You have to implement the Chi-square steganalysis technique to discover if there there is some message embedded in jpg image. A binary message is hidden into the LSB of the block-DCT transform. I can provide you original image and image with embedded message.
more info about chi-square steganalysis on this link (chapter Histogram-Based Attacks on LSB Embedding):
[url removed, login to view]~westfeld/publikationen/[url removed, login to view]
You have to write function in Matlab which will do Chi-square test