Proposed in 1993 by Tirkel and Osborne.

Message is embedded in the least significant bit in a gray scale image.

There are two versions of the algorithm.

Version 1

Compress the 8-bit values for the color to 7-bit values, and embed information in the last bit.

Detection is done by knowing the key which is the pseudo random number generator that we use to find the pixels to embed the information.

Version 2

The watermark is added to the least significant bit and not replaced as in the earlier case.

Extraction is done by an auto correlation.