CS631 Paper Response Form
Paper Title: Methods for Encrypting and Decrypting MPEG Video Data Efficiently
Author(s): Lei Tang
Main Point(s):
Common enryption techniques like DES are simply too slow for the vast amount of data in
multimedia applications. Tang therefore proposes a light-weight encryption method that
does not encrypt the data itself but instead modifies a parameter of the compression
algorithm. The basic idea for encrypting MPEG data is to use a (secret) random order
for reading an 8x8 block into a 64-valued vector. The problem with this is that the
DC value that carries most of the information would be easily detectable since it is
the biggest value. Tang solves this by dropping the 64th coefficient altogether, splitting
the DC value into two 8 bit halves which he puts into the 0th and the 64th coefficient
before permuting them. Two proposed extension are to encrypt 8 DC coefficients at a time
using DES or to use two different, randomly applied permutation vectors.
Possible Use(s):
Multimedia Security is important for trading multimedia data (e.g. VOD) and to ensure
privacy for web users.
Extensions:
I really don't understand enough of encryption to know what kind of techniques can
be broken if plaintext is available or where the weaknesses of his two extensions
are. The only obvious thing I could think of is to apply the basic idea of encrypting
a parameter of the compression algorithm to the other compression algorithms that
exist for video. I don't know how audio is encrypted, maybe there are similar compression
algorithms where this method could be applied.
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