Steganography using dynamic codes
DC CAFCFirst Claim
1. A method of processing a digital signal comprised of plural successive portions, said portions representing human-perceptible audio or image information, comprising:
- steganographically encoding first plural-bit auxiliary data in a first of said portions;
steganographically encoding second, different plural-bit auxiliary data in a second of said portions;
wherein at least one message bit in the first plural-bit data is encoded in a plurality of instances, and for each instance, the message bit is encoded in a groups of samples in the digital signal such that for each instance, the message bit is encoded differently according to a key.
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Abstract
An input content signal—representing audio or video—is steganographically encoded to hide plural-bit auxiliary data therein. The encoding operation changes over time, e.g., by using different “key” data for successive portions of the content signal. In some embodiments, the key data used in one portion of the signal is a function of auxiliary data decoded from a preceding portion. Consequently, to successfully decode the auxiliary data, the decoder must have successfully decoded a previous portion. In essence, decoding instructions are sent “on the fly” in such embodiments. In some embodiments, the auxiliary data is changed in temporally adjoining portions of the content signal—e.g., in successive frames of video or blocks of audio. In other embodiments, the key is changed less frequently, e.g., on a daily basis. External events may also trigger changing of the key data.
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Citations
36 Claims
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1. A method of processing a digital signal comprised of plural successive portions, said portions representing human-perceptible audio or image information, comprising:
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steganographically encoding first plural-bit auxiliary data in a first of said portions;
steganographically encoding second, different plural-bit auxiliary data in a second of said portions;
wherein at least one message bit in the first plural-bit data is encoded in a plurality of instances, and for each instance, the message bit is encoded in a groups of samples in the digital signal such that for each instance, the message bit is encoded differently according to a key. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of steganographically encoding auxiliary data within a signal comprised of plural successive portions, said portions representing human-perceptible audio or image information, characterized in that:
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the encoding proceeds with reference to key data;
the key data used for a first portion is different than key data used for a second portion; and
the key data used in the second portion is dependent on auxiliary data conveyed in the first portion.
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- 11. A method of steganographically decoding auxiliary data from a signal comprised of plural successive portions, said portions representing human-perceptible audio or image information, the steganographically decoding requiring use of reference data in order to discern the auxiliary data from the signal, characterized in that the reference data changes on the fly, depending on auxiliary data decoded from a preceding portion.
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21. In a method of steganographic decoding, an improvement comprising steganographically decoding data from a first portion of the encoded information that provides information necessary to steganographically decode a following portion of the encoded information.
- 22. In a method of steganographic encoding of content data with auxiliary data, an improvement comprising steganographically encoding data within a first portion of the content data that provides information necessary to steganographically decode a following portion of the content data.
Specification