77 lines
2.5 KiB
Bash
Executable File
77 lines
2.5 KiB
Bash
Executable File
#!/bin/sh
|
|
# BlueShift: an experimental POSIX-compatible tool for
|
|
# high-density (1 byte per pixel) image-based steganography
|
|
# Depends on od, paste, dd, pr, awk, sed, ImageMagick and pngcrush
|
|
# Usage:
|
|
# - encoding: blueshift.sh e [cover image] [file to hide] [output PNG]
|
|
# - decoding: blueshift.sh d [container PNG] [output file]
|
|
# Created by Luxferre in 2026, released into public domain
|
|
|
|
# encode raw file as a netstring
|
|
to_netstring() {
|
|
printf '%d:' "$(cat "$1" | wc -c)"
|
|
cat "$1"
|
|
printf ','
|
|
}
|
|
|
|
# decode a raw file from a netstring (inside another file)
|
|
from_netstring() {
|
|
# get the container length
|
|
flen=$(head -n 1 "$1" | cut -f 1 -d :)
|
|
# skip the length itself and the : char
|
|
dd if="$1" of="$2" skip=$((${#flen} + 1)) bs=1 count=$flen
|
|
}
|
|
|
|
# convert PPM to plain RGB list (pixel per line)
|
|
ppm2rgb() {
|
|
tail -n +4 | sed 's/\s\+/\n/g' | pr -3ta
|
|
}
|
|
|
|
# for every input byte, print its 2-bit or 4-bit parts
|
|
# R: lsb 2 bits, G: msb 2 bits, B: hsb 4 bits
|
|
conv_input() {
|
|
to_netstring "$1" | od -An -tu1 -v -w1 | awk '{n=int($0);printf("%u\t%u\t%u\n",n%4,int(n/4)%4,int(n/16))}'
|
|
}
|
|
|
|
# stego_encode cover_image hidden_text out.png
|
|
stego_encode() {
|
|
coverfile="$(mktemp)"
|
|
infile="$(mktemp)"
|
|
tfile="$(mktemp)"
|
|
temp_ppm="$(mktemp)"
|
|
magick $1 -compress none ppm:$temp_ppm
|
|
cat $temp_ppm | head -n 3 > $tfile
|
|
cat $temp_ppm | ppm2rgb > $coverfile
|
|
conv_input "$2" > $infile
|
|
paste $coverfile $infile | awk '{if(NF>3)printf("%u %u %u\n", int(int($1)/4)*4+int($4), int(int($2)/4)*4+int($5), int(int($3)/16)*16+int($6));else print($0)}' >> $tfile
|
|
magick ppm:$tfile png:$3
|
|
pngcrush -ow $3
|
|
rm -f $coverfile $infile $temp_ppm $tfile
|
|
}
|
|
|
|
# stego_decode in.png out_file
|
|
stego_decode() {
|
|
temp_ppm="$(mktemp)"
|
|
tfile="$(mktemp)"
|
|
magick $1 -compress none ppm:- | ppm2rgb | awk '{printf("\\%03o", (int($3)%16)*16 + (int($2)%4)*4 + (int($1)%4))}' > $temp_ppm
|
|
printf "$(cat $temp_ppm)" > $tfile
|
|
from_netstring $tfile "$2"
|
|
rm -f $temp_ppm $tfile
|
|
}
|
|
|
|
# entry point
|
|
|
|
if [ "$1" = "e" ]; then
|
|
[ -z "$2" ] && echo 'No cover file specified! Exiting...' && exit 1
|
|
[ -z "$3" ] && echo 'No input file specified! Exiting...' && exit 1
|
|
[ -z "$4" ] && echo "No output file specified! Exiting..." && exit 1
|
|
stego_encode "$2" "$3" "$4"
|
|
elif [ "$1" = "d" ]; then
|
|
[ -z "$2" ] && echo 'No input file specified! Exiting...' && exit 1
|
|
[ -z "$3" ] && echo "No output file specified! Exiting..." && exit 1
|
|
stego_decode "$2" "$3"
|
|
else
|
|
echo 'Invalid mode! Use e for encoding or d for decoding'
|
|
fi
|
|
|