Abstract: The authors propose an authentication scheme for JPEG images based on digital signature and semi-fragile watermarking to detect and locate the malicious manipulations made to an image and verify the ownership of the image. The algorithm uses the invariant of DCT coefficients before and after JPEG compression to embed the watermark related with the image in content. Since the authentication scheme is based on the security of the cryptographic hash function and public key algorithm, it is monodirectional and irreversible. The theoretical analysis and experimental results show that the proposed scheme has the desired property and good performance for image authentication.