Introduction

With the growing popularity of digital Medias through the World Wide Web, intellectual property needs copyright protection, prevention of illegal copying and verification of content integrity. The new data hiding techniques need to be developed that satisfy the requirements of imperceptibility, robustness, capacity, or data hiding rate and security of the hidden data etc. At this juncture, the data hiding technique of hiding a host image in a cover image is a very efficient and secured way to send and share the host image in a confidential manner without the knowledge of the unauthorized accesses that something important or confidential has been sent.

Using the encoded image or cover image to send or share the image over WWW or via any secured communication over the electronic media is secured as it is usually imperceptible that the image is carrying a host image embedded within it and it can thus be shared without the concern of its loss or being gained access by unauthorized users because the host image is still secured and can be decoded only using the designed decoder. In our work we have been successful in developing dct calculator using vhdl which is a very important part of the sought hardware and having dct implements it.

A steganographic message (the plaintext) is often first encrypted by some traditional means, producing a cipher text. Then a cover text is modified in some way to contain the cipher text, resulting in stego text. For example, the letter size, spacing, typeface, or other characteristics of a cover text can be manipulated to carry the hidden message, only the recipient (who must know the technique used) can recover the message and then decrypt it. More simply it can be read as Science of hiding information.

Generally, a steganographic message will appear to be something else: a picture, and article, a shopping list, or some other message. This apparent message is the cover text. For instance, a message may be hidden by using invisible ink between the visible lines of innocuous documents.

The advantage of steganography over cryptography alone is that messages do not attract attention to themselves, to messengers, or to recipients. An unhidden coded message, no matter how unbreakable it is, will aruse suspicion and may in itself be incriminating, as in countries where encryption is illegal. Often , steganography and cryptography are used together to ensure security of the covered message.

A properly designed audio watermarking technology provides the means to secure the identities of a content‟s rights holders that calls for a technology which enables some secure auxiliary information, or watermark to travel with the content through any channel format or medium where the audio content‟s value remains secure, while preserving the integrity of the audio waveform. Subsequent to this process, the watermarked audio content becomes a message carrier regardless of the format of medium it lives on. Unlike sub-codes, encryption or audio compression, an audio watermark should not rely on any specific format. In order to travel along with the content it protects, the watermark must be carried by the content itself.

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