Abstract: Apparatus and methods are provided for embedding or encoding auxiliary signals into an analog host or cover signal. A replica of the cover signal or a portion of the cover signal in a particular domain (time, frequency or space) is generated according to a stego key specifying modification values to specified parameters of the cover signal. The replica signal is then modified by an auxiliary signal corresponding to the information to be embedded, and inserted back into the cover signal. Embedded auxiliary signals are extracted by generating replicas of received signals and correlating the replicas with the received signals.

Abstract: A tone detector includes at least one circuit (hereinafter “single phase reference matcher”) that not only performs a convolution of an input signal with a reference signal, but also compares the result of convolution with a threshold to determine if there is a match, and if so drives a signal active indicating that tone is present. If there is no match, another circuit (hereinafter “phase shifter”) delays the reference signal by a fraction (e.g. ⅛) of the measuring period, thereby to introduce a phase shift (e.g. &pgr;/8) between the input signal and the reference signal. The “single phase reference matcher” again performs the just-described operation, this time with a delayed reference signal, and repeats the operation as often as necessary (e.g. eight times) to cycle through the entire measuring period, thereby to ensure that tone (if present in the input signal) is detected irrespective of phase, during one of the operations.

Abstract: In the process of embedding watermark information in one-dimensional source data, first spread one-dimensional data x(t) is generated by subjecting one-dimensional source data s(t) to spectrum-spreading operation using a PN sequence g(t). This first spread one-dimensional data x(t) then undergoes a modified discrete cosine transformation. A specific frequency component value of the MDCT coefficients is modulated to provide association with the watermark information. The modulated frequency component then undergoes inverse transformation to generate second spread one-dimensional data x′(t). Then, using the same PN sequence in the spreading, the second spread one-dimensional data is subjected to spectrum-despreading to produce digitally watermarked one-dimensional data in which watermark data has been embedded.

Abstract: A technique for hiding of data, including watermarks, in human-perceptible sounds, that is, audio host data, is disclosed. In one embodiment a method comprises three steps. In the first step, data to be embedded is inputted. In the case of a watermark, this data is a unique signature, and may be a pseudo-noise (PN) code. In the case of hidden data to be embedded in the host data, this data is the hidden data itself, or the hidden data as spread against the frequency spectrum by a pseudo-noise (PN) code. In the second step, the inputted data is embedded within the host data, in accordance with a perceptual mask of the host data. The perceptual mask determines the optimal locations within the host data to insert the inputted data. In the case of sounds, these optimal locations are determined by reference to the human auditory system. In the third step, the host data, with the embedded data, is further masked by a non-frequency mask. In the case of audio data, the non-frequency mask is a temporal mask.