Image Security through DWT &SVD based Watermarking and masking with Encryption

The rapid growth in the digital technology, image processing tools and communication revolution through Internet has made the reproduction of digitally created artifacts simple and within reach very easily. This new trend has several advantages in terms of flexibility, cost effectiveness, convenience etc., but at the same time, also raised some serious concerns in actual real life situation. Information security is an evolving phenomenon and no single technique seems sufficient enough to provide security of the images in the internet environment [1][12]. Encryption and digital watermarking techniques may be incorporated together in digital right management to achieve better security [2][3]. These two technologies are complimenting each other, and the increased security of the digital artifacts can be achieved by using benefits of the both. Encryption transforms the original digital contain into human unreadable format and watermarking leaves the digital object intact and recognizable with a permanent embedded tag of user specific information or logo embedded into it[7]. To hide the secret user specific information in the form of watermark it is encrypted using secret key based congruently generated pseudorandom number and then bitxoring to generate the encrypted watermark. The encrypted watermark is embedded in the host image using DWT and SVD based techniques and the watermarked image is further encrypted using key hashed based encryption techniques. This will prevent man in the middle attack by intercepting the watermarked image by the malicious attacker who may try to remove or distort the watermark and use it for malicious purpose. This technique makes the image human unreadable format and reduced in size while distribution and the user specific information is encrypted and permanently tagged with the host image through watermarking for authentication purpose [11]. The experimental results demonstrate the high robustness of the proposed algorithm to various image processing attacks like noise additions, rotations, cropping, filtering, compression etc. Keywords-watermarking, encryption, entropy, pseudorandom number, PSNR, normalized cross correlation (NCC), Normalized Hamming Distance (NHD))