A novel fragile watermarking technique is proposed for hiding logo information into an image by tuning block pixels based on a bitmap parity checking approach. A secure key and a random number generator are used to hide the logo information in a secret, undetectable, and unambiguous way. The characteristics of the mean gray value and the bitmap in a block are exploited for performing the embedding work efficiently and for hiding a logo into an image imperceptibly. The logo can be extracted without referencing the original image. The proposed method is useful for authentication of original digital products. The extracted logo not only can be used to identify tampered locations in digital images but also can resist JPEG compression to a certain degree. Good experimental results have been conducted and resulting images show the feasibility and effectiveness of the proposed method
