The subject of security has been around for a long time. Encryption is used to securely transmit data in open networks. A strong algorithm has been used for image security, this algorithm has added a sizable contribution to the field of data security and in particular, image security. This technique has the advantage of saving space by using the hiding efficiency method. Another benefit of this technique is its generality; it can be applied with any other algorithm to enhance its performance. This book opened a new window on digital images; their formats, processing and security as well as it provided a lot of knowledge about the encryption/decryption and steganography techniques and how to protect them from unauthorized access. The commonly used algorithms in industry and literature have been provided and how can use them in the encryption and decryption processes. Furthermore, the security measurement added a good knowledge and actual experience for users who want to distinguish between the properties of the available algorithms. This enabled users to quantify the differences between the different encryption/decryption algorithms.