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Encoding Information in Steganographic Halftones

Event Date: March 1, 2012
Speaker: Dr Robert Ulichney
Speaker Affiliation: Hewlett Packard Labs
Sponsor: Communications, Networking, Signal & Image Processing
Time: 1:30 PM
Location: MSEE 239
Contact Name: Professor Jan Allebach
Contact Phone: (765) 494-3535
Contact Email:


While barcodes are a popular means for encoding information for printed matter, they add unsightly overt content.  A more attractive alternative is hiding the data in the halftone a graphic object, such as a logo or other image. We focus on the class of techniques that perform clustered-dot halftoning, as commonly used in electrophotographic printers.  The method takes as input any grayscale image and a payload of data and produces a bitonal clustered-dot halftone of that image with selected halftone clusters shifted to carry varying numbers of bits from the payload.  The resulting data-bearing steganographic halftone is referred to as a "Stegatone".

Because of the small size and large number of clustered-dot cells in printed halftones the bit density is quite high -- over 2000 bytes/square-inch.  Scans of test printed
stegatones from a number of printers support the robustness of the method with high recovery rates. Plans are underway to incorporate this feature in print drivers.  Applications include tracing the source of sensitive documents, passport security, and linking media to printed photos.

The talk will present the technology behind an open summer intern position with HP Labs.  Application can be made at for Job Number 704879*.*



Robert Ulichney* received a Ph.D. from MIT in electrical engineering and computer science. He was with Digital Equipment Corp. for several years where he focused on image and video implementations for both hard copy and display products. From 1998-2002 he was with Compaq's Cambridge Research Lab where he led a number of research efforts in video and image processing.  He has over 30 issued patents and several pending patents in these fields. Bob is currently a Distinguished Technologist with HP Labs.  His publications can be downloaded from