Giovanni Under the Hood: Blue Spike Marries Cryptographic Techniques to Signal Processing
Giovanni Forensic Watermark Embedding Process
Giovanni's Forensic watermark - locatable only by the key holder who placed it - is embedded into signals in a four step process:
- Step 1: Key Generation
- Step 2: Watermark Message Generation
- Step 3: Signal Analysis
- Step 4: Watermark Placement
The rewards of this system are manifold. Giovanni places the watermarks in the most perceptually significant part of the signal, in large part so that attempts to remove the watermark will result in noticeable degradation of the signal. To be sure the watermark has been removed, a pirate would have to all but destroy the signal, gravely reducing if not totally obliterating its value.
The random placement of watermarks secures the protected object from hackers. They will be hard pressed to find the watermark, and if they do locate it at one place in the signal, they have no way to be sure they have found every place it has been planted. Hashing ensures that creators and distributors can detect tampering in a signal. In addition, the unique key used to plant the watermarks provides proof of the copyright holder's title to that signal.
What's more, the key management issues are reduced in number and complexity by the fact that the keys are associated with perceptible signals. Giovanni's encoding scheme can be a symmetric key system, using the same key to both encode the watermark and decode it and recover the watermark payload, or an asymmetric, public key watermark, which separates encoding from detection or decoding keys.
Instead of a cryptic block of incoherent text with no clue to what key unlocks it, watermarked information is identifiable. One key may be used per track, so locating the proper key for a watermarked track requires that the copyright holder to associate content with a key for which recovery of a particular or specific watermark. It may be that security can be assured by requiring detection of several independent watermark bits or messages in a particular order or even using different encoding schemes for different embedded bits. The combinations of particular cryptographic schemes matched with particular steganographic schemes is limited only by perception.
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