SNOW
NAME
snow - whitespace steganography program
SYNOPSIS
snow [ -CQS ] [ -p passwd ] [ -l line-len ] [ -f file | -m
message ] [ infile [ outfile ]]
DESCRIPTION
snow is a program for concealing messages in text files by
appending tabs and spaces on the end of lines, and for
extracting messages from files containing hidden messages.
Tabs and spaces are invisible to most text viewers, hence
the steganographic nature of this encoding scheme.
The data is concealed in the text file by appending
sequences of up to 7 spaces, interspersed with tabs. This
usually allows 3 bits to be stored every 8 columns. An
alternative encoding scheme, using alternating spaces and
tabs to represent zeroes and ones, was rejected because,
although it used fewer bytes, it required more columns per
bit (4.5 vs 2.67).
The start of the data is indicated by an appended tab
character, which allows the insertion of mail and news
headers without corrupting the data.
snow provides rudimentary compression, using Huffman
tables optimised for English text. However, if the data is
not text, or if there is a lot of data, the use of the
built-in compression is not recommended, since an external
compression program such as compress or gzip will do a
much better job.
Encryption is also provided, using the ICE encryption
algorithm in 1-bit cipher-feedback (CFB) mode. Because of
ICE's arbitrary key size, passwords of any length up to
1170 characters are supported (since only 7 bits of each
character are used, keys up to 1024-bytes are supported).
If a message string or message file are specified on the
command-line, snow will attempt to conceal the message in
the file infile if specified, or standard input otherwise.
The resulting file will be written to outfile if speci-
fied, or standard output if not.
If no message string is provided, snow attempts to extract
a message from the input file. The result is written to
the output file or standard output.
OPTIONS
- C Compress the data if concealing, or uncompress it
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