Document processing methods
Directional albedo of a particular article, such as an identity card, is measured and stored. When the article is later presented, it can be confirmed to be the same particular article by re-measuring the albedo function, and checking for correspondence against the earlier-stored data. The re-measuring can be performed through us of a handheld optical device, such as a camera-equipped cell phone. The albedo function can serve as random key data in a variety of cryptographic applications. The function can be changed during the life of the article. A variety of other features are also detailed.
1. In a method of compiling a database useful by an issuer of identity credentials, the method including storing—for each of plural issued credentials—a name of a credentialed person, and an image of such person, an improvement that includes also storing directional albedo information unique to said issued credential.
2. A method comprising the acts:
capturing image data from an identification document; and
by reference to directional albedo information previously known about said document, characterizing a position of said document in at least three dimensions, said characterizing act being performed by a hardware processor configured to perform such act.
3. The method of claim 2 that includes, by reference to steganographically encoded calibration data conveyed by said document, characterizing a position of said document in at least three dimensions.
4. The method of claim 2 wherein said dimensions comprise at least tip, tilt, and rotation angles.
5. A non-transitory computer readable medium containing instructions for configuring a processor programmed thereby to perform acts including:
receiving image data corresponding to an identification document; and
by reference to directional albedo information previously known about said document, characterizing a position of said document in at least three dimensions.