Image Steganography Using Discrete Cosine Transform (DCT) and Blowfish Algorithm

Steganography is one of the methods of secret communication that hides the existence of message so that a viewer cannot detect the transmission of message and hence cannot try to decrypt it. It is the process of embedding secret data in the cover image without significant changes to the cover image. A cryptography algorithm is used to convert the secret messages to an unreadable form before embedding. These algorithms keep the messages from stealing, destroying from unintended users on the internet and hence provide security. Cryptography was introduced for making data secure. But alone cryptography cannot provide a better security approach because the scrambled message is still available to the eavesdropper. There arises a need of data hiding. So the propose technique use a combination of steganography and cryptography for improving the security. The proposed technique use Discrete Cosine Transform (DCT) and Blowfish algorithm. The proposed method calculates LSB of each DC coefficient and replace with each bit of secret message. The proposed embedding method using DCT with LSB obtained better PSNR values. Blowfish algorithm is used for encryption and decryption of text message using a secret-key block cipher. This technique makes sure that the message has been encrypted before hiding it into a cover image. Blowfish is an improvement over DES, 3DES, etc designed to increase security and to improve performance. KeywordsSteganography, Cryptography ,DCT, LSB, PSNR, MSE.