A Hidden Digital Text Watermarking Method Using Unicode Whitespace Replacement

The possibility of hiding information inside a digital medium is often referred to as watermarking or steganography. Since various solutions for image, video, and audio files exist, keeping control over text is challenging due to its limited possibilities. In this paper, we present a new digital text watermarking algorithm to hide a byte-encoded sequence inside an unformatted text. By substituting conventional whitespaces with a set of five similar-looking Unicode spaces, the cover text's structure and length stay untouched while remaining imperceptible to humans. We propose a software design and proof-of-concept multiplatform implementation with a downstream experimental evaluation for robustness, capacity, and visibility. Our findings indicate a stronger concealment and application robustness with limited embedding capacity compared to existing solutions utilizing zero-width spaces.