Electrical computers and digital processing systems: support – Multiple computer communication using cryptography – Particular communication authentication technique
Reexamination Certificate
1998-06-26
2001-07-31
Swann, Tod (Department: 2132)
Electrical computers and digital processing systems: support
Multiple computer communication using cryptography
Particular communication authentication technique
C713S179000, C713S181000, C380S030000
Reexamination Certificate
active
06269446
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to public key/private key authentication of images from digital cameras, and more particularly relates to public key/private key authentication of images from digital cameras with global positioning system (GPS) data.
2. Description of the Related Art
Digital cameras have become popular devices for producing high quality digital images of photographic scenes. In general, digital cameras create a digital image by exposure of a CCD sensor array to a photographic scene, followed by conversion of the CCD data to digital image data that is stored in the camera. Thereafter, the digital image data stored in the camera may be transferred to a personal computer or other more permanent storage for printout, viewing, transmission and the like.
One problem with digital image data, however, is the ease with which such data can be manipulated or changed, thereby creating a false representation of the original photographic scene. Such problems are particularly prevalent in certain fields such as forensics and legal or law enforcement fields, where it is essential to prove the authenticity of images. Because of the ease with which digital images may be altered so as to distort the appearance of the original photographic scene, proof of authenticity can often be difficult and sometimes impossible.
Conventional approaches to proving authenticity of digital images have involved the use of public key/private key digital signatures. One such conventional approach is described in U.S. Pat. No. 5,499,294 to Friedman. Friedman's approach involves the use of an embedded private key in a digital camera, with the private key being used to create a digital signature based on a message digest of the image data. Thereafter, a user wishing to authenticate-the image data obtains a public key that corresponds to the embedded private key. As is known in conventional public key/private key authentication, the public key and the private key correspond to each other such that only one public key can decrypt data encrypted with the private key, and vice-versa. Accordingly, through use of the public key, a user of Friedman's system is able to authenticate that image data has not been modified since when it was originally obtained by the digital camera.
One drawback of the Friedman system is its inability also to provide authentication of the photographic event, such as authentication of the time, date and position of the photographic scene involved, at least without visually distorting the digital image of the photographic scene. Specifically, Friedmin's system contemplates an arrangement in which GPS-derived position information is inserted as image data in a frame surrounding the photographic scene. However, such a frame detracts from the visual appearance of the image, making the image less pleasing to the viewer. Moreover, use of such data to authenticate the event is entirely manual, since the data is visual and must be inspected by a human operation. In addition, since the GPS-derived data is actually stored as image data, it is difficult to use the GPS-derived data for other purposes, such as sorting or cataloging.
SUMMARY OF INVENTION
It is therefore an object of the invention to authenticate events and images from digital cameras with GPS-derived data, by deriving a digital signature based on both coded GPS data and the image data, and by storing the digital signature in a header for a file with the image data.
Thus, in one aspect, the invention authenticates image data from digital cameras that have captured GPS-derived data as well as image data. A message digest is created for the image data, with the message digest being derived from the image data itself together with GPS-derived data such as time stamp data, location data. It is also preferable to include camera information data, such as serial number of the camera, size information, exposure information, and the like. The message digest is encrypted with a private key secure with the digital camera, and an image file is created together with a header that includes the private-key-encrypted message digest together with the unencrypted data that went into forming the message digest. For convenience, other information may also be stored in the header, such as a public key used to decrypt the encrypted message digest and which corresponds to the private key, and such as an identifier for the hashing function used to create the message digest.
The encrypted message digest forms a digital signature which verifies the authenticity of the image data, and which also verifies the authenticity of the event based on the GPS-derived data in the header. Moreover, because the GPS-derived data is stored in a header and not as part of the image data, the GPS-derived data can be used for other purposes such as sorting and cataloging, and the visual appearance of the image data is not distorted by the presence of unwanted GPS data.
In other aspects, the invention is verification of the authenticity of digital camera images having GPS-derived data. According to this aspect, to verify the authenticity of digital camera images, a public key is obtained, for example, from a trusted party. The public key is used to decrypt the private-key-encrypted message digest, so as to obtain a message digest for the picture. A trial message digest is calculated, using the same hashing function as was used by the digital camera to form the original message digest. The trial message digest is compared to the decrypted message digest for equality. If the two message digests agree, then the image data and the GPS-derived data are authenticated; conversely, if the two message digests do not agree, the image data and the GPS data cannot be trusted.
A additional feature of the invention involves the provision of a secure connection between a GPS receiver and a digital camera. Specifically, as can be appreciated from the foregoing explanation, one potentially weak link in the authentication/verification sequence is the connection between GPS information and the digital camera. If such a link is not secure, then it is possible for GPS data to be simulated to the digital camera, thereby resulting in forged images from the digital camera. To combat this possibility, a secure connection is provided between the GPS receiver and the digital camera, with the secured connection taking the form of either a public is key/private key encryption arrangement between the GPS receiver and the digital camera, or alternatively a GPS receiver that is built into the camera or resides on the same integrated circuit as the camera.
This brief summary has been provided so that the nature of the invention may be understood quickly. A more complete understanding of the invention can be obtained by reference to the following detailed description of the preferred embodiment thereof in connection with the attached drawings.
REFERENCES:
patent: 5005200 (1991-04-01), Fischer
patent: 5027401 (1991-06-01), Soltesz
patent: 5499294 (1996-03-01), Friedman
patent: 5579393 (1996-11-01), Conner et al.
patent: 5629981 (1997-05-01), Nerlikar
patent: 5659617 (1997-08-01), Fischer
patent: 5712914 (1998-01-01), Aucsmith et al.
patent: 5787172 (1998-07-01), Arnold
patent: 5799083 (1998-08-01), Brothers et al.
patent: 6105134 (2000-08-01), Pinder et al.
patent: 6111953 (2000-08-01), Walker et al.
“Introduction to Message Privacy”, <http:/www/pgp.com/privacy/intro-priv.cgi#mpriv-digsigs>, 6 pages, (visited Dec. 17, 1997).
Kohler Timothy L.
Schumacher Thomas
Canon Kabushiki Kaisha
Darrow Justin T.
Fitzpatrick ,Cella, Harper & Scinto
Swann Tod
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