In recent years, as digital video technologies have been broadly used in TV,communication and multimedia. Security and privacy issues of the transmitted data have become an important concern in multimedia technology. Digital video stream is quite different from traditional textual data because interframe dependencies exist in digital video. Special digital video encryption algorithms are required because of their special characteristics, such as coding structure, large
amount of data and real-time constraints. This paper presents a real-time partial encryption to digital video technique based on
Symmetric Dynamic Dual (SDD) keys algorithm which is fast enough to meet the realtime requirements with high level of security.
This approach uses dual key for encryption with variable (dynamic) block bits size,each block bits size (3 or 4 bits ) are interpreted as an element of a finite field.. The first key is called control key determines the length of bits block (3 or 4 bits block) size to
encrypt, and the second key is used for encryption by using a equation:
Y = X. A+ BWhereX is bits block, AandB are the encryption keys.
The mathematical operations addition and multiplication in this equation are based on
mathematical theory of Galois field GF(2 ).
In this technique the I-frame (Intra-frame ) of the digital video scene is extracted
and decomposed the color picture into its three color channels:luma channel (Y) and
two chrominance channels Cb and Cr,with note that the frames of digital video is in
YCbCr color system, the SDD algorithm is applied to the Y channel.
The encryption algorithm achieves best timing results, and it provides high level of
security by its great resistant against brute force attacks, because it uses dual key and
dynamic block cipher, hence it will be very difficult to guess the key. To decrypt the
ciphertext with 128 bits, the attacker needs 8.86569157e+188 of possibilities of keys as
minimum and 7.91569097e+253 as maximum.