Usage of gosteg:
  This application is used for PNG image steganography.  It can
optionally encrypt/decrypt the data using AES.  If no keyin file
is specified in encryption mode, a new key will be generated.
  An image can hold approximately three bits per pixel with this
steganography scheme.  There is a certain amount of overhead
for storing lengths, keys, etc.  Keep this in mind when choosing
an image size for embedding.

Options:
  --in       <file>   Input image (JPEG/PNG format)
  --out      <file>   Output image (PNG format)

  --embed    <file>   Embed data into the image from this file
  --extract  <file>   Extract data from the image to this file


  --crypt             Encrypt/decrypt the data (based on mode)
  --keyin    <file>   File containing Key, IV, and Next
  --keyout   key.dat  File to write new Key, IV, and Next
  --rotate            Rotate keys before encryption

Examples:

gosteg --in kitten.jpg --out kitten.png
  No steganography (just conversion to 64-bit color PNG)

gosteg --in kitten.jpg --out kitten.png --embed hideme.dat
  Embed hideme.dat into the PNG version of kitten.jpg and write it to kitten.png

gosteg --in kitten.jpg --out kitten.png --embed hideme.dat --crypt
  Same as above, except generate a new encryption key and write it to key.dat

gosteg --in kitten.jpg --out kitten.png --embed hideme.dat --crypt --keyin key.dat
  Same as above, except use the key from key.dat for encryption

gosteg --in kitten.png --out kitten.png --embed hideme.dat --crypt --keyin key.dat --rotate
  Same as above, except rotate the keys before use

gosteg --in kitten.png --extract hidden.dat
  Extract unencrypted data from kiten.png into hidden.dat

gosteg --in kitten.png --extract hidden.dat --crypt --keyin key.dat
  Extract data encrypted with key in key.dat into file hidden.dat