2011/8/24, luxInteg <[email protected]>:
> Greetings ,
>
> I would be grateful if someone could advise on the saving and retrieving
> of
> the random seed on a BLFS installation and if the random-seed cant be
> saved how does one generate one on boot from say time sources or whatever.
> (
> when the only writable area is /tmp)
Do you mean seed for /dev/urandom?
If so, you can use following script
# Get number of seconds since epoch (or date in any other format).
D=`date +%s`
# Get some (pseudo)random data (better to use /dev/random instead of
/dev/urandom but this may be dangerous if /dev/random does'nt have
sufficiently amount of random data).
R=`dd if=/dev/urandom count=64 bs=1 2>/dev/null`
# Calculate sha512 hash of concatenation of our two data. It will be
our random seed.
St=`echo -n "$R$D"|sha512sum -b|sed "s/ .*//"`
# Convert hash to string with hexes.
S=`echo $St|sed -r 's/([0-9a-f]{2})/\\\\x\1/g'`
# Write our seed in binary form to /dev/urandom.
echo -ne $S>/dev/urandom
So, you generate a seed which depends on current time and random data.
Michael Uleysky
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