图种

Sometimes you receive large files of small pictures of short videos, there is possiblity that it is a 图种.

Try rename it to .zip, .rar, .7z and on ubuntu unzip it in nautilus or terminal with uzip, unzip, urar, unrar (dont remember which is correct).

If it is with password, you can consider the GPU password cracker of me.

How to generate a 图种

Just use cat to append files.

cat image.jpg data.zip > hidden_image.jpg

Try download following file and rename file extension to .7z:

How to track If it is 图种

General technique is to get whether the image or video is too small compared to its size. For example when you download someting from Wallpaper engine.

binwalk hybrid.png
unzip hybrid.png

Technically just use ffmpeg, sox, vlc so on and some basis of media files, then you know whether it is too large:

For images:

identify -format "%[opaque]" test.png
identify -format "%[channels]" test.png
identify -format "%z" test.png
ffprobe -v quiet -show_entries stream=width,height -of csv=p=0 test.png # dimension of photo

Just calculate width * height * bytes per pixel, see if the number larger than your file size.

For videos,

 ffprobe -v quiet -show_format -show_streams test.mp4

See the bit_rate multiplied by duration for each stream (maybe one stream for audio and one stream for picture).

Steghide

Try steghide which will be less likely be affected by CDN compression,

for hiding,

steghide embed -cf mooeow.wav -ef secret.pdf    # hide pdf in wav

steghide embed -cf mooeow.wav -ef secret.pdf -p mewbies -sf mooeow_secret.wav   # hiding with password and output name

for decrypting:

steghide info mooeow_secret.wav -p mewbies

Steghide