Grayscale Text Watermarking

In an increasingly connected world, where information is easily spread through multiple channels and platforms, digital watermarking has been broadly investigated in authorship attribution and intellectual property protection of digital content. However, text contents pose many challenges due to a low capacity to embed a watermark. In this paper, we propose a new structural watermarking method for small pieces of text that may allow to hide upwards of 15 bits of watermark per character manipulating the underlying font grayscale values. The proposed method ensures length preservation and is robust to the copy and paste activities. Moreover, the method is able to embed a password-based watermark returning visually indistinguishable watermarked text.