Patent ID: 8316425

Claim:
A method implemented in a data processing apparatus for authenticating a document, comprising: (a) processing a first area of a source document according to a first authentication level to generate first authentication data which represents an image of the first area at a first spatial resolution or first bit depth or first image compression ratio; (b) processing a second area of the source document according to a second authentication level to generate second authentication data which represents an image of the second area at a second spatial resolution or second bit depth or second image compression ratio, the second area being different from the first area, the second authentication level being different from the first authentication level, wherein the second spatial resolution or second bit depth or second image compression ratio is different from the first spatial resolution or first bit depth or first image compression ratio, respectively, and wherein the second authentication data generated for the second area according to the second authentication level has a smaller data amount than if the authentication data had been generated for the second area according to the first authentication level; (c) generating barcode data representing at least the first and second authentication data; and (d) carrying out at least one of: embedding the barcode data in the source document to generate a processed document, and printing the barcode data on a recording medium.