  Digital watermarking is a technique of embedding pieces of information into
digital data such as text, audio, video, and still images that can be detected
or extracted later to show authentication about the data. Watermark is hidden
information in the image(s) and is so designed that it does not degrade/distort
the quality of the image and still keeps the information. Digital watermarking
is basically to protect ownership rights and to control of making illicit
copies of digital data. In this paper, we have discussed various watermarking
techniques and properties and have proposed a modified LSB technique. We have
implemented the proposed technique by following: 2-bits of 8-bit gray image is
replaced by luminance part, next 2-bits by red component, next 2-bits by green
component and next 2-bits by blue component of 32-bit image using secret key.
The advantage is that watermarking capacity has been increased and unaffected
by various attacks e.g. zero out LSB bits, cropping etc. Watermark image is
imperceptible in resultant image. We have tested this technique on several
images and found that it is quite satisfactory. This technique is secured as
unauthorized user can not extract the watermarked contents easily from the
original image and works well in adverse situations. We have implemented this
technique on platform java 1.5.0.
