Data Hiding In Hard-Copy Text Documents Robust To Print, Scan and Photocopy Operations
| Citation: | Varna, A.L.; Rane, S.; Vetro, A., "Data Hiding in Hard-Copy Text Documents Robust to Print, Scan, and Photocopy Operations", IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), April 2009 (ICASSP 2009) |
| MERL Report: | TR2009-020 |
| MERL Contacts: | Shantanu Rane, Anthony Vetro |
Characters with different embedded symbols at 300% magnification. The distance between the notches or bumps encodes a symbol.
This paper describes a method for hiding data inside printed text documents that is resilient to print/scan and photocopying operations. Using the principle of channel coding with side information, the embedder inserts a message into a text document while treating the content of the document as known interference. The data is embedded by making small changes to text characters before the document is printed. Using a simple correction-based detector in conjuncion with an error correction code, the hidden data can be extracted from a photocopy of the printed document. By enhancing the detector with an optical character recognition algorithm, the embedded data can be extracted even after multiple rounds of photocopying. Results from subjective tests show that the changes made by the embedding algorithm, while perceptible, are not obtrusive to a lay reader.
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