The fatal attraction to the internet due to its flexibility for transferring digital content has

paved the way for certain copyright infringement issues. Any copyrighted material can

be easily exchanged over the internet without the consent of its rightful owner. Digital

watermarking, which is an application of data hiding technique, has been evolved as a

feasible solution to protect Digital Management Rights and content authentication and is

still a hot topic for researchers.

In classic watermarking techniques, the quality of the cover medium was given

the least importance in comparison with the secret data endorsed during the retrieval

process. But there are certain scenarios such as medical imagery where every bit of

information of cover medium is equally important as the secret code during the retrieval.

Reversible data hiding (RDH) addresses this problem and gives equal importance to the

cover as well as secret data.

Without mentioning the current status of Cloud Computing, the story of atrocities

in the digital communication field would be incomplete. As a resource of abundant

storage space and limitless software applications, Cloud computing is spreading its wings

over the world, day by day. Any entrepreneur can hire the above-mentioned services

offered by cloud storage providers by paying nominal charges and thereby able to reduce

their investment in hardware and software procurement required for computational jobs.

Apart from the initial investment in the infrastructure, the maintenance cost is also saved

since the entire machinery for computation and storage is maintained by the service

providers.

The objective of this book is to develop privacy preserving secure reversible data

hiding algorithms on grey images that can be either used for covert communication or

authentication. The algorithms should preserve not only the secrecy of the extra bits added

but also the secrecy of the host signal. They should be suitable to be adapted in the cloud

environment so that third party outsourcing is possible without leaking privacy. Usually,

in a cloud scenario, the client will be outsourcing storage and services from the cloud and

authentication of electronic data and its secrecy becomes a big issue.

This book presents high capacity image based reversible data hiding schemes which can

be evaluated both in the plaintext domain and encrypted domain. We put forth four

algorithms to preserve the authenticity as well as the privacy of the multimedia data

without fear of an intrusion. All these algorithms use encrypted versions of natural images

as a host image on which additional data will be embedded, and allow perfect reversibility

on retrieval of these natural images in noise-free conditions. Using these algorithms the

content owner could outsource an embedding algorithm from an untrusted third party in

a cloud environment without disclosing the cover to the embedder as it contains very

sensitive data. The owner encrypts the cover image to maintain the secrecy of the data

and embedder embeds the secret data on the encrypted image coefficients

homomorphically without knowing the host image. The owner could permit the

authorized people with a valid data hiding key for extracting the embedded secret data in

the encrypted domain but allow only the intended single recipient with the corresponding

decryption key to decode the marked data and reveal the cover.