A Secret Information Hiding Scheme Based on Switching Tree Coding Speaker: Chin-Chen Chang.

A Secret Information Hiding Scheme Based on

Switching Tree Coding

Speaker: Chin-Chen Chang

Outline

VQ image compression

Watermarking

Search order coding (SOC)

Switching tree coding (STC)

VQ Image Compression

ImageIndex table

Vector Quantization Encoder

VQ Compression

ImageIndex table

Vector Quantization Decoder

VQ Compression

PSNR = 29.62 dB Accuracy rate 99.95%

Watermarking

CODEBOOK

Finds the nearest pairs

Find d(CW0, CW8) > TH

d(CW13, CW14) > TH

Unused

CW0, CW8, CW1

3, CW1

hide 1

hide 0

CW4, CW5

CW6, CW7

CW15, CW10

CW12, CW9

Original Image Index Table

Index TableUnused

CW0, CW8,

CW13, CW14

Encode

Water mark: 1 0 1 0 1 0 0 1 0 1 1 1 1 0 0

Index Table

00 0 1

0 11 1

CW1, CW2,

CW4, CW5

CW6, CW7

CW11, CW3

CW15, CW10

CW12, CW9

hide 1 hide 0

Water mark

Water mark: 1 0 1 0 1 0 0 1 0 1 1 1 1 0 0

Index Table

00 0 1

0 11 1

CW1, CW2,

CW4, CW5

CW6, CW7

CW11, CW3

CW15, CW10

CW12, CW9

hide 1 hide 0

Water mark

Water mark: 1 0 1 0 1 0 0 1 0 1 1 1 1 0 0

Index Table

00 0 1

0 11 1

Water mark

Search-Order Coding (SOC)

An example for indices of VQ

6 7 8 9 10

Searched point Non-searched point

31 207 207

31 207 8 20731 211 8 735 31 8 7

The compressing steps

P1 = 1 00011111

Indicator

P2 = 1 11001111

P3 = 0 00

P6 = 0 10

Compression codes = 100011111 111001111 000 …

Information hiding on the SOC codes

The proposed scheme: - Information hiding: to embed secret data into host image - Steganography :

to embed secret data into host image and the interceptors will not notice the existence of secret data

- Based on SOC

Main idea:Ex. receiver receives the compression codes : 010101101110110110011000011

SOC SOC SOCOIVOIV(original index value)

It means that the embedded secret data is “01100” if SOC is represented to hide “0” and OIV is represented to hide “1”.

Method:ex. A 3*3 index table:

1 18 21 31

2 30 30 31

3 29 30 32

If the secret data is “111110100”, then the hiding position of each bit will be in the raster scan order.

Embedding phase:

Defined: “0” embedded into SOC and

“1” embedded into OIV.

SOC ====> there is nothing that needs to change for its

compression codes

hide “0”

SOC ====> translate SOC into OIV

(give up SOC coding and keep the OIV)

hide “1”

OIV ====> there is nothing that needs to change hide “1”

OIV ====> translate OIV into SOC

hide “0”

+ OIV11(SOC)

compression codes are still OIV: 100010010

translate SOC into OIV : 000 => 100011110

translate OIV into SOC : 100100000 => 01100100000

Cost table (bits):

Security: For enhancing the security of our

method, the position in the index table for hiding each bit of secret data can be determined by using pseudo random number generator, and the secret data can be encrypted by using traditional cryptography system such as DES or RSA in advance.

Experimental results

Switching tree coding (STC)

Switching-tree coding (STC)

Sheu proposed the STC algorithm in 1999

Re-encode the index table

the current index

Switching-tree coding (STC)

If P = 7, then P = U P’ = ‘11’

If P = 10, then P = L P’ = ‘10’

If P = 14, then P = A in index (3) P’ = ‘01’ || index (3) = ‘0100011’

If P = 17, then P’ = ‘01’ || (17) = ‘0010001’

Information Hiding on the STC codes (IHSTC)