A complete binary tree structure block cipher for real-time multimedia

We propose a new symmetric block cipher encryption which provides confidentiality to the multimedia while transmitting through the network. The encryption relies on two typical operations, substitution and transposition. A complete binary tree performs substitution and a 2-d array performs non-linear diffusion in the 2 stage of the encryption/decryption process. The first stage spreads out the bits of a block into a complete binary tree and performs randomized substitution based on a pseudo random permutation key P. The second stage lays out the bits from first stage into a square matrix and performs random shifting row/column wise in a circular fashion based on the key P. The encryption process consists of n rounds of identical transformations applied to the plaintext yield the ciphertext C. The proposed system is a novel non-conventional full encryption approach, which treats the entire multimedia bit stream as byte streams and uses the encryption scheme to encrypt the entire data stream. Thus the encrypted streamed data is transmitted by the sender and received and rendered in real-time by the receiver. The receiver can start playing back multimedia as soon as enough data has been received and stored in the receiver´s buffer. The performance of the proposed algorithm is compared with two symmetric encryption techniques namely AES and RC6. The experimental results show that there is only a few seconds of startup delay, i.e., the delay between the sender streaming the data and the client receiving playback. Thus the proposed system enables the real time or on demand distribution of audio, video and multimedia over the Internet. Hence the proposed algorithm achieves multimedia data confidentiality at low encryption effort and suitable for real-time multimedia communication applications.