Because of the need to ensure that only those eyes intended to view sensitive information can ever see this information, and to ensure that the information arrives unaltered, security systems have often been employed in computer systems for governments, militaries, corporations, and even individuals. Encryption schemes can be broken, but making them as hard as possible to break is the job of a good cipher designer. All what one can really do is make it very difficult for the codebreakers to decipher his cipher.The thesis in hand presents the implemented KBSA schemes which, provide privacy and confidentiality of multimedia data whether they are stored or communicated over insecure channels.To study secured communication over insecure channels, two main objectives are achieved which are: (i) Secrecy (or privacy),to prevent the unauthorized disclosure of data, and (ii) Authenticity (or integrity), to prevent the unauthorized modification of data through:· Generating the secret keys which will be used in the encryption and decryptionprocedures using the Blum-Blum-Shub generator and run them through a goodhash function before actually using them.· Implementing some cryptosystem schemes (KBSA) under the hash functionstechniques umbrella, that work as Message Authentication Codes (MAC), whichare easy to use, and be efficient for all keys then gathering them into a library(package) so, can be easily be applicable in real applications.·Stretching the limits of Cryptography by adding another layer of protection"Steganography" for hiding the information to reduce the chance of a messagebeing detected which works as a multilevel of security.·Compressing this information before transmitting to the other party.·Finally, encapsulating and activating these systems to be appropriate andfunctional in some real-world applications like: securing aerial imagestransmission, copyrights reserving and Internet security like (E-Commerce,E-Votingetc).Cryptography scrambles a message so it cannot be understood. Steganography hides the message so it cannot be seen. A message in ciphertext, for instance, might arouse suspicion on the part of the recipient while an "invisible" message created with steganographic methods will not. Unlike practical Cryptography, Steganography cannot be detected. The most prominent way of embedding information in multimedia data is the use of digital watermarking. Hiding information into image files by a way that can be indistinguishable by the naked eyes is presented. Also, Hidden copyright marks have been proposed as a solution for solving the illegal copying and proof of ownership problems in the context of software and audio files.Due to the mass storage of aerial and remote sensing images and their sensitive information used by decision makers, the need for a secured compression technique has become an important demand. So, Hybrid Fractal-RBC compression algorithm, which uses the benefits of both Fractal and the RBC image compression techniques, is presented. Thus, the merits of the two different approaches can be combined -Fractal at high compression ratios and the RBC at low compression ratios- and the overall coding efficiency can be improved.Three Main Results have been achieved:1. Combining Cryptography and Steganography to provide multilayer securitymechanism.2. Combining Fractal and Resampling Block Coding (RBC) image compressiontechniques to achieve the benefits of both.3. Real applications like: commercial & military.The KBSA techniques have been studied from the point of view of robustness,speed and several important properties, it was proved that extracting any information about the plaintext from the ciphertext is hard for any eavesdropper with computational resources due to multilevel securities that provides a computationally way to dramatically improve on the resistance exhaustive search attacks. It was found that the integrated KBSA algorithms are relatively accepted and robust, when they are compared with the standard encryption techniques. No one can guarantee 100％ security. But one can work toward 100％ risk acceptance.