stegsnow

Extract [m]essage from file

$ stegsnow [path/to/file.txt]

$ stegsnow -C -p [password] [path/to/file.txt]

$ stegsnow -S -l 72 [path/to/file.txt]

$ stegsnow -m '[message]' [path/to/file.txt] [path/to/result.txt]

$ stegsnow -C -f '[path/to/message.txt]' [path/to/file.txt] [path/to/result.txt]

$ stegsnow -C -p [password] -m '[message]' [path/to/file.txt] [path/to/result.txt]

stegsnow [options] [in_file [out_file]]

-C
    Create a "clean" text file from input, removing trailing whitespace.

-e
    Extract hidden data from the input carrier text.

-f msg_file
    Specify a file to either read the message from (for hiding) or write the extracted message to.

-L length
    Set the maximum line length for the output when cleaning with -C.

-p password
    Provide a password for AES encryption or decryption of the hidden data.

-q
    Suppress all warning messages during operation.

-S
    Calculate and display the steganographic capacity of the input carrier file without performing embedding.

-s
    Display statistics about the embedding or extraction process, such as bytes hidden or extracted.

-V
    Display the version information of stegsnow.

-z
    Enable zlib compression for the message before embedding or decompression during extraction.

in_file
    The path to the input carrier text file from which data will be hidden or extracted. If omitted, input is read from stdin.

out_file
    The path to the output file where the modified carrier text (with hidden data) or cleaned text will be written. If omitted, output is written to stdout.

stegsnow is a steganography tool designed to hide data within ordinary ASCII text files. It accomplishes this by manipulating whitespace characters (spaces and tabs) at the end of lines. The core principle involves encoding each bit of the secret message using subtle variations in whitespace: a space might represent a '0' bit, a tab a '1' bit, or more complex schemes involving combinations or ordering of spaces and tabs.

This method makes the alterations virtually imperceptible to the human eye and often preserves the visual layout of the text. stegsnow supports both hiding (encoding) and extracting (decoding) information. To enhance security, it also offers features like data compression using zlib and strong encryption using AES in CBC mode, allowing users to conceal sensitive information. It's particularly useful for covert communication where the goal is to make the existence of a hidden message undetectable rather than just encrypting it. The carrier text, after embedding, remains a valid and readable text file, making detection challenging without specific knowledge or tools.

stegsnow relies entirely on trailing whitespace characters, which can be inadvertently removed by text editors, version control systems, or network transfers that normalize text files. This can lead to data loss or corruption of the hidden message. Its effectiveness is limited to ASCII text files, and it's not designed for embedding data in binary files or other media types. While the visual changes are minimal, advanced statistical analysis might be able to detect the presence of hidden data by analyzing the patterns of whitespace.

stegsnow primarily uses a scheme where different sequences of spaces and tabs at the end of lines represent binary bits. For example, a single space might represent a '0' bit, and a tab might represent a '1' bit. More complex schemes can involve sequences like 'space-tab' for '0' and 'tab-space' for '1'. This subtle encoding ensures that the visible text content remains unchanged, making detection difficult without specialized tools or knowledge of its operation. The choice of encoding varies based on the version and internal logic, maximizing hidden data capacity while minimizing visual impact.

stegsnow was developed by Matthew D. Thayer. It emerged as a specific solution for text steganography, focusing on the subtle manipulation of whitespace. Its development reflects the ongoing interest in creating covert communication channels that are resilient to detection. While other steganography tools might focus on image or audio files, stegsnow carved a niche for itself by leveraging the often-overlooked trailing whitespace in text documents, making it a simple yet effective tool for its intended purpose.

stegide(1), openssl(1), gzip(1)