NAME

       outguess - universal steganographic tool

SYNOPSIS

        outguess [OPTIONS] inputfile outputfile

DESCRIPTION

       OutGuess  is  a  universal  steganographic  tool that allows the insertion of hidden information into the
       redundant bits of data sources. The nature of the data source is irrelevant to the core of OutGuess.  The
       program  relies  on  data  specific  handlers  that will extract redundant bits and write them back after
       modification. Currently only the PPM, PNM, and JPEG image formats are supported, although OutGuess  could
       use any kind of data, as long as a handler were provided.

       OutGuess  uses  a generic iterator object to select which bits in the data should be modified. A seed can
       be used to modify the behavior of the iterator.  It is embedded in the data along with the  rest  of  the
       message.  By  altering  the  seed, OutGuess tries to find a sequence of bits that minimizes the number of
       changes in the data that have to be made.

       A bias is introduced that favors the modification of bits that were extracted  from  a  high  value,  and
       tries to avoid the modification of bits that were extracted from a low value.

       Additionally,  OutGuess  allows  for  the  hiding  of  two  distinct messages in the data, thus providing
       plausible deniability. It keeps track of the bits that have been modified previously and  locks  them.  A
       (23,12,7)  Golay  code  is  used  for  error correction to tolerate collisions on locked bits. Artificial
       errors are introduced to avoid modifying bits that have a high bias.

OPTIONS

       The following command line options, when specified as capital letters, indicate options  for  the  second
       message.

       -F [+-]
              Specifies  that  OutGuess  should  preserve  statistics based on frequency counts. As a result, no
              statistical test that is based on frequency counts will be able to detect steganographic  content.
              This option is set as on by default.

       -kK <key>
              Specify the secret key used to encrypt and hide the message in the provided data.

       -dD <datafile>
              Specify the filename containing a message to be hidden in the data.

       -sS <seed>
              Specify  the initial seed the iterator object uses for selecting bits in the redundant data. If no
              upper limit is specified, the iterator will use this seed without searching  for  a  more  optimal
              embedding.

       -iI <limit>
              Specify  the upper limit for finding an optimal iterator seed.  The maximum value for the limit is
              65535.

       -eE    Use error correction for data encoding and decoding.

       Other options that apply to the general execution of OutGuess:

       -r     Retrieve a message from a data object. If this  option  is  not  specified,  OutGuess  will  embed
              messages.

       -x <maxkeys>
              If the second key does not create an iterator object that is successful in embedding the data, the
              program will derive up to specified number of new keys.

       -p param
              Passes  a string as parameter to the destination data handler.  For the JPEG image format, this is
              the compression quality, it can take values between 75 and 100. The higher the  quality  the  more
              bits to hide a message in the data are available.

       -m     Mark pixels that have been modified.

       -t     Collect statistics about redundant bit usage. Repeated use increases output level.

       -h     Print a usage help text and exit.

       For  embedding messages, you need to specify a source and a destination filename. OutGuess determines the
       data format by the filename extension. If no filenames are specified OutGuess operates as  a  filter  and
       assumes the PPM data format.

EXAMPLES

       To embed the message hidden.txt into the monkey.jpg image:

           $ outguess -k "my secret pass phrase" -d hidden.txt monkey.jpg out.jpg

       And in the other direction:

           $ outguess -k "my secret pass phrase" -r out.jpg message.txt

       will retrieve the hidden message from the image.

       If you want to embed a second message, use:

           $ outguess -k "secret1" -d hide1.txt -E -K "secret2" -D hide2.txt monkey.jpg out.jpg

       OutGuess  will  first  embed hide1.txt and then hide2.txt on top of it, using error correcting codes. The
       second message hide2.txt can be retrieved with

           $ outguess -k "secret2" -e -r out.jpg message.txt

SEE ALSO

       cjpeg(1), djpeg(1), pnm(5), seek_script(1), stirmark(1)

AUTHOR

       OutGuess was originally developed by Niels Provos  <provos@citi.umich.edu>  and  is  maintained  by  some
       people.

       Currently,  source  code and newer versions are available at https://github.com/resurrecting-open-source-
       projects/outguess

outguess-0.4                                       02 Sep 2021                                       outguess(1)