> QUESTION: But in case I would have to use a seed, how is this done?
> Especially with an UPDATED seed? This I do not know.
Advanced practical crypto implementation. What you do is, you store
some entropy on system shutdown to use at the next start together
with the best you can get at the start. On first start you are
screwed, buut for swap it is less critical. For exaple done by
GnuPG, in the form of $HOME/gnupg/random_seed.
Arno
SiSt:
I assume that I am close to the understanding of your point here, with this
excerpt from the urandom manual(?):
When a Linux system starts up without much operator interaction, the entropy
pool may be in a fairly predictable state. This reduces the actual
amount of noise in the entropy pool below the estimate. In order to
counteract this effect, it helps to carry entropy pool information across
shut-downs and start-ups. To do this, add the following lines to an
appropriate script which is run during the Linux system start-up sequence:
echo "Initializing random number generator..."
random_seed=/var/run/random-seed
# Carry a random seed from start-up to start-up
# Load and then save the whole entropy pool
if [ -f $random_seed ]; then
cat $random_seed >/dev/urandom
else
touch $random_seed
fi
chmod 600 $random_seed
poolfile=/proc/sys/kernel/random/poolsize
[ -r $poolfile ] && bytes=`cat $poolfile` || bytes=512
dd if=/dev/urandom of=$random_seed count=1 bs=$bytes
Also, add the following lines in an appropriate script which is run
during the Linux system shutdown:
# Carry a random seed from shut-down to start-up
# Save the whole entropy pool
echo "Saving random seed..."
random_seed=/var/run/random-seed
touch $random_seed
chmod 600 $random_seed
poolfile=/proc/sys/kernel/random/poolsize
[ -r $poolfile ] && bytes=`cat $poolfile` || bytes=512
dd if=/dev/urandom of=$random_seed count=1 bs=$bytes
--
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