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(1) To generate watermark information, the
DWT is executed for the original image by two
levels.
(2) The composed 8-bit bit-planes make the
LL2 as binary.
(3) Bit-plane information is mapped as the same
size of the original image.
(A school logo was inserted rather than the bit-
plane value of the LSB to express the copyrighter’s
position.)
(4) For protecting the bit-plane information for
each bit, M and N is randomly displaced as two
regions, 512 and 256, separately.
(5) The watermark embedding position is the
image block, which is randomly selected and is
within the lower 3 bit of the original image, and the
ROI region becomes the LSB.
(6) The selected image block is initialized.
(7) M and N, and X
R
' are used for the inputs of
the MD5 cryptograph hash function.
(8) The XOR operation is performed between
the watermark information and P
R
generated by ⑦.
(9) A public-key cryptograph system
cryptographers W
R
, which is a result from (8).
(10) W
R
is putted into X
R
' and a watermarked
image is obtained.
Figure 2: A block diagram of the proposed watermarking
algorithm to extract a watermark.
2.2 Extracting Process
The procedure extracting a watermark in the
watermark-embedded image is shown in Fig. 22.
First, the watermarked image is divided into two
regions, a block Z
R
', which is a result of initializing a
block Z
R
that has a watermark as 0, and a block that
includes a watermark value. A hash value from Z
R
'
and the image size M and N creates Q
R
of 64 bits.
The block that has watermark information is
decoded as a public-key as shown in Eq. (6). Then,
the XOR operation shown in Eq. (7) extracts the
embedded watermark information, which is a form
of random noise.
)(
RKR
ZDU =
(6)
RRR
UQO ⊕=
(7)
At this step, deteriorated part comes out if the
watermarked image was manipulated. Unless the
attack was severe, however, the part does not appear
sufficiently since it is a form of random noise. For
perfect integrity verification, we perform random
inverse transposition to make it as 7-bit bit-plane,
and combine them to organize an image. The
position information of the LSB corresponds to the
lowest bit finds the copyrighter’s position by a
school logo. Verifying the obtained two images and
the watermarked image helps to estimate integrity.
We can find the part that has a problem through the
combined two images if a certain part of the
watermarked image was manipulated, so it is
possible to estimate integrity by compare it with the
distorted image.
The procedure for extracting a watermark is as
follows.
[The extracting procedure]
(1) A watermarked image is divided into a
watermark-inserted block and a block that is a result
of initializing Z
R
as 0.
(2) Through a hash value from Z
R
‘ and M and
N, Z
R
, the size of 64 bits, is created
(3) A watermark-embedded block G
R
is
decoded as a public-key.
(4) The XOR operation is performed between
Q
R
and U
R
.
(5) Inverse random transposition produces 7-bit
bit-planes of the original image. Then the algorithm
makes the combined two image with a school logo
pattern, and compare it with the watermarked image.
3 EXPERIMENTAL RESULTS
Computer simulations were carried out to
demonstrate the performance of the proposed
watermarking method. Performance of the PC is
Pentium4 CPU 3GHz, 512MBRAM. We changed
the stored files to common image data through the
program VisualGate, which is offered on
http://www.infinitt.com/ and stores image files with
the form of DICOM. To estimate subject
performance of invisibility, we generated many
watermark-embedded images through various
algorithms. The PSNR (peak signal-to-noise ratio)
was used as an objective measure. The NC
(normalized correlation), shown in Eq. (8), was used
MEDICAL VERIFICATION WATERMARKING FOR HEALTHCARE INFORMATION MANAGEMENT
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