I study lesson 2. In this lesson, I review some words that I learned later. My favorite study’s filed is cryptography. My last paper that present in ICCKE is a method for gray image encryption.This paper index in IEEE. Gray image is as a type of image that have one channel and it’s each pixel contains a value between 0 and 256 that indicate a level of darkness or brightness of each pixel. In abbreviate, our old picture that have no color, is a gray image. ..