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Gautam Kumar Jha

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Computer Engineering

Thakur College of Engineering & Technology

Mumbai, India

[email protected]

Dr. R. R. Sedamkar

Computer Engineering

Thakur College of Engineering & Technology

Mumbai, India

[email protected]

Abstract—In
the recent trend, data are increasing enormously in day to day life.
Securing data is one of the main challenge nowadays, as data travels
through different medium where medium is not secured.
To
prevent confidential data from an unauthorized access there are
number of approaches. The methods of symmetric key cryptography and
asymmetric key cryptography can be used for encrypting and decrypting
the multimedia files.

This
paper mainly focuses on a proposed technique used for encrypting and
decrypting multimedia data through the hybrid proposed model based on
the assemblage of Advanced Encryption Standard and Deffie Hellman Key
Exchange Algorithm. The proposed method
generates a key by sender using Deffie Hellman algorithm and passed
to the AES algorithm which act as a key for encrypting multimedia
data. The encrypted data will be decrypted by the receiver key using
Deffie Hellman and AES.

The
advantage of this proposed hybrid model is that it will provide the
security to the multimedia data and also fill the gap of storage,
speed and security. It is even used for societal for communication of
data over network.

Keywords—
Security,
Multimedia, Cryptography, DES(Data Encryption Standard),
AES(Advanced Encryption Standard).
I.Introduction

In
a communication system, security of information is a major concern
nowadays. There are lots of techniques like hashing, stegnography,
cryptography that make available use for the safety of essential
information. Confidential data can be protected with the application
of Encryption and Decryption techniques as it takes an important
part. In the ancient times, through the study of past events the data
were made unreadable by scrambling the contents of information to
keep it secret. Cryptography algorithms like DES, AES, Blowfish, RSA
and Deffie Hellman provides higher level of security by using a pair
of key for both encryption and decryption.

AES
is a symmetric key algorithm where the plain text size is a block
size of 128,192,256 bit and the length of key is same as the size of
the plain text i.e. 128,192,256 bits. It involves basically four
steps as follows:

Byte
Substitution

Shifting
of rows

Mix
columns

Add
a round key

It
has total rounds of 10, 12 or 14 to encrypt data depending on the
plain text size of 128, 192 and 256 respectively. Initially bits are
converted into bytes. After which, data are substituted from the
substitution box and are arranged in a matrix form. In the further
step shifting of rows take place depending on the offset used i.e.
offset 0, offset 1, offset 2 and offset 3. Offset 0 means data will
remain on the same position where offset 1 means data will be shifted
by one position and respectively. In the next step columns are mixed
in a similar approach as of rows shifting. At the last, Addround key
is added after the mixing of columns and the process repeats till the
last rounds depending on the plain text size.

Deffie
Hellman is a key exchange algorithm, in which is keys are used for
communication to exchange data in a public network. It involves
basically five steps as follows:

Global
Public elements

User
‘A’ Key generation

User
‘B’ Key generation

Generation
of secret key by user ‘A’

Generation
of secret key by user ‘B’

Initially
the two global public elements are used one is a prime number element
and other is a primitive root of that prime number. In the next step,
user A selects a random number which is smaller than the prime number
and it is used as a private key. In the next step user B selects a
random number which is smaller than the prime number and it is used
as a private key. In the fourth step user B share his private key
with user A and then user A generates a secret key for exchanging
data. Similarly, user B generates a secret key for exchanging data.
In the last two steps we get the same result which is used as a
shared secret key.

The
result provided by Advanced Encryption Standard is much better and
faster than any other algorithm like Data Encryption Standard. Deffie
Hellman Key Exchange algorithm exchanges there private key and public
key to prepare a common shared key for exchanging the data. The
proposed hybrid algorithm is designed by combining AES and DHM to
encrypt the multimedia data by converting it into a bit equivalent to
reduce the overall time constraint and provide high level of
security.