Security Enhanced Communication Scheme with Compression on Encrypted Cipher Block

The process of exchanging ideas or information between two persons or stations or devices is termed as communication. The information security has become one of the most significant problem in data communication. The intruder is an unwanted person who reads and changes the information while transmission occurs. So it becomes an inseparable problem in data communication. In order to address this problem, cryptography is used. Cryptography is the science of keeping message secret. It deals with transformations of a message into coded form by encryption at the sender (transmitting) side and recovery of original message by decryption at the receiver side. The classical way of transmitting data over an insecure channel is to first compress it and then encrypt. At the receiver, the received bit stream is first decrypted and then decompressed. But when the data is first compressed, there may be a problem of data loss and also if the sender is not able to perform the compression operation first then it will affect the smooth communication between the sender and the receiver. Inorder to overcome this problem, the existing technique is reversing such that the data will be first encrypted and then compressed without compromising the information secrecy. When the data is first encrypted with a secret key, then the data become secure and the sender can use the help of a third person to compress the data if the sender is not able to perform the compression operation first. The data security can be achieved using encryption and decryption algorithms. Here the encryption and decryption is performed using the Triple DES algorithm. The Triple DES algorithm is same as that of DES algorithm, in which the DES algorithm is applied three times to each block. The Run length encoding (RLE) method is used for data compression and decompression. The VHDL language is used for coding, synthesis can be done by means of Xilinx ISE and Model Sim can be used for simulation.