MEDICAL VERIFICATION WATERMARKING FOR

HEALTHCARE INFORMATION MANAGEMENT

Ki-Ryong Kwon, Seung-Seob Park

Division of Electronics, Computer & Telecommunication Engineering, Pukyong National University, South Korea

Suk-Hwan Lee

Department of Information Security, Tongmyong University, South Korea

Keywords: Medical image, Watermarking, Integrity verification, Healthcare information management.

Abstract: This paper presents a verification watermarking applied to healthcare information management. The

proposed method uses the whole region based on the public-key cryptograph, which is transformed by the

DWT transform to integrity verification. Furthermore, the public-key cryptograph algorithm is used for the

embedded watermark image. We adaptively select the upper bit-plane including the LSB parts of each block

when the watermark is inserted.

1 INTRODUCTION

With the development of information

communication and computer technology, there has

been come to digital hospital age that can be

received remote medical treatment in network by

database of digital medical image.

Images that were taken by various image

modalities are digitalized through CR (computed

radiography). PACS (picture archiving and

communication system) is a system that stores these

images on storage media such as a hard disk and

transmits them to each terminal via network. With

this system, doctors can monitor the images of the

patients in real time wherever they have a

workstation like a hospital or a consulting room. As

a result, we can computerize and manage the

medical images, related clinical information, and

ADT effectively through the nexus between PACS

and HIS (hospital information system)

(http://www.pccgroup.com), http://www.dicomana-

lyser.co.uk). In addition, with the development of

superhighway, it is possible to provide remote

diagnosis and consultation and to pay for insurance,

and to use as data to go on in the Military Manpower

Administration by transmit this medical information

via open-end network such as internet. However,

there are some issues raised by the system, i.e.

security problems of medical information, such as

illegal reproduction of medical images and

proprietary rights, and data authentication. Providing

a duplicated CD is weak in reissuance of medical

certificates by illegal forgery, or misapplication for

draft evasion.

Anand et al. (Anand and Niranjan, 1998)

proposed a watermarking method that puts data

between medical images for watermarking of

medical images. That is, a text document and data

such as E.C.G is encoded together into the LSB,

which is less important bit in the gray level pixel,

and inserted between the medical images such as CT

images. Wakatani et al. (Wakatani, 2002) proposed a

method that inserts a watermark into the surrounding

regions of ROI (region of interest) of a medical

image by using encoded signature image. This

method generates a bit stream by its importance,

after subdividing the original image into ROI region

and encoding the signature by gradual code. Then,

this method inserts the bit stream into the area pixels

around ROI with spiral and encodes it by HS

(hierarchical segmentation) algorithm.

Thus, in this paper, as a counterproposal for the

integrity and copyright protection of the medical

images, we propose a medical image protection

system that applied digital watermarking technology,

which provides proprietary and data authentication

of the multimedia contents. Proposed method used

DWT transformation method based on open key

523

Kwon K., Park S. and Lee S. (2010).

MEDICAL VERIFICATION WATERMARKING FOR HEALTHCARE INFORMATION MANAGEMENT.

In Proceedings of the Third International Conference on Bio-inspired Systems and Signal Processing, pages 523-527

DOI: 10.5220/0002742005230527

 SciTePress

coding to verify integrity. That is, to generate a

watermark, this method transforms an original image

onto wavelet domain and resolves the most low

frequency image into bit plane. Then, to authenticate

its proprietary, it maps the image with the logo

image of LSB and displaces randomly. In addition, it

divides the original image into blocks to embed a

watermark and assigns the insertion position of the

watermark randomly. In a selected block, a bit plane

in the embedding position of the watermark is

initialized to zero and execute the XOR operation

with the watermark information using hash function.

Inserted watermark image uses an open key security

algorithm for more robust integrity verification.

With embedding a watermark, we select the upper

bit-plane adaptively that includes the LSB parts of

each block, so the position the watermark inserted

does not appear. This proposed algorithm is robust

that attackers cannot modify or remove the original

watermark. Experimental results show that integrity

verification is more robust and invisibility is

superior to the previous algorithms.

2 PROPOSED INTEGRITY

WATERMARKING SCHEME

2.1 Embedding Process

The overall diagram of proposed watermarking

embed is shown in Figure 1. First, to create

information of a watermark, original images is

transformed as two levels by DWT. To make the

LL2, which is a basis region found, as binary bit, we

organize the eight bit-planes. For the reorganization

of the bit-plane, m bits contrast is expressed as Eq.

(1), which is a polynomial with two bases.

2222 aaaa

++++

−

(1)

The obtained bit-plane information is mapped

within the same size of the original image. At this

time, we used a school logo rather than a bit-plane

value in the LSB, so it means the copyrighter’s

position when the watermark is extracted. Each bit-

plane information for the rest upper seven bits,

which is inserted twice, expands the number of

possible comparison for estimating integrity of the

watermark. Then, for the security of the bit-plane

information according to each bit, random

transposition is executed. M and M/2 are 512 and

256. We used a random noise form from the

separately performed random displacement of the

two regions as watermark information.

Figure 1: A block diagram of the proposed watermarking

algorithm to embed a watermark.

}

',0,',0|)','(),({

)(

jjMiijiwjiw

WnpermutatioW

≤≤≤≤==

(2)

The embedding position of the watermark is the

image block, which is randomly selected within the

lower three bits of the original image, and the ROI

region becomes the LSB. These requirements

prevent a wrong diagnosis by the watermark

information in the property of medical images. In

common cases, the central region in the image is the

object for the ROI region, and in a particular case,

the object may be assigned.

In the Eq. (3),

X means the zero-initialized

relevant region

X in the block, which is randomly

selected and includes a watermark. M and N mean

the horizontal and vertical size of the image.

P is a

bit stream that passed the MD5 cryptograph hash

function H(.) with

X and M, and N. The Eq. (4) is

a result of the XOR operation between the bit stream

and the watermark information

B . The public-key

cryptograph system cryptographers

W as shown in

Eq. (5).

E (.) is a public-key cryptograph system

and K’ is a personal-key. The watermarked image is

generates by inserting the data

C into '

X .

128),,,,()',,(

== spppXNMH

(3)

RRR

BPW ⊕=

(4)

)(

' RKR

WEC

(5)

The procedure to embed a watermark is as follows.

[The embedding procedure]

BIOSIGNALS 2010 - International Conference on Bio-inspired Systems and Signal Processing

524

(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

' are used for the inputs of

the MD5 cryptograph hash function.

(8) The XOR operation is performed between

the watermark information and P

generated by ⑦.

(9) A public-key cryptograph system

cryptographers W

, which is a result from (8).

(10) W

is putted into X

' 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

', which is a result of initializing a

block Z

that has a watermark as 0, and a block that

includes a watermark value. A hash value from Z

and the image size M and N creates Q

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

as 0.

(2) Through a hash value from Z

‘ and M and

N, Z

, the size of 64 bits, is created

(3) A watermark-embedded block G

decoded as a public-key.

(4) The XOR operation is performed between

and U

(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

525

to estimate robustness of the image. When the

correlation is not about 1, then the algorithm regards

the transmitted medical image as a modified one and

requires retransmission. Otherwise, it extracts the

watermark and determine the image was forged or

not by verification through the watermark.

∑∑

−

12/

)],([

),(

jiW

jiWjiW

(8)

),( jiW means the embedded watermark, and

),(

jiW means the extracted watermark.

(a) (b)

Figure 3: (a) Brain Image, (b) Watermarked Brain Image,

(c)) Spine Image, and (d) Watermarked Spine Image.

On the simulation of the DWT generation

algorithm based on the public-key cryptograph

algorithm, Brain and Spine, and Chest images was

used with 512x512 sized. The coefficient of the

wavelet filter bank uses Daubechies D4 and the

original image was wavelet-transformed by binary

level.

Invisibility of the watermark for Brain and Spine

images are shown in Fig. 3. The original Brain

image is shown in (a). The PSNR of the watermark-

embbeded image, shown in (b), is 43.49[dB]. The

original Spine image is shown in (c). The PSNR of

the watermark-embbeded image, shown in (d), is

43.68 [dB].

On the simulation of Brain image using the DWT

generation method based on the public-key

cryptograph algorithm, we transformed the images

512x512 sized to binary level by the wavelet

transform. The basis region image of the LL2, which

was transformed by the binary level DWT, is shown

in Fig. 4 (a). Its size is 128x128. The logo image

will be embedded into the LSB of the bit-plane band

for copyright verification. The mapped image about

bit-plane of the LL2 basis region image is shown in

Fig. 4 (b). The LSB bit-plane image replaces the

logo image for copyright verification. The divided

image, shown in (b), will include the mapped bit-

plane image. A medical image, whose ROI region

was severely forged, is shown in Fig. 5 (a). A

watermark-extracted image is shown in Fig. 5 (b)

and its NC value is 0.88. It means the medical image

was forged. We transposed the watermark of the two

layers randomly for integrity of the forged medical

image. With looking at them, we can notice they

were forged.

(a) (b)

Figure 4: (a) Watermark information for Brain Image and

(b) bit-plane mapped images and divided images.

(a) (b)

Figure 5: (a) Illegally manipulated image and (b)

Watermark-extracted image (NC=0.88).

With the results of simulation, invisibility is

excellent even though the position of the watermark

is expanded from the LSBs to MSBs. In addition, it

is possible to verify integrity by extracting the

embedded watermark from a forged image. Thus,

the proposed method helps to prevent problems with

illegal manipulation of medical images, such as

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526

military service absurdity or medical insurance

fraud.

Figure 6: Extracting the watermark and verifying integrity.

4 CONCLUSIONS

To protect integrity and copyright protection of

medical images, we proposed a medical image

protection system by applying the digital

watermarking algorithm that provides copyright and

authentication of the multimedia contents. For

integrity verification, the proposed method uses the

whole region based on the public-key cryptograph,

which is transformed by the DWT transform. To

create a watermark, the wavelet-transformed

watermarking method based on the public-key

cryptograph divides the lowest frequency image into

bit-planes. They are transposed randomly by

mapping with the logo image of the lowest bit to

verify its copyright. This proposed algorithm is

robust that attackers cannot modify or remove the

original watermark. Experimental results show that

integrity verification is more robust and invisibility.

ACKNOWLEDGEMENTS

This work was supported by the Korea Research

Foundation Grant funded by the Korean

Government (MEST)"(KRF-2009-0071269)

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