Secret,privateandconfidentialmessageusuallysentbyembeddingtheminacoveringmediasuchasdigitalcolorimage.Most steganographic methods used are suffering from the low level of security even if they used a private key for message hiding. In this paper we will introduce a method of message encoding-decoding, this method will use a digital color image as a source key to encode-decode secret messages, this method will provide a high level of security because of many reasons such as the huge size of the image which is used as a private key, this image is to be saved, and selected by the sender and the receiver without transmitting it over the internet. The same source image can be used to encode-decode various messages with any size even bigger than the image size.