Giovanni Under the Hood: Blue Spike Marries Cryptographic Techniques to Signal Processing
Blue Spike, Inc. broke new ground in the late 1990s, developing software that used cryptographic keys to generate and embed steganographic digital watermarks into digitized signals like recorded music and digital images and even embedding in documents such as text. It was considered, by peers in industry and academe, an important achievement in that it employed the randomness of the traditional military-intelligence mode of cryptography (encoding data with a discrete key) to generate and place steganographic watermarks into digitized images, recorded music, video and information in general.
The scheme effected, at once, an innovative marriage of the cryptographic disciplines with signals processing and provided a unique mechanism for embedding secret, yet intelligible, data into signals. We bridged cryptography with perception, in one sense.
Blue Spike’s digital watermarking system, progeny of that breakthrough, is called Giovanni. Giovanni was developed to solve one big problem: how to embed title into a digitized object such as a song with a watermark in such a way that one could establish ownership of it. Embedding a digital watermark was a relatively straightforward task but providing a system that was undetectable, inaudible and provided proof of ownership presented myriad challenges.
It could not affect the quality of the signal to an extent that was audible to listeners. Audio being the most complicated of signal schemes to watermark, was the first target for our efforts. Since the scheme had to be undetectable – so that the watermark could not be located and removed – its locations had to be random. It had to survive over-writing – even with the same scheme – so that others could not claim the song or write their own title onto it.
These requirements were necessary in order for the marks that were generated by the scheme to have any standing among copyright holders pursuing control of their intellectual property. If there is a challenge over ownership, proofs must be conclusive. If, for example, a song is watermarked but no one can prove that the watermark is authentic, then what kind of standing can the watermark have?
To satisfy evidentiary conventions and the demands of audiophiles – and to deliver a system that would not be subject to cryptoanalytic short-cuts, Blue Spike turned to the disciplines of cryptography, steganography and psycho-acoustics to develop Giovanni. The synthesis of disciplines has been an extraordinary intellectual foray, thus far resulting in the awarding of some 33 US and international patents to the Company and its principals.
Blue Spike augmented traditional steganographic techniques by incorporating the signal carrier, such as recorded digitized sound, into the mathematical regime. The interaction of the signal and Giovanni’s mathematical algorithm are used to determine the placement of the watermark into the signal. The placement of the watermark is, in effect, determined by the character of the signal itself.
Blue Spike’s technology makes use of a psycho-acoustic or psycho-visual model, which identifies the most perceptually significant areas of the content for a watermark to be placed. This approach enables Giovanni’s watermarks to be embedded inaudibly, invisibly, and in such a way that, if removed, the content is likely to be damaged.
Giovanni’s Forensic Watermark – locatable only by the key holder who placed it – is embedded into signals in a four step process.