Master’s Project Proposal
Secure communication of multimedia through encryption using matrix algorithm
Sandeep Chandrashekaregowda
January 28, 2014
Approved by:
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Advisor: Dr. Edward Chow
Date
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Committee Member: Dr. Rory Lewis
Date
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Committee Member: Dr. Jia Rao
Date
Table of content
1
Introduction .......................................................................................................................................... 1
1.1
2
Background ................................................................................................................................... 1
Proposed Project ................................................................................................................................... 2
2.1
Flexibility to perform selective encryption: .................................................................................. 2
2.2
Algorithm ...................................................................................................................................... 3
2.2.1
2.3
Summary of Multimedia Encryption ............................................................................................. 5
2.4
MP4 ............................................................................................................................................... 5
2.4.1
3
Matrix Encryption Algorithm ................................................................................................ 4
Frames................................................................................................................................... 6
Project plan ........................................................................................................................................... 7
3.1
Schedule ........................................................................................................................................ 7
4
Deliverables........................................................................................................................................... 7
5
References ............................................................................................................................................ 7
1 INTRODUCTION
In 1995 Meyer and Gadegast introduced the encryption method called Secure WPEG, or
shortly SECMPEG, designed for the MPEG-1 video standard. The SECMPEG I contains four
different levels of security. At the first level, SECMPEG encrypts the [headers from the sequence
layer to the slice layer, while the motion vectors and DCT [blocks are unencrypted. At the
second level, most relevant parts of the I-blocks are I additionally encrypted (upper left corner of
the block). At the third level, SECMPEG encrypts all I-frames and all I-blocks. Finally, at the
fourth level, SECMPEG encrypts the whole MPEG-1 sequence. The authors chose Data
Encryption Standard (DES) symmetric key cryptosystem, which was the natural choice, given
that this cryptosystem had been around since 1976 and was the official symmetric encryption
algorithm standardized by National Institute of Standard and Technology (NIST) and adopted by
the US Government. Since DES is a symmetric key cryptosystem, it could only be used to
achieve confidentiality. Meyer and Gadegast targeted solving the problem of data integrity as
well. For that reason, the Cyclic - Redundancy-Check (CRC) was incorporated as a low-level
solution to the integrity. The real data integrity mechanisms that included public key
cryptography and cryptographically good hash functions such as MD4, MD5, or SHA were left
for further research. [1]
The encryption in SECMPEG (levels 1, 2, and 3) has some weaknesses. It is own that
even though single P- or B-frame on its own carries almost no information tout the
corresponding I-frame, a series of P- or B-frames can tell a lot if their base I¬-frames are
correlated. Since SECMPEG introduces changes to the MPEG-1 format, a special encoder and
decoder is needed to handle SECMPEG streams. Nevertheless, the SECMPEG paper and
implementation my Meyer and Gadegast was one of the first important research initiatives for
selective encryption of multimedia streams.
1.1 BACKGROUND
The Video Encryption Algorithm (VEA) by Qiao and Nahrstedt is constructed with the
goal to exploit the statistical properties of the MPEG video standard. The algorithm consists of
the following four steps:
Step 1: Let the 2n byte sequence, denoted by ala2...a2n, represent the chunk of an I-frame
Step 2: Create two lists, one with odd indexed bytes ala3...a2n-l, and the other with even indexed
bytes a2a4...a2n.
Step 3: XOR the two lists into an n-byte sequence denoted with clc2...en
Step 4: Apply the chosen symmetric cryptosystem E (for example DBS or AES) with the secret
key KeyE on either odd list or even list, and thus create the cipher text sequence clc2...cn
EKeyE(ala3...a2n-l) or clc2...cnEKeyE(a2a4...a2ri) respectively.[1]
The partial encryption schemes for still images introduced by Cheng and Li are also
further extended to the videos. The approaches proposed by Cheng and Li are not suitable for
JPEG image compression, and thus naturally also not suitable for the MPEG video compression
standard. Instead, the partial encryption algorithms are designed for the video compression
methods, which use either quadtree compression or wavelet compression based on zero trees for
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the video sequence intraframes, motion compensation, and residual error coding. For example,
the partial encryption is applicable to the videos that are based on the Set Partitioning In
Hierarchical Trees (SPIHT) image compression algorithm, which is an application of zerotree
wavelet compression. Cheng and Li's partial encryption algorithms are designed to disguise the
intraframes (I-frames), the motion vectors, and the residual error code of the given video
sequences. In both quadtree compression and wavelet compression based videos, all I-frames are
encrypted using the previously discussed methods for partial encryption of still images by Cheng
and Li. In addition, it is also important to encrypt the motion vectors. [2].
2 PROPOSED PROJECT
This project will provide an encryption methodology with the bit-wise encryption. This
helps secure multimedia data files in such a manner that securing only information in the frame
data provides an effect of securing the file as a whole. The Matrix Encryption Algorithm consists
of a set of processing steps repeated for four rounds with 128 bit (16 bytes) of key. The
algorithm works on 16 bytes of data. We can divide the frame data in set of 16 bytes. Since, each
set is encrypted individually and independently. We can process each steps parallel, which will
increase the speed of encryption. Encrypting a bit stream, frame-wise at a fast rate is very
important aspect, when we consider the real time video streaming. We can achieve this faster and
stronger encryption can be achieved by parallel encryption of sets within the frame. This
securing process is to be carried out in a manner so as to reduce the amount of time used up in
securing the file.
2.1 FLEXIBILITY TO PERFORM SELECTIVE ENCRYPTION:
In the frequency domain, it is easier to identify what parts of the data are critical for
security purpose. This allows providing different levels of security and transparency.
Selective encryption is a technique aiming to save computational time or to enable new
system functionalities by only encrypting a portion of a compressed bit stream while still
achieving adequate security. Selective encryption as well as partial encryption, are applied only
on certain parts of the bit stream. In the decoding stage, both the encrypted and the nonencrypted information should be appropriately identified and displayed
Encryption can be performed on just audio/video frames, when performance of the takes
a major role. Thus selecting the part of the file, like just audio or just video, needs to be
encrypted only the frames respective to the selection, is encrypted. This improves the
performance of the encryption system, when we consider a large stream of video. Encryption can
be performed on complete video stream, which encrypts both audio and video frames.
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2.2 ALGORITHM
This project will encrypt only the selected frames in multimedia, render the file playable.
Each selected frames are encrypted separately.
Multimedia
Analyze to find out
frames to be encrypted
Selected
Encrypt frames
frames
Remaining frames
Encrypted
multimedia
Transmit
Network
Transmit
Multimedia
Unencrypted
Analyze as to which frames
to be decrypted
frames
Frames to be decrypted
Decrypt frame
Decrypted frames
Fig 1: Figure 1 illustrates a simplified implementation of the algorithm
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2.2.1
Matrix Encryption Algorithm
Figure 2 – Matrix Encryption Algorithm
1. Initial Round:
a. Divide the stream in frames to 16 bytes of sub-frames; consider it as a 4x4 matrix.
Each sub-frame is encrypted separately.
2. Rounds:
a. Operate on the part of matrix: Divide the matrix as 2x2 matrix (each cell will be
containing 2x2 matrix in it). Perform Xor operation on 1st part of the matrix with its
next one.
b. Operate with Key: Perform Xor operation on the 4x4 matrix with key of 16 bytes
(considering the key as 4x4 matrix for the operation)
c. Shift cells: shift the divided matrix cell values clockwise.
3. Final Round:
a. Append the encrypted sub-frames.
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The Algorithm is:
Step 1. Create matrix
Step 2. xor X00(00,01, 10, 11) with X01(02, 03, 12, 13) respectively which updates only 1/4th of
matrix.
Step 3. Rotate X00->X01->X11->X10->X01
Step 4. Add Key.
Step 5. Repeat step 2, 3, 4 for 3 more times. (Means all the 4 parts of matrix are updated).
Since the first step operates on itself (in all the 4 rounds, the same above operation
works), we need not to keep the s-Box like AES algorithm.
The second step is just like AES algorithm, it uses 16 bytes key, which will be XORed
with the resultant of the above step. (AES algorithm also uses 128 bit key, which mean 16 bytes).
The third step will actually shuffles the bytes in the matrix. Unlike AES, which will shifts
values within row. This algorithm will rotate the value position. The values changes row-wise as
well as column-wise.
2.3 SUMMARY OF MULTIMEDIA ENCRYPTION
Multimedia encryption involves changing the multimedia data stream itself to ensure
secure transmission of video data between client and server (or two nodes). It can be
accomplished by means of standard symmetric key cryptography where multimedia bit stream is
treated as a binary sequence and the whole data can be encrypted using conventional
cryptosystem such as AES or DES.
In general, when the application requirements are not dynamic (not a real-time streaming)
we can treat bit stream as a regular binary data stream and use the conventional encryption
techniques. Encrypting the entire multimedia stream using standard encryption methods is
referred to as the naive algorithm. There are many practical constraints in case of multimedia
which make such a scheme not practical in real-life scenario. Communication encryption of
multimedia content is a problem beyond the application of established encryption algorithms,
such as DES or AES, to its binary sequence. This is primarily due to the way multimedia is used
commercially. Unlike data encryption, where we want to encrypt a complete bit stream, mobile
multimedia encryption introduces several challenges. For example, the content providers want to
ensure real-time streaming of videos.
2.4 MP4
MP4 follows the ISO base format. The ISO Base Media File Format is designed to
contain timed media information for a presentation in a flexible, extensible format that facilitates
interchange, management, editing, and presentation of the media. This presentation may be
'local' to the system containing the presentation, or may be via a network or other stream delivery
mechanism. The file structure is object-oriented; a file can be decomposed into constituent
objects very simply, and the structure of the objects inferred directly from their type. The file
format is independent of any particular network protocol while enabling efficient support for
them in general. The ISO Base Media File Format is a base format for media file formats. One
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such being MPEG-4 is technically described by the ISO/IEC 14496-12, in accordance with its
compliance to the base format. [9]
Frames
Modern video file formats interleave audio and video to allow for playing even partially
loaded video stream on the network. And they also employ video compression methodologies to
conserve space. This compression is made possible by using relative references that is to say if
two consecutive frames have almost the same content except for partial changes, it is preferable
to record only the changes and use the reference frame to generate the current frame.
I-frame (intra-coded frame) is an infra-coded picture in effect a fully specified picture,
like a conventional static image file. I-frames are pictures coded without reference to any
pictures except themselves.
P-frame (Predicted frames) holds the changes in the image from the previous frame (Ex:
Moving a car across a stationary background, only car’s movement needs to be recorded).
B-frame (bi-directional predicted frame) helps specify the content by using differences
between the current and both preceding and following frames.
2.4.1
Fig: 3 Group of frames [11]
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3 PROJECT PLAN
The ultimate goal of this project is to provide an algorithm and methodology by which
the video and audio files are secured in time and space efficient manner.
3.1 SCHEDULE
This project is to be completed by the end of term, Spring 2014.
The following is a proposed schedule for the project:
January 27, 2014
Completed final project proposal
February 1, 2014
Begin project work
February 5, 2014
To start the coding in Vb
February 15, 2014
Discuss with advisor about the improvisations
March 1, 2014
To start draft of report and discussions with advisor
March 5, 2014
Final coding and UI
March 15, 2014
To finish final project report
April 10, 2014
To finish the project defense
May 20, 2014
End of spring 2014 term
4 DELIVERABLES
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The master project report satisfying the standards of the board
Working prototype of the algorithm.
Technical documentation and the resources to be used
A clean and user friendly user interface.
Complete implementation of the algorithm.
5 REFERENCES
[1]
Qiao, Lintian, and Klara Nahrstedt. "A new algorithm for MPEG video encryption." Proc. of First
International Conference on Imaging Science System and Technology. 1997.
[2]
Liu, Fuwen, and Hartmut Koenig. "A survey of video encryption algorithms."computers &
security 29.1 (2010): 3-15.
Lui, Oi-Yan, Ching-Hung Yuen, and Kwok-Wo Wong. "Chaos-Based selective encryption for AVS
video coding standard." Advances in Multimedia Information Processing–PCM 2012. Springer Berlin
Heidelberg, 2012. 501-512.
[4] Lim, Youngkwon, et al. "MMT: An Emerging MPEG Standard for Multimedia Delivery over the
Internet." MultiMedia, IEEE 20.1 (2013): 80-85.
[5] Ravishankar, K. C., and M. G. Venkateshmurthy. "Region based selective image
encryption." Computing & Informatics, 2006. ICOCI'06. International Conference on. IEEE, 2006.
[6] Multimedia Security Handbook by Borko Furht and Darko Kirovski, published by CRC Press LLC in
December 2004
[3]
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[7]
Forouzan, Behrouz A. 2008. Cryptography and Network Security. McGraw Hill higher Education.
ISBN 978-0-07-287022-0
[8]
QuickTime API Reference, 2005-08-11, Apple Computer, Inc. © 2005 Apple Computer, Inc.
[9]
http://en.wikipedia.org/wiki/Mp4
[10]
http://en.wikipedia.org/wiki/I-frame
[11]
http://cs.uccs.edu/~cs525/
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