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Encryption Algorithms and Data Types
              Taxonomy




           Selected Topics in Information Security – Bazara Barry
Introduction
Converged networks will be the common platform to carry
different types of data and traffic.

It is therefore important to classify different data types in
order to select the appropriate encryption algorithm(s) for
each data type.

The encryption algorithm should maintain the quality of
the specific data type after the decryption process,
reduce the mathematical computation, and keep balance
between performance and security




                    Selected Topics in Information Security – Bazara Barry
Data types Taxonomy
From network perspective and according to Khanvilkar et
al (2002) all the data types can be classified as either
Real-Time (RT) or Non Real-Time (NRT).

RT data types require strict delay constraints while NRT
data types do not, but they may have some constraints
on error.

Examples of NRT data types are text and images.




                  Selected Topics in Information Security – Bazara Barry
Data types Taxonomy
RT media can be classified into Discrete Media (DM) and
Continuous Media (CM).

This classification is based on whether the data is
transmitted into discrete quantum as a file or a message
or continuously as stream of messages with inter-
message dependency.

RT continuous media can further be classified as delay
tolerant (i.e. can tolerate high amount of delay without
significant performance degradation) or delay intolerant.




                  Selected Topics in Information Security – Bazara Barry
Data types Taxonomy
                                   Data types




           Non-Real Time                                                                    Real Time




   E.g. Text                   E.g. Images             Discrete                                 Continuous




                                                                  Delay tolerant            Delay intolerant



                                                                                            E.g. Streaming
                E.g. Instant                    E.g. Weather Updates                         Audio/Vedio
                Messaging




                                                  E.g. Remote Desk                     E.g. Interactive
                                                     Application                        Audio/Vedio




                                   Selected Topics in Information Security – Bazara Barry
Text Data
The most popular data types with many forms and
supporting protocols such as HTTP (i.e. used to transmit
HTML pages over the Internet), FTP (used to transfer
binary and ASCII files), SMTP (for exchanging
messages).

Bandwidth requirements of text mainly depend on its size,
which can be easily reduced using common compression
schemes such as LZW and Huffman coding.

Error characteristics of the text media are based on the
application under consideration (TCP, UDP).

Some text-based applications have real-time nature (IM),
whereas others do not (Web browsing).
                  Selected Topics in Information Security – Bazara Barry
Audio Data
Audio is a sound/speech converted into digital form using
sampling or quantization. It is transmitted over network as
discrete packets.

The required bandwidth for audio is based on its dynamic
range and/or spectrum. A number of compression
schemes are used for audio such as MPEG layer III,
GSM, Pulse Code Modulation.

Audio can tolerate up to 1 or 2% packet loss/error without
much degradation.

Real-time requirements of audio type depend on the
interactivity between the communication parties.

                   Selected Topics in Information Security – Bazara Barry
Graphics and Animation
Include static media like digital images and dynamic
media types like flash representations.

Bandwidth requirements can be reduced with
compression. Some popular compression schemes are
GIF, JPEG, and PNG.

They are error tolerant and can sustain packet loss.

Do not have any real-time constraints




                   Selected Topics in Information Security – Bazara Barry
Video
Video is a sequence of images/frames at a certain rate,
e.g. 24 or 30 frames/second.

Some compression schemes are MPEG-I, II, IV.

Real time requirements and error tolerance of video are
similar to audio.




                  Selected Topics in Information Security – Bazara Barry
Conclusion
Multimedia data have some characteristics that should be
taken into consideration when designing encryption
algorithms for them.

Some of these characteristics are: high data rate, high
quality, real time nature, continuity, loss-tolerance, error-
tolerance.




                    Selected Topics in Information Security – Bazara Barry
Encryption Algorithms
Can be classified into shared (secret) key algorithms,
public key algorithms, and hash functions.

Classical and modern ciphers have all been developed
for the simplest form of multimedia data, i.e., text, and are
not appropriate for higher forms such as images and
video with very large file sizes.

A major recent trend is to minimize the computational
requirements for secure multimedia distribution by
―selective encryption‖ where only parts of the data are
encrypted.



                    Selected Topics in Information Security – Bazara Barry
Video Encryption Algorithms
1.    SECMPEG by Meyer and Gadegast, 1995
2.    Aegis by Maples and Spanos, 1995
3.    Zigzag Permutation Algorithm by Tang, 1996
4.    Video Encryption Algorithm by Qiao and Nahrstedt, 1997
5.    Video Encryption Algorithms by Shi, Wang and Bhargava I, II
      (VEA), III (MVEA), and IV (RVEA) 1998 and 1999
6.    Video Encryption Methods by Alattar, Al-Regib and Al-
      Semari, 1999
7.    Partial Encryption Algorithms for Videos by Cheng and Li,
      2000
8.    MHT-Encryption Scheme and MSI-Coder by Wu and Kuo,
      2000 and 2001
9.    Format-Compliant Configurable Encryption by Wen et al.,
      2002
10.   Selective Scrambling Algorithm by Zeng and Lei, 2002



                    Selected Topics in Information Security – Bazara Barry
Image Encryption Algorithms
1. Selective Encryption Methods for Raster and JPEG Images by
   Droogenbroeck and Benedett, , I and II, 2002
2. Selective Bitplane Encryption Algorithm by Podesser, Schmidt and
   Uhl, 2002




                      Selected Topics in Information Security – Bazara Barry
Audio Encryption Algorithms
1.   ENCRYPTION OF COMPRESSED SPEECH
     a.   Selective Encryption Algorithm for G.723.1 Speech
          Codec by Wu and Kuo, 2000
     b.   Perception-Based Partial Encryption Algorithm by
          Servetti and De Martin, 2002
2.   ENCRYPTION OF COMPRESSED AUDIO
     a.   MP3 Security Methods by Thorwirth, Horvatic, Weis
          and Zhao, 2000




                  Selected Topics in Information Security – Bazara Barry
Performance Metrics to be Considered
1. Latency (the time it takes for a multimedia transmission
   to go from its source to its destination
2. Jitter (Non-uniform delays)
3. Packet Loss
4. Bandwidth and Effective Bandwidth




                   Selected Topics in Information Security – Bazara Barry
Encryption Solutions for VoIP
The IETF has chosen three security protocols in the SIP
standard, namely, Transport Layer Security (TLS),
Secure/Multipurpose Internet Mail Extensions (S/MIME),
and Secure Real-Time Transfer Protocol (SRTP)—to be
used for securing SIP service.

The basic approach consisted of adding a security layer
below the existing VoIP protocol rather than crafting a
new security protocol, which helps in terms of existing
protocol implementation reuse.




                  Selected Topics in Information Security – Bazara Barry
Encryption Solutions for VoIP




              Selected Topics in Information Security – Bazara Barry
SRTP: Voice/Video Packet Security
SRTP, specified in RFC 3711, describes how to protect
telephony media by encryption of the RTP packet
payload, authentication of the entire RTP packet, and
packet replay protection

The protocol is located between the RTP application and
RTP transport layers. It secures the confidentiality of RTP
payloads and the integrity of all RTP packets by adopting
the AES using a symmetric cryptographic key. The
payloads from the RTP application are encrypted and
encapsulated into an SRTP packet.




                   Selected Topics in Information Security – Bazara Barry
Confidentiality




                  Selected Topics in Information Security – Bazara Barry
Message Authentication




              Selected Topics in Information Security – Bazara Barry
Replay Protection




              Selected Topics in Information Security – Bazara Barry
References
1. X. Liu, and A. M. Eskicioglu, ―Selective Encryption of Multimedia Content in
   Distribution Networks: Challenges and New Directions,‖ In Proceedings of
   IASTED International Conference on Communications, Internet and
   Information Technology (CIIT 2003), Scottsdale, AZ, USA, Nov 2003.
2. T. Porter, Practical VoIP Security. Rockland, MA: Syngress, 2006, Ch 14.




                        Selected Topics in Information Security – Bazara Barry

								
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