Network security is a primary issue while exchanging the images over the system. Exceptional and dependable efforts to establish safety are required away and various usage of transmission of computerized images, for example, paytv, medical imaging frameworks, military image communications and confidential video conferences and so forth. With a specific end goal to defeat such security issues a few image encryption strategies have been proposed, however every one of them don't give security in all cases. Consequently need to grow increasingly secure picture encryption systems are dependably in need. In this paper a comprehensive approach is proposed where the image file is considered as a stream of bits. Images are assembling as grids of different variable sizes. Helical and Columnar transposition is used to transforms each grid into encrypted grid. By using public key algorithm like RSA, generated key is also wrapped up. We required a private key for decryption the anti-Helical transposition. With the help of decrypting the wrapped key with receiver’s private key we get session key. This method is provides the supports a variable size grid and secure variable length key.