Authentication and Error Resilience in Images Transmitted through Open Environment

Introduction

Nowadays, it is widely understood that data compression is not only essential to speed up the transmission rate but also to provide other gains like low storage. In order to counter data manipulations and tampering during transmission, the image authentication has turned out to be equally important. But the drawback of compressed data transmission is that the compressed data are susceptible to channel impairments.

The two common standards to compress and code images before transmission and storage are JPEG and JPEG2000. The JPEG standard is based on the discrete cosine transform (DCT) while JPEG2000 is based on the Wavelet transform. JPEG is the older standard and still widely used. The JPEG2000 is the newer standard. The original standard for digital images (IS 10918-1, popularly referred to as JPEG) was developed long time ago. Due to major advancement in computer technology and related research, it was decided by professional community that it is the timely need not only to find a standard that can make the digital image files as small as possible, but also find a new standard that can handle many more aspects. This was motivated by the fact that the JPEG2000 is better at compressing images (up to 20 per cent plus), and that it can allow an image to be retained without any distortion or loss. The communication and multimedia industry are shifting towards JPEG2000 standard for image transmission and storage. However, the JPEG2000 is still under improvements to reach the point where it could have its significant place in the world of imaging and telecommunications.

Data compression reduces the use of channel bandwidth; however compressed data are more vulnerable to channel noise. Therefore, the transmitted data must be resilient to channel noise and other impairments due to channel coding of binary bits (S. Khalid, 2009; L. Hanzo, et al, 2001; Y. Wang, Q. Zhu, 1998; Q. Memon, 2006). Several techniques have been proposed in the literature to address the problem of transmission errors by making transmitted data more robust to channel noise and to conceal corrupted data at the receiver. The authors (Mairal, C., Agueh, M., 2010) present a scalable scheme for robust JPEG 2000 images and video transmission to multiple wireless clients, using an adaptive bandwidth estimation tool. The objective seems to select suitable image layers and resolution for each wireless client, depending upon estimated bandwidth. The authors (Phadikar, A., Maity, S., 2010) propose JPEG200 compatible compressed domain algorithm using integer wavelet, and region-of-interest coding functionality. To find region-of-interest (ROI), threshold based image segmentation and morphological operations are used together to find ROI. Using simulation results, the authors claim that the scheme provides acceptable performance improvement with various lost blocks in ROI. In another research (Martinez-Ruiz, M., et al, 2010), the authors present the results of an initiative to transmit imagery content through a Link-16 tactical network using JPEG2000 compatible approach that involves wavelets to compress images. Specifically, the JPEG2000 code-stream is mapped into Link-16 free-text messages. The most important part of the JPEG2000 compressed image is transmitted through a more error resistant (and anti-jamming) Link-16 packed structure and the remaining of the image in less robust data structures but at higher data rates. The results claimed are preliminary and dependent on Link-16 network resources.