Encryption technique is an important method to ensure safe communication

but it has a shortcoming. Because the files encrypted are vulnerable to attackers

they may be destroyed.To solve the problem

the authors take advantages of the encryption technique and information-hiding technique

i.e. concealing the information encrypted into a carrier file. The authors adopts color image files being used in the Internet. If human eyes can not observe the diversifications of the carrier image before and after hiding

the method can be very safe.As far as the authors know

there are two kinds of encryption techniques. One is based on frequency region

such as expanding frequency hiding

DCT hiding and sub-wave hiding

etc. By these methods the information is concealed into the high frequency heft of the carrier image code

which can not be observed by human eyes. Generally speaking

not much data can be concealed into a carrier image. The other is based on space region

a typical method to conceal information in the least significance bits (LSB); however

due to their unsafety

they are not important to the carrier image. This paper provides a method that can create redundant space in a color image by color quantization and hiding information in the MSB of the image. The method is better than that in LSB since the MSB is very important to the visual effect of the image.