Hidden data extraction

Patent Granted A product and process for extracting hidden data (2) from a stego-image (10') that has been subjected to scaling attacks are disclosed. The hidden data extraction method of the present invention retains the one-to-one mapping of the stego-image blocks to the corresponding blocks (18) in the scaled image. When the stego-image (10) is scaled down, the block size for extracting the hidden data (2) is reduced proportionally. When the stego-image (10) is scaled up, the block size for extracting the hidden data (2) is increased proportionally.