shamir's secret sharing with libgfshare-bin

gfshare_test.sh

#!/bin/sh

##
# Briefly demonstrate splitting a key with libgfshare-bin
# This breaks the key into M parts, N of which are needed for key recovery.

rm -vf key key.[2345] gfkey.*

dd if=/dev/urandom of=key bs=4k count=1
echo

sha256sum key

# default is 3-of-5
gfsplit key gfkey

for each in $(seq 2 5); do
  keyparts=$(ls gfkey.* | sort -R | head -3 | tr $'\n' ' ' ; echo)
  gfcombine -o key.$each $keyparts
  echo -n $(sha256sum key.$each) " "
  echo $keyparts
done