With the development of network techniques the problem of network security becomes more and more important. The use of Word Wide Web has grown extremely in the past few years. Furthermore, many end users can easily use tools to synthesize and edit multimedia information. Thus, security has become one of the most significant problems for distributing new information technology. It is necessary to protect this information while communicated over insecure channels. Thus, a need exists for developing technology that will help protect the integrity of digital content and secure the intellectual property rights of owners. Cryptography and Steganography are the two major techniques for secret communication. The contents of secret message are scrambled in cryptography, where as in steganography the secret message is embedded into the cover medium. In this proposed system we developed high security model by combining cryptographic and Steganographic security. In cryptography we are using advanced encryption standard (AES) algorithm to encrypt secret message and then pixel value differencing (PVD) with K-bit least-significant-bit (LSB) substitution is used to hide encrypted message into truecolor RGB image. Our proposed model gives two tier security to secret data. Further our proposed method gives high embedding capacity and high quality stego images.