1. A method for authentication of JPEG compressed image data comprising the encoding steps of: a) deriving a hashing function from a first section of JPEG compressed image data such that any changes subsequently made to said section of data would be reflected in a different hashing function being derived therefrom producing an integrity checking number; b) encrypting said integrity checking number into a signature string; c) embedding said encrypted signature string into a second section of data; d) repeating steps A-D until the last section of image data is reached; and e) self-embedding the signature string corresponding to the very last data section into the data itself.