Perceptual image hashing maps an image to a short data string

applicable to image authentication

content based image retrieval

digital watermarking

etc. We propose a new image hashing algorithm using Harris corners and singular value decomposition. Critical feature points robust against gray level modification and image rotation are identified. A prescribed number of large singular values of the image blocks centered at the robust feature points are quantized to compress the data

which represent positions of the points and information of their neighborhood. The compressed data are then coded to generate the hash. The obtained hash is stable to visually insignificant changes due to normal image processing and JPEG coding

while sensitive to excessive changes and malicious tampering. Security of the hash is guaranteed by using secret keys.