Multiple transform utilization and application for secure digital watermarking
Multiple transform utilization and applications for secure digital watermarking In one embodiment of the present invention, digital blocks in digital information to be protected are transformed into the frequency domain using a fast Fourier transform. A plurality of frequencies and associated amplitudes are identified for each of the transformed digital blocks and a subset of the identified amplitudes is selected for each of the digital blocks using a primary mask from a key. Message information is selected from a message using a transformation table generated with a convolution mask. The chosen message information is encoded into each of the transformed digital blocks by altering the selected amplitudes based on the selected message information.
1. A method for encoding a message and scale information into digital information corresponding to an audio signal, comprising:
(1) storing in digital memory of an encoder, digital information defining the message;
(2) receiving in said encoder, a digital audio signal block;
wherein said digital audio signal block is a digital representation of one of a set of temporally sequential segments of the audio signal;
(3) transforming, using said encoder and a transform, said digital audio signal block into the frequency domain, thereby defining a first set of amplitudes, wherein each one of said first set of amplitudes is associated with a corresponding one of a set of sequential frequencies ranges;
(4) identifying, using said encoder and said first set of amplitudes, an amplitude based frequency range subset of said corresponding set of sequential frequency ranges; and
(5) encoding, using said encoder and a primary mask of a key, at least some of said amplitude based frequency range subset, by altering the amplitude associated with the corresponding frequency range;
(6) receiving, in said encoder, a digital audio signal block, and wherein the digital audio signal block received in the encoder in step (6) corresponds to a next temporally sequential segment of the audio signal;
(7) repeating steps (3)-(5) on the digital audio signal bloc received in the encoder in step (6), followed by repeating step (6);
(8) repeating step (7) for the remainder of the digital audio signal blocks corresponding to the temporally sequential segments of the audio signal; and
(9) said encoder storing, in the key, said at least some of said amplitude based frequency range subset, and corresponding amplitudes, in association with one another; and
(10) said encoder storing, in the key, a digital representation of a sequence of the original audio signal.
2. The method of claim 1 wherein said sequence of the original audio signal comprises information defining the time duration of said sequence.
3. The method of claim 1 further comprising ( 11 ) storing the duration of said original audio signal in the key.
4. The method of claim 1 further comprising:
a decoder descaling an audio signal by matching a portion of the audio signal to said sequence of the original signal to determine a scale associated with said audio signal, and descaling the audio signal based upon the determined scale to generate a descaled audio signal; and
decoding the message from the descaled audio signal using the frequency ranges and corresponding amplitudes stored in the key.
5. The method of claim 1 further comprising a certification computer comprising computer memory storing the key in the computer memory; and certifying audio content by descaling and decoding based upon the sequence of the original audio signal stored in the key and the frequency ranges and corresponding amplitudes stored in the key.
6. The method of claim 1 further comprising said encoder tracking the sequential number of digital audio signal blocks it acquires by storing a window counter value in a window counter.
7. The method of claim 6 further comprising said encoder setting said window counter value to zero when said window counter value reaches a specified integer value.
8. The method of claim 1 further comprising said encoder encoding a start of message delimeter in said digital information.
9. A method for encoding a message and scale information into digital information corresponding to an image, comprising:
(1) storing, in digital memory of an encoder, digital information defining the message;
(2) receiving, in said encoder, a digital signal image block;
wherein said digital signal image block is a digital representation of one of a set of ordered segments of the image;
(3) transforming, using said encoder and a transform, said digital signal image block into the spatial frequency domain, thereby defining a fist set of amplitudes, wherein each one of said first set of amplitudes is associated with a corresponding one of a set of ordered frequency ranges;
(4) identifying, using said encoder and said first set of amplitudes, an amplitude based frequency range subset of said corresponding set of ordered frequency ranges;
(5) encoding, using said encoder and a primary mask of a key, at least some of said amplitude based frequency range subset, by altering the amplitude associated with the corresponding frequency range;
(6) receiving, in said encoder, a digital audio signal block;
wherein the digital image signal block received in the encoder in step (6) corresponds to next one of the ordered segments of the image;
(7) repeating steps (3)-(5) on the digital audio signal block received in the encoder in step (6), followed by repeating step (6);
(8) repeating step (7), for the remainder of the digital signal image blocks corresponding to the ordered segments of the image; and
(9) said encoder storing, in the key, said at least some of said amplitude based frequency range subset, and corresponding amplitudes, in association with one another; and
(10) said encoder storing, in the key, a digital representation of a portion the image.
10. The method of claim 9 wherein the digital representation of the image comprises information defining the spatial dimensions of the image.
11. The method of claim 9 further comprising ( 11 ) the encoder storing in the key, at least one spatial dimension of the digital representation of the image.
12. The method of claim 9 further comprising:
a decoder descaling an image signal by matching a portion of the image signal to said digital representation of said portion of the image, to determine a scale associated with said image signal, and descaling the image signal based upon the determined scaled to generate a descaled image signal; and
decoding the message from the descaled image signal using the frequency ranges and corresponding amplitudes stored in the key.
13. The method of claim 9 further comprising:
a certification computer comprising computer memory storing the key in the computer memory; and
said certification computer certifying image signals by:
descaling and decoding based upon the digital representation of the portion of the image sequence stored in the key and the frequency ranges and corresponding amplitudes stored in the key; and
determining whether the information decoded from the image signal corresponds to said message.
14. The method of claim 9 further comprising said encoder tracking the sequential number of digital signal image blocks it acquires by storing a window counter value in a window counter.
15. The method of claim 14 further comprising said encoder setting said window counter value to zero when said window counter value reaches a specified integer value.
16. The method of claim 9 further comprising said encoder encoding a start of message delimeter in said digital information.