This work uses enhanced symmetric key encryption algorithm, in which same structure of encryption and decryption procedure algorithm is used. In conventional encryption methods the key for encryption and decryption is same and remain secret. The algorithm uses key generation method by random number in algorithm for increasing efficiency of algorithm. The algorithm use key size of 512 bits for providing better security and it also provide the concept of internal key generation at receiver end on the basis of 512 bits key which will entered by the sender. This internal key will store in the sender end database and send to the receiver end by other path for preventing brute force attack and other harmful attacks on security. This algorithm is more efficient for large data where existing algorithms provides efficient encryption and decryption only for 2MB data. This work provides better speed in comparison to existing algorithms for large size of files with less overhead.