Secure Multicast of Anti-Collusion
Hong Zhao and K. J. Ray Liu
Fingerprinted Video
Communication and Signal Processing Lab
1. Motivation
3. A Joint Fingerprint Design and
Distribution Scheme
• Multimedia Fingerprinting:
™
™
™
™
™
A huge volume of data and a large number of users
Unicasting each fingerprinted copy is inefficient
Traditional multicast cannot be directly applied
™
Robust against collusion attacks and other attacks
Preserve the secrecy of the embedded fingerprint
Achieves bandwidth efficiency
(1)
™
Robust against many attacks and widely used in
multimedia fingerprinting
Not all coefficients are embeddable due to perceptual
constraints, and a non-embeddable coefficients has
the same value in all copies
• A general fingerprint multicast scheme:
™
™
Non-embeddable coefficients Æ multicast to all users
Uniquely fingerprinted coefficients Æ unicast
• Can be used with most spread spectrum
embedding based fingerprint design:
(2)
u u u
U 1,1
(3)
u
(4)
(5)
u u
U1,2
(6)
u
(7)
(8)
N
VLC-1
Positions of embeddable coeff.
Encrypt
VLC
Y
Embeddable?
Q-1
Q
VLC
User u(i)’s fingerprint
Multicast
to all users
Encrypt
™
VLC-1
Q-1
Multicasted
coded DCT
coeff.
Positions of
embeddable
coeff.
Reconstruct
the 8*8
DCT block
Motion vector
u
(10)
Improve the perceptual quality (1~1.5dB) without
extra communication overhead
™
2,2,3
(11) (12)
u u
U 2,2
Motion vectors,
Positions of embeddable coeff.
quantization factors
and side info
VLC
N
VLC-1
™
If TDMA based fingerprint modulation is used, then
some fingerprinted coefficients are also shared by the
users in the same subgroup.
™
Achieve both the robustness and bandwidth efficiency
Explore the special structure of the fingerprint design
to further improve the bandwidth efficiency
¾
™
Shared fingerprinted coefficients Æ multicast to the
users in the subgroup
Increase the complexity of the underlying network and
that of the sender and the receivers
VLC-1
Embeddable?
Y
Q-1
W1(i1 )
∈ S1? Y
Unicast
to user i
for user u(i)
Q
VLC
N
Encrypt
#
#
WL(i1 ,",iL )
Q
K (i )
VLC
Encrypt
0
Motion
compensation
(b) Decoding at the receiver’s side
A MPEG-2 based general fingerprint multicast scheme for
video-on-demand applications
Coded DCT coeff.
unicasted to user u(i)
#
Coded DCT coeff.
multicasted to
subgroup U(i1)
VLC-1
Decrypt
VLC-1
Q-1
Decrypt
Coded DCT coeff.
multicasted to all users K m
VLC-1
Q-1
Drift compensation signal
-
DCT motion
Motion vectors
compensation
+
-
5. Bandwidth Efficiency
M=1000, L=3
D=[2, 5, 100]
ρ=[1/4,1/4,1/2]
M=5000, L=4
D=[2, 5, 5, 100]
ρ=[1/6,1/6, 1/6,1/2]
M=10000, L=4
D=[4, 5, 5, 100]
ρ=[1/6,1/6, 1/6,1/2]
™
Unicast to user
u(i)
™
™
Positions of embeddable coeff.
Unicast
to user i
FP drift compensation in general fingerprint multicast scheme
for user u(i)
Reconstruct
the 8*8
DCT block
K (i )
L’
MG(L’)
RB(L’)
Miss am
Carphone
Flower
0
1
2
0
1
2
3
0
1
2
3
1
3
13
1
3
13
65
1
5
25
125
2
3
4
2
3
4
5
2
3
4
5
0.23
0.22
0.20
0.18
0.16
0.15
0.14
0.16
0.14
0.13
0.13
0.41
0.34
0.31
0.35
0.30
0.27
0.25
0.34
0.28
0.26
0.23
0.52
0.43
0.39
0.46
0.39
0.35
0.32
0.43
0.37
0.33
0.30
• Bandwidth efficiency of the two schemes:
Q-1
#
K (i1 )
Encrypt
for embeddable
coeff. ?
6. Conclusions
for subgroup U(i1)
Multicast to
subgroup U(i1)
K (i)
Decrypt
Reconstruct
the 8*8
DCT block
VLC
+ Y
User u(i)’s
fingerprint
(a) Fingerprint embedding and distribution at the server’s side
IDCT
Q-1
Q
Q-1
Km
K ( i1 )
Y
Q-1
Multicast to
all users
Encrypt
VLC
N
K
Multicast
to all users
m
for user u(i)
Q-1
• Joint fingerprint design and distribution scheme:
™
Encrypt
Embeddable?
Coded DCT
coeff.
• In the tree based fingerprint design, some
fingerprints are shared by a subgroup of users
∈ SL? Y
Q-1
a2,2,1a2,2,2a
Some users are more likely to collude with each other
than others due to geographical or social reasons
Group users who are more likely to collude with other
together to be more robust against collusion attacks
(a) Fingerprint embedding and distribution at the server’s side
Unicasted coded
DCT coeff.
VLC-1
(9)
• Tree based fingerprint design:
Km
K (i )
• Fingerprint drift compensation:
a2,2
u u
U 2,1
Motion vectors,
Positions of embeddable coeff.
quantization factors, etc.
Motion vectors,
quantization factors
and side info
™
a2,1
a1,1,1 a1,1,2a1,1,3 a1,2,1 a1,2,2 a1,2,3 a2,1,1a2,1,2a2,1,3
™
™
a1,2
a1,1
2. General Fingerprint Multicast
• Spread Spectrum Fingerprint Embedding:
a2
a1
• Desired distribution schemes:
™
The encoder and decoder use reconstructed
unfingerprinted and fingerprinted copies for motion
compensation. Æ The difference: the embedded FP.
FP from different frames may accumulate
™
Protect multimedia content after decryption
Embed identification info. in each distributed copy
• Distribution of Fingerprinted Copies:
™
4. Fingerprint Drift Compensation
• Fingerprint drift:
IDCT
0
Motion
compensation
(b) Decoding at the receiver’s side
A MPEG-2 based joint fingerprint design and distribution
scheme for video-on-demand applications
General fingerprint multicast: reduces the
communication cost by 48% ~ 84%.
Joint fingerprint design and distribution: reduces the
communication cost by 57% ~ 87%.
Depend on: the number of users, the characteristics
of sequences & network and computation constraints
• Comparison of the two schemes:
™
™
General fingerprint multicast: recommended for
sequences with fewer embeddable coefficients.
Joint fingerprint design and distribution: preferred on
sequences with much more embeddable coefficients.