Re: Wanted: Secure-delete utility for Linux

Kev (klmitch@MIT.EDU)
Wed, 23 Dec 1998 14:35:36 EST

> > Unfortunately the current /dev/random and /dev/urandom are very slow in
> > generating data. Therefore I would rather like a /dev/frandom for fast,
> > low quality randomness.
>
> Write a tiny program for the task, something like:
[snip]
> x =3D time(NULL);

This is already insecure; you can do better by reading 4 bytes from
/dev/{u,}random as appropriate. Also, I would probably use a
cryptographic hash function instead...if someone manages to recover
one of the random numbers you've generated with this PRNG, they can
recover the entire sequence; it's much more difficult to go back
with an appropriate hash function. You should also be able to do
other things that would hinder the forward prediction, as well...

-- 
Kevin L. Mitchell <klmitch@mit.edu>
-------------------------  -. .---- --.. ..- -..-  --------------------------
http://web.mit.edu/klmitch/www/               (PGP keys availiable from here)
    RSA AE87D37D/1024:  DE EA 1E 99 3F 2B F9 23  A0 D8 05 E0 6F BA B9 D2
    DSS ED0DB34E/1024: D9BF 0E74 FDCB 43F5 C597  878F 9455 EC24 ED0D B34E
    DH  2A2C31D4/2048: 1A77 4BA5 9E32 14AE 87DA  9FEC 7106 FC62 2A2C 31D4




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