초록 ▼

A watermarking scheme for images which includes techniques for inserting and extracting fragile watermarks in the frequency domain and for determining whether an image so watermarked has been tampered with. Watermark insertion is accomplished by embedding the bits of a digital signature of a hash fu

A watermarking scheme for images which includes techniques for inserting and extracting fragile watermarks in the frequency domain and for determining whether an image so watermarked has been tampered with. Watermark insertion is accomplished by embedding the bits of a digital signature of a hash function of the image in the frequency coefficients of the image. Tamper detection is accomplished generally as follows: the fragile watermark which was embedded during the watermark insertion process is extracted from the image; the hash function of the image is computed as in the insertion process; it is verified using a public key whether the extracted watermark is a valid signature of the hash value. If so, then there is assurance that the image has not been tampered with. Otherwise, there is reason to conclude that the image has been tampered with.

대표청구항 ▼

[ What is claimed is:] [1.] A method of watermarking a compressed digital image, comprising the steps of:partially decoding the compressed digital image to generate a plurality of data blocks, each block having a plurality of transform coefficients;determining whether to embed a watermark bit in eac

[ What is claimed is:] [1.] A method of watermarking a compressed digital image, comprising the steps of:partially decoding the compressed digital image to generate a plurality of data blocks, each block having a plurality of transform coefficients;determining whether to embed a watermark bit in each block based on one of the plurality of transform coefficients in that block and a number of watermark bits remaining to be embedded in the digital image;computing a watermark, having a plurality of bits, for the entire digital image by applying a digital signature algorithm and a secret key; andembedding a watermark bit in each block for which it was determined to do so in said determining step by setting the one of the plurality of transform coefficients in that block to match a corresponding bit of the computed watermark.