SECRET DATA HIDING IN ENCRYPTED

COMPRESSED VIDEO BITSTREAMS FOR PRIVACY

INFO PROTECTION

presented by,

Pradeep Rajagopalan

Easwari Engineering College, Anna University

Chennai

Introduction

Need For Video Encryption or steganography: The primary need for this type of encryption is to send a secret

message from one place to another without getting hacked.

Video encryption is more secured than image encryption

because its difficult to find on which frame the secret data is

hidden

Applications: Copyright Protection

Medical and Surveillance systems

Multimedia Security

Proposed Model

In this paper, A novel scheme of data hiding in the compressed

version of H.264/AVC videos is presented, which includes

three parts:

• H.264/AVC video encoding and secret message encryption.

• Data embedding

• Data extraction

The content owner encrypts the original H.264/AVC video

stream using standard stream ciphers with encryption keys to

produce an encrypted video stream

After the compression process the encoded bit streams are

going to encrypted using chaos encryption method.

Proposed Model

Then, the data-hider (e.g., a cloud server) can embed the additional

data into the encrypted video stream by using bit wrapping method,

without knowing the original video content.

At the receiver end, the hidden data extraction can be accomplished

either in encrypted or in decrypted version.

Secret Message Encryption

In this section, We will see how a Secret Message is

encrypted.

Symmetric-key algorithms are a class

of algorithms for cryptography that use the

same cryptographic keys for both encryption

of plaintext and decryption of ciphertext.

In this paper I have used Chaotic Encryption technique

which is an example of Symmetric Keying .

Secret Message Encryption

Chaos Encryption:

This method is one of the advanced encryption standard to

encrypt the message for secure transmission.

It encrypts the original secret message’s ASCII values with

encryption key value generated from chaotic sequence with

threshold function by bitxor operation

Here logistic map is used for generation of chaotic map sequence.

It is very useful to transmit the secret message through insecure

channel securely which prevents data hacking.

Secret Message Encryption Flow

Secret message

Initiate Constant factors (u,x)

Chaotic Sequence Generation

Threshold function

Bit XOR

Encrypted Secret

message

Xn+1 = u*x(1-x)

(I/255)< Xn+1 < (I+1)/255

Eij = Pij (bitxor) I

H.264 Coding

H.264 coder is based on multiscale 2D DWT and exploits the

self-similarity across scales by using set partitioning.

After transformation, the coefficients are ordered into a tree

structure, called spatial orientation tree (SOT).

The SOT is defined by each wavelet coefficient (parent) in a

certain decomposition scale has either no child (i.e., tree

leave) or four children in the next finer scale and the

coefficients in the low-frequency subband are the tree roots.

The coefficients are quantized by partitioning them into

different set likes significant information and insignificant

informations and performs the priority based transmission.

Continues…

• The algorithm is based on 3 concepts

Ordered bit plane progressive transmission.

Set sorting algorithm.

Spatial orientation trees

In a practical implementation the significance

information is stored in three ordered lists

LIS-list of insignificant sets

LIP-list of insignificant pixels

LSP-list of significant pixels

Set Partitioning Sorting Algorithm

The sorting algorithm divides the set of pixels

into partitioning subsets Tm and performs the

significance test by using the function

Sn(T) =

1, max{ (i, j) € T | |Ci, j| > 2n }

0, otherwise

• n is the # of pass

Examples

Encoder---First Pass

6

4 -3

-2 0

26

7-7

13 10

6 4

4 -4

2 -2

InitializationChose T0 = 2└log226┘= 16; (n = 4)LIP = { } LSP = { }LIS = { }

1. Process LSPSn(0,0) 26 ≥ T0, we transmit 1; 26 > 0, we transmit 0;Then move (0,0) to LSP and magnitude will be checked (+ve=0;-ve=1),therefore Sn(0,0)=1 0.Sn(0,1), Sn(1,0), Sn(1,1) are insignificant, transmit three 0;

2. Process LISSn( D(0,1) ) 13, 10, 6, 4 < T0, we transmit 0;Sn( D(1,1) ), Sn( D(1,0) ) are insignificant, transmit two 0;

3. Needn’t to process LSP (because LSP = NULL)4. Update:

The transmitted bit stream 10000000 (8 bits)LIP = { (0,1), (1,0), (1,1) }LIS = { D(0,1), D(1,0), D(1,1) }LSP = { (0,0) }

Data Embedding

Adaptive LSB Embedding:

A 8-bit gray scale image matrix consisting m × n pixels and a

secret message consisting of k bits.

The first bit of message is embedded into the LSB of the first

pixel and the second bit of message is embedded into the second

pixel and so on.

The resultant Stego-frame which holds the secret message is also

a 8-bit gray scale image and difference between the cover frame

and the Stego-frame is not visually perceptible.

The quality of the frame, however degrades with the increase in

number of LSBs.

This hiding process will introduce the error between input and

output frame and it is determined by mean square error and Peak

signal to noise ratio determines the image quality.

Algorithm Flow

Decomposed Frame

Select reserved Coefficient from High freq bands

Message bits – 00110110

Coefficient- 00011010

Pay load-3 bits per pixel

Coefficient before embedding

– 00011000

After LSB Replacement,

The coefficient will be

00011001Inverse TransformStego Frame

Secret Data

Data Extraction

At this stage, frame and secret hidden text messages are

extracted from stego encrypted image. The secret data can be

extracted from the embedded image with help of key matrix.

This extraction process is opposite to data embedding, pixel

coefficient and embedding rate are used here to extraction of

data.

Finally, Extracted secret text data is in the form of cipher

text and then convert into plain text using chaos decryption

process.

Adaptive LSBs Extraction

A 8-bit gray scale image matrix consisting m × n pixels and a

secret message consisting of k bits.

The first bit of message is extracted from the LSB of the first

high frequency coefficients and the second some bits of

message is extracted from the second reserves coefficients and

so on.

This process is repeated upto all secret message bits are

retrieved and these bits are grouped into 8bits to form a

character values.

The extraction of desired payload number of bits will be

performed by using logical bitwise operators called ‘bitand’

and ‘bitor’.

Finally all extracted message characters are applied to Chaos

decryption module to decrypt the data.

Secret Message Decryption

Chaos Decryption

This method is one of the advanced encryption standard to

encrypt/decrypt the image for secure transmission.

It decrypts the encrypted secret message ASCII values with

decryption key value generated from chaotic sequence with

threshold function by bitxor operation

Here logistic map is used for generation of chaotic map

sequence.

Secret message Decryption Flow

Encrypted secret message

Initiate Constant factors

Chaotic Sequence Generation

Threshold function

Bit XOR

Decrypted secret message

x = u*x(1-x)

(D/255)< x < (D+1)/255

Dij = Eij(bitxor)D

u = 3.9999x = 0.43125

Performance analysis

The performance of the technique will be

evaluated by,

Mean Square Error

Peak signal to noise Ratio

Correlation coefficient

Parameters:

Correlation Coefficient: It is used to find the similarity

between two different frames with their intensities. It will

be described by,

Cor_coef = [sum(sum(u1.*u2))] /

[sqrt(sum(sum(u1.*u1))*sum(sum(u2.*u2)))];

Where, u1 = F1 – mean of F1, u2 = F2 – mean of F2

F1 – Cover Frame and F2 – Encrypted Frame

Continues….

PSNR (Peak Signal to Noise Ratio)

MSE (Mean Square Error)

Where,

M,N are Number of Rows and Columns

aij – Input Image and bij –Embedded Image

Sample Text Encryption and Recovery

Input Text : hjfkdltige

Cipher Text : Mâejn4'

Decryption Text : hjfkdltige

Performance Metrics:

Mean Square Error: 0.0062

Peak Signal to Noise Ratio: 70.1890 dB

Correlation: -6.8914e-004

Elapsed time: 5.2649 Sec

Advantages

• It avoids the leaks of video content in storage of clouds

• Reduced time consumption process

• It is useful to perceive video tampering

• Better compatible system for people privacy protection

Recap

• The paper presented that protection of Video quality and

hidden data during transmission based on approach of

H.264 encoding and chaotic crypto system with bit

wrapping based data concealment

• h.264 encoding method is used for compress the video

frames effectively and chaos encryption was used as to

protect image contents

• The same method is used at the receivers end in order to

retrive the secret message back.

THANK YOU