Random Index Modulation Based Fragile Watermarking Scheme for Authenticating Colour Images

In this work we propose a random index modulation (RIM) based fragile watermarking scheme for authenticating RGB colour images. To thwart counterfeiting attacks, block-wise dependence neighbourhood is established, under the control of a secret key, and a content-dependent watermark is created by picking a certain number of bits from the dependence neighbourhood after scrambling its members. To minimise embedding distortion and to keep the location of the watermark secret, instead of embedding the watermark in the least significant bits, the proposed scheme embeds the watermark by associating a small set of indexes with the intensity range of the images in a random fashion under the control of the secret key and modulating the original pixels such that the indexes associated with the modulated / watermarked pixels are equal to the watermark bits to be embedded in the corresponding pixels.