convert ssh private keys to more secure format based on http://martin.kleppmann.com/2013/05/24/improving-security-of-ssh-private-keys.html

ssh_key_harden.sh

#!/usr/bin/env bash
NOW=$(date +"%Y%m%d%H%M%S")

if [ "$#" -eq 0 ];then
  echo "Usage $0 keyfile"
  echo "   or $0 -a           Convert all keys"
  exit
fi

function convert_file {
    echo "Converting $1"
    cp "$1" "$1-$NOW"
    openssl pkcs8 -topk8 -v2 des3 -in "$1-$NOW" -out "$1"
    chmod 600 "$1"
}

if [[ $1 == "-a" ]]; then
  for FILE in $(grep "PRIVATE KEY" ~/.ssh2/*); do
    convert_file $FILE_
  done
  echo "Check that the converted keys work; if yes, delete the old ones:"
  echo "$ rm ~/.ssh/*-$NOW"
  exit
else
  for FILE in $@; do
  if [[ -r $FILE ]]; then
    convert_file $FILE
  fi
done
fi