This paper presents a blind dual watermarking mechanism for digital color images in which invisible robust watermarks are embedded for copyright protection and fragile watermarks are embedded for image authentication. For the purpose of copyright protection, the first watermark is embedded using the discrete wavelet transform in YCbCr color space, and it can be extracted blindly without access to the host image. However, fragile watermarking is based on an improved least significant bits' replacement approach in RGB components for image authentication. The authenticity and integrity of a suspicious image can be verified blindly without the host image and the original watermark. The combination of robust and fragile watermarking makes the proposed mechanism suitable for protecting valuable original images. The experimental results indicated that the proposed watermarking mechanism can withstand various processing attacks and accurately locate the tampered area of an image.

Many researchers have studied reversible data hiding techniques in recent years and most have proposed reversible data hiding schemes that guarantee only that the original cover image can be reconstructed completely. Once the secret data are embedded in the compression domain and the receiver wants to store the cover image in a compression mode to save storage space, the receiver must extract the secret data, reconstruct the cover image, and compress the cover image again to generate compression codes. In this paper, we present a reversible data hiding scheme based on side match vector quantization (SMVQ) for digitally compressed images. With this scheme, the receiver only performs two steps to achieve the same goal: extract the secret data and reconstruct the original SMVQ compression codes. In terms of the size of the secret data, the visual quality, and the compression rate, experimental results show that the performance of our proposed scheme is better than those of other information hiding schemes for VQ-based and SMVQ-based compressed images. The experimental results further confirm the effectiveness and reversibility of the proposed scheme