Encrypted file using image steganography

corvette.sh

#!/bin/bash

# Author:   jamie.paton@googlmail.com

# COMMANDS

# create:  Args: <path to image file> <path to plain file>
#          Encrypts a file using the GPG utility, then zips it up and embeds
#          it into the image file

# open:    Args: <path to image file created by this script>
#          Extracts the file out of the image file using zip, then decrypts it

set -e
E_BADARGS=65
STORE_DIR=/tmp

if [ $# -lt 1 ]
then
  echo "Usage: `basename $0` <open|close> [args]"
  exit $E_BADARGS
fi

if [ $1 == "create" ]
then
  EXPECTED_ARGS=3

  if [ $# -ne $EXPECTED_ARGS ]
  then
    echo "Usage: `basename $0` create <path to image> <path to file>"
    exit $E_BADARGS
  fi

  if [ ! -f $2 ]
  then 
    echo "${2} does not exist"
    exit 1
  elif [ ! -f $3 ]
  then
    echo "${3} does not exist"
    exit 1
  fi

  outfile=$(basename $3).asc
  imgname=$(basename $2)
  ret=$(file $2 | grep -qi "image"; echo $?)
  if [ $ret -ne 0 ]
  then 
    echo "${2} is not a image file" && exit 1
  fi

  randzip=$RANDOM
  gpg -aci -o $STORE_DIR/$outfile $3
  cd $STORE_DIR
  zip $randzip.zip $outfile
  cd -
  rm -f $outfile
  cat $2 $STORE_DIR/$randzip.zip >> $STORE_DIR/"new-${imgname}"
  rm -f $STORE_DIR/$randzip.zip

  echo
  echo "Present delivered at ${STORE_DIR}/new-${imgname}"
  echo 


elif [ $1 == "open" ]
then
  if [ ! -f $2 ]
  then
    echo "${2} does not exist"
    exit 1
  else
    unzip -d $STORE_DIR $2 || true
    file=$(find $STORE_DIR/ -maxdepth 1 -type f \( -name "*.asc" -or -name "*.gpg" \))
    if [ -z $file ]
    then
      echo "Cannot find the unzipped file"
      exit 1
    else
      echo "Opening ${file}"
      gpg $file
    fi
  fi
else
  echo "Unknown operation: ${1}"
  exit 1
fi