Extracting spread-spectrum hidden data from digital media

Technology Used: Dot Net

The problem of extracting blindly data embedded over a wide band in a spectrum (transform) domain of a digital medium image is considered. To develop a novel multicarrier/ signature iterative generalized least-squares (M-IGLS) core procedure to seek unknown data hidden in hosts via multicarrier spread-spectrum embedding. Neither the original host nor the embedding carriers are assumed available. Experimental studies on images show that the developed algorithm can achieve recovery probability of error close to what may be attained with known embedding carriers and host autocorrelation matrix.

 Covert communication or steganography, which literally means “covered writing” in Greek, is the process of hiding data under a cover medium (also referred to as host), such as image, video, or audio, to establish secret communication between trusting parties and conceal the existence of embedded data.
 While passive detection-only of the presence of embedded data is being intensively investigated in the past few years, active hidden data extraction is a relatively new branch of research.
 In blind extraction of SS embedded data, the unknown host acts as a source of interference/disturbance to the data to be recovered and, in a way, the problem parallels blind signal separation (BSS) applications as they arise in the fields of array processing, biomedical signal processing, and code-division multiple-access (CDMA) communication systems.
 Under the assumption that the embedded secret messages are independent identically distributed (i.i.d.) random sequences and independent to the cover host, independent component analysis (ICA) may be utilized to pursue hidden data extraction.
 An iterative generalized least squares (IGLS) procedure was developed to blindly recover unknown messages hidden in image hosts via SS embedding. The algorithm has low complexity and strong recovery performance.


 ICA-based BSS algorithms are not effective in the presence of correlated signal interference as is the case in SS multimedia embedding
 Degrade rapidly as the dimension of the carrier (signature) decreases relative to the message size.
 IGLS scheme is designed solely for single-carrier SS embedding where messages are hidden with one signature only and is not generalizable to the multi carrier case.

 Focused on the blind recovery of secret data hidden in medium hosts via multi-carrier/signature direct-sequence spread-spectrum (DS-SS) transform domain embedding.
 Neither the original host nor the embedding carriers (signatures or spreading sequences) are assumed known (fully blind data extraction).
 This blind hidden data extraction problem has also been referred to as “Watermarked content Only Attack” (WOA) in the watermarking security context.
 To develop a novel multi-carrier iterative generalized least squares (M-IGLS) algorithm for SS hidden data extraction that, to the best of the authors’ knowledge, appears for the first time in the broad communication theory and systems literature.


 Improved recovery performance
 The developed algorithm can be treated as a tool to test security robustness of SS data hiding schemes.

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