System for authentication of JPEG image data
A system and method for authentication of JPEG image data enables the recipient to ascertain whether the received image file originated from a known identified source or whether the contents of the file have been altered in some fashion prior to receipt. A unique hashing function is derived from a first section of image data contained in the JPEG compressed image in such a way that any changes subsequently made to the first section of image data is reflected in a different hashing function being derived from a signature string is then embedded into a next section of the image data. Since the embedding of a previous section's integrity checking number is done without modifying the JPEG bit stream, any JPEG decoder can thereafter properly decode the image.
1. A system for enabling a recipient of an image file of JPEG image data to authenticate the image file of JPEG image data, the image file of JPEG image data having a first section and a second section, the first section containing a predetermined number of blocks of transformed coefficients and the second section containing a predetermined number of blocks of transformed coefficients, comprising:
a processor to receive an image file of JPEG image data;
said processor producing a hashing function from the first section of the received image file of JPEG image data;
said processor producing a first integrity checking value from the hashing function produced from the first section of the received image file of JPEG image data;
said processor identifying the second section of the received image file of JPEG image data, the second section having an encrypted signature string embedded in a least significant transmitted bit-plane of the second section of JPEG image data;
said processor extracting, from the least significant transmitted bit-plane of the second section of JPEG image data, the embedded encrypted signature string;
said processor decrypting the extracted encrypted signature string to recover a second integrity checking value;
said processor comparing the recovered second integrity checking value with the first integrity checking value;
said processor authenticating said first section of JPEG image data when the recovered second integrity checking value matches the first integrity checking value; and
said processor providing information to the recipient of the image file of JPEG image data that the image file of JPEG image data is authentic when each section of the image file of JPEG image data has been authenticated by comparing the recovered integrity checking value of each section with the produced integrity checking value of each section.