This paper gives a new approach for encrypting different types of files like text, image, audio, video etc. The file is considered as a binary string. It is first broken into blocks of equal sizes. Each block is then represented as a square matrix. Helical transposition is applied first, and then columnar transposition is done on the basis of session key. Session key is a 24 bit sequence which is used to generate decimal number sequence and accordingly columnar transposition is done. For decryption session key and anti-helical algorithm both are required.