Hermetic Stego
Extracting a Data File
  1. Name output data file
  2. Enter stego key
  3. Specify image files containing the data
  4. Extract the data

By clicking on the following link you can download a ZIP file which contains the nine stego images mentioned below: 9_stego_images.zip (3,155,234 bytes).

After selecting the option to extract a data file you have to do two things:

  1. Decide on a name and location for the data file which is to be extracted (here we use the example of recovering the data file hidden in the previous section).
  2. Place the stego images in a folder (or tell the program where they are to be found).

a.  Name the output data file

Click on File for extracted data, locate the folder and enter the file name:

b.  Enter the stego key

If a stego key was used when hiding the file then it must be used when extracting the file. Clicking on Specify key brings up a window which allows you to enter a stego key:

stego key

c.  Specify the image files containing the data

Before the hidden data can be recovered the stego image files (which are copies of the original BMP image files with the data hidden within them) must first be assembled in a particular folder. There may be just one stego image, or there many be several, or many.

Click on Stego images folder to specify the folder containing the stego images. The stego image files should have the same names as they had when the data file was hidden in them.

In this example the images which are input to the operation are those which were written to the stego images folder in the example in the previous section. (You can follow this example in hands-on mode by downloading the nine stego images from this site; see Hermetic Stego in Trial Mode.)

The stego image files can be mixed with non-stego image files, or even with stego image files produced by hiding a file with a different stego key (but this is not recommended). Hermetic Stego uses the stego key which you give it (or the default stego key) to identify which files were used to hide a data file (with this stego key) and in which order they are to be used to extract the data.

d.  Extract the data

The button for this operation has now become active. Click on it to start the extraction. If you are about to overwrite a file a warning message will appear.

If all goes well then a report appears saying that the operation was successful.

Operation: Extract data
Data file: C:\_hst_test\output\lunecl.txt
Data file size: 1,186,737 bytes
Stego images folder:  C:\_hst_test\stego_images\
Data was successfully extracted from the following 9 images:
  check.bmp (2,406 bytes)
  palmen.bmp (827,454 bytes)
  dearsailors.bmp (807,506 bytes)
  threads.bmp (787,510 bytes)
  dog.bmp (589,878 bytes)
  puppy.bmp (589,878 bytes)
  sunset.bmp (589,878 bytes)
  view.bmp (197,686 bytes)
  bindu_sagar.bmp (197,686 bytes)

If you have checked the Open after extraction checkbox, and if the program is not a "sensitive" file (which includes files with extension 'exe', 'doc', 'scr', 'bat' and others) then the program will ask if you wish to open it (using the application associated with the file extension):

Sensitive files (including MS Word files) may contain executable code or macros, and such files are left to you to open in the usual way, exercising appropriate caution.

As stated above, by clicking on the following link you can download a ZIP file which contains these nine stego images: 9_stego_images.zip (3,155,234 bytes). Using the trial version of this software you can then follow the procedure described above, using now is the time for all good men as the stego key, to recover the hidden data file, lunecl.txt (this should be exactly 1,186,737 bytes in size).

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