Last Updated on October 20, 2023
The program SNOW is used to conceal messages in ASCII text by appending whitespace to the end of lines. Because spaces and tabs are generally not visible in text viewers, the message is effectively hidden from casual observers. And if the built-in encryption is used, the message cannot be read even if it is detected.
SNOW exploits the Steganographic Nature Of Whitespace. Locating trailing whitespace in text is like finding a polar bear in a snowstorm.
The encoding scheme used by snow relies on the fact that spaces and tabs (known as whitespace), when appearing at the end of lines, are invisible when displayed in pretty well all text viewing programs. This allows messages to be hidden in ASCII text without affecting the text’s visual representation. And since trailing spaces and tabs occasionally occur naturally, their existence should not be sufficient to immediately alert an observer who stumbles across them.
The snow program runs in two modes – message concealment, and message extraction. During concealment, the following steps are taken.
Message -> optional compression -> optional encryption -> concealment in text
Extraction reverses the process.
Extract data from text -> optional decryption -> optional uncompression -> message
Features include:
- Compression scheme used by snow is a fairly rudimentary Huffman encoding scheme, where the tables are optimised for English text. This was chosen because the whitespace encoding scheme provides very limited storage space in some situations, and a compression algorithm with low overhead was needed.
- 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).
Website: darkside.com.au/snow
Support:
Developer: Matthew Kwan
License: Apache License v2.0
Snow is written in C. Learn C with our recommended free books and free tutorials.
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