Binomial transform based fragile watermarking for image authentication

In this paper, a novel Binomial transform based fragile watermarking technique has been proposed for color image authentication. Binomial transform (BT) is applied to convert each 2 × 2 sub-image block into transform domain in row major order. On average, two bits of authenticating watermark are fabricated on each transformed component starting from the least significant bit position (LSB-0). Inverse Binomial transform (IBT) is performed as post-embedding operation to convert each 2 × 2 transformed block back into the spatial domain. A delicate re-adjustment is performed on the first embedded component to keep the pixel components positive and less than or equal to 255 keeping the fabricated watermark unaltered. The watermark is extracted at the recipient end based on the reverse operation and is verified for authentication using a message digest. Experimental result ensures that the proposed technique obtain higher Payload and Peak Signal to Noise Ratio (PSNR) as compared to existing methods.