGP key 0x5DAB0F91 : BC33 0F36 FCCD E72C 441F 663A 72ED 7FB7 5DAB 0F91
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