Digital authentication with digital and analog documents
First Claim
1. Apparatus which authenticates a digital representation of an object from which an analog form may be made, the apparatus comprising:
- an authenticator which uses first information in a first portion of the digital representation to produce first authentication information, the first information also being obtainable from a third portion of the analog form that is made from the first portion; and
an incorporator which incorporates the first authentication information in a second portion of the digital representation, the authentication information also being obtainable from a fourth portion of the analog form that is made from the second portion.
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Accused Products
Abstract
A watermark embedder transforms a media signal from its perceptual domain to frequency domain regions and embeds a hash of data from one frequency domain region into a watermark in another frequency domain region. Alternatively, it encodes instances of the same message into the frequency domain regions. To detect alteration of the media signal, a watermark decoder transforms a suspect signal into the frequency domain regions, extracts the watermark message from a first frequency domain region and compares it with a reference derived from another frequency domain region. The reference signal is either a hash computed from the other frequency domain region of the watermarked signal, or another instance of the same message embedded into the other frequency domain region. The decoder can be used to detect alteration of the signal, such as alteration that occurs with reproduction (printing, scanning, copying, D/A-A/D conversion, etc.), compression, cropping or swapping of media signal content, etc.
47 Citations
16 Claims
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1. Apparatus which authenticates a digital representation of an object from which an analog form may be made, the apparatus comprising:
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an authenticator which uses first information in a first portion of the digital representation to produce first authentication information, the first information also being obtainable from a third portion of the analog form that is made from the first portion; and
an incorporator which incorporates the first authentication information in a second portion of the digital representation, the authentication information also being obtainable from a fourth portion of the analog form that is made from the second portion. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. Apparatus which authenticates a digital representation of an object, the digital representation including frequency components and the apparatus comprising:
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an authenticator which uses first information in more significant frequency components of the components to produce first authentication information; and
an incorporator which incorporates the first authentication information into less significant frequency components of the components that do not overlap the more significant frequency components. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16)
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Specification