Formatted text document data hiding robust to printing, copying and scanning

A novel formatted text document data hiding algorithm, called inter-word space modulation (ISM) scheme, is proposed in which the spaces between neighboring words are modulated to hide data. In contrast to prior arts, this method does not require original documents for hidden data extraction. The hidden data are robust to printing, copying and scanning. Our experiments show that after printing, ten times of repeated copying, followed by scanning, the hidden data can still be extracted without a single bit error. It is expected that it can find wide applications for secure document processing, including digital notarization.