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