A NEW PROPOSED SYMMETRIC KEY ALGORITHM FOR MODERN CRYPTOGRAPHIC

IJSRD - International Journal for Scientific Research & Development| Vol. 2, Issue 08, 2014 | ISSN (online): 2321-0613
All rights reserved by www.ijsrd.com 302
A New Symmetric Key Algorithm for Modern Cryptography
Rupesh Kumar1
Sanjay Patel2
Purushottam Patel3
Rakesh Patel4
1,2
Students 3,4
Lecturer
1,2,3
Department of Computer Science & Engineering 4
Department of Information Technology
1,2,3,4
Kirodimal Institute Of Technology, Raigarh, Chhattisgarh, India
Abstract— Communication in any language between two or
more persons is like a plaintext or simple text. That means
any person knowing that language can easily understand this
plain text until this plaintext is codified in some manner. So,
it is important to implement the coding techniques to ensure
that information is hidden from everyone for whom it is not
intended. So, that only authenticated person will be allowed
to access the information. Cryptography is the art and
science of achieving security by the encoding of messages in
an unreadable form. Cryptography derives from the Greek
word; the word “crypto” comes from kruptos, which means
"hidden” and graphy means “writing”. Thus, Cryptography
is the practice and study of the hiding messages. Today, the
cryptography is considered as branch for both the Computer
Science and mathematics, which will related to the
information theory.
Keywords: Cryptography, Symmetric Key Algorithms,
Network Security
I. INTRODUCTION
Today the whole world goes after the internet, which
provides essential communication and information between
thousands of people, and is being increasing in the aspects
of the commerce, education, entertainment and many more.
So, the security becomes an important issue to deal with it.
There are many aspects to the security and many
applications, ranging from secure commerce, payment to
private communication and protecting password.
One important aspect towards the security is the
Cryptography. The admiring concept of securing the
messages through the cryptography has a historical record.
In ancient times, When Julius Caesar sent messages to his
generals, he didn't trust his messengers. So he replaced
every A in his messages with a D, every B with an E, and so
on through the alphabet. Only someone who knew the “shift
by 3”rule could decipher his messages.
Cryptography is the science of using the concepts
of mathematics to encrypt and decrypt the information; also
it refers to art and science of designing the ciphers.
Cryptography enables you to transmit or receive the
sensitive information through an internet so that no one can
access the information. Since, the cryptography is the
science of securing the information, Cryptanalysis is the art
and science of breaking the secure information and
Cryptology involves both the cryptography and
cryptanalysis. [1]
Cryptographic algorithms and protocols can
be grouped into four main areas:
 Symmetric encryption: Used to conceal the
contents of streams of data of any size, including
message files, encryption keys and password.
 Asymmetric encryption: Used to conceal the
contents of stream of data, such as encryption keys
and hash function values, which are used in digital
signatures.
 Data integrity algorithms: Used to protect streams
of data, such as message from alteration.
 Authentication protocols: These are schemes based
on the use of cryptographic algorithms designed to
authenticate the identity of entities.
A Cryptographic algorithm is a mathematical
functions used in the process of encryption and decryption.
A cryptographic algorithm works in combination with a key
– a word, number or phrase – to encrypt the plaintext. With
the help of these keys this plain text is converted into
ciphertext (an unreadable form). The security of the
encrypted messages will depend up on the strength of the
cryptographic algorithm and the secrecy of the key. A
cryptographic algorithm, plus all possible keys and all the
protocols that make it work comprise a cryptosystem.
Without the use of decryption keys, the ciphertext cannot be
converted into its plaintext.
There are two basic types of cryptography:
Symmetric Key and Asymmetric Key. In symmetric (also
called "private key") encryption, the same key is used for
both encryption and decryption. In asymmetric (also called
“public key") encryption, one key is used for encryption and
another for decryption. A new Symmetric Key
cryptographic algorithm has been proposed in this paper
with its advantages
II. CRYPTOGRAPHY
The information can be read and understand without taking
special steps will be considered as plain text. So it is
necessary to hide the plaintext into some non- readable
form. The process of hiding the contents of the plain text
into some non-readable form i.e. ciphertext is called an
encryption. The process of getting the plain text from the
cipher text again is called the decryption as shown in figure.
Fig. 2.1: Process of Encryption and Decryption
Generally, where cryptography is used, two parties
(A and B) communicate over insecure channel (internet).
They want to ensure that the exchange of information
between them is secure or incomprehensible so that, anyone
who might listening their conversation will not be able to
understand. Since A and b are in remote locations, therefore

(IJSRD/Vol. 2/Issue 08/2014/069)
A also want to ensure that the information would not be
modified by anyone (attacker) as the same information will
be received by B as it is transmitted by A himself.
Furthermore, B also want to ensure that the data should be
transmitted by A not by anyone else. Thus, cryptography is
used to achieve the following goals:
A. Data Confidentiality
With respect to the transmission of information over an
unsecure channel i.e. internet, the information may not be
secure. To ensure the security or privation of information
during the transmission, the confidentiality of data should be
necessary. Confidentiality is the protection of transmitted
information from passive attackers. The data confidentiality
can be achieved during the process of encryption.
Encryption is the process of converting the plain text into
cipher text. The security of data depends up on the strength
of the encryption algorithm and the secrecy of the key and
the equivalent decryption algorithm is used to convert the
cipher text into plain text. In symmetric key algorithm only
one key is used to encrypt or decrypt the text while in
asymmetric key two different keys are used to encrypt or
decrypt the text.
B. Data Integrity
Integrity means to impose the sets of rules and regulations.
As with data confidentiality, integrity can apply to a stream
of messages or a single message. There are two ways to
impose the integrity: first one for connection oriented
integrity service, if A send the stream of messages, and then
he wants to ensure that the message will be received by B as
sent, so that there will no modification, insertion, replays or
duplications. The benefits of the integrity are that the
destruction of data will be recovered. Second one for
connectionless integrity service, one deal with individual
messages without regard to any larger context, provides
protection against only the modification. The verification of
the integrity is done by the hash values. A hash value has a
fixed length which is derived from the sequence of the data.
To check the alteration of data, the hash values of the
received data will be compared to the hash values of the data
sent.
C. Authentication
The authentication is done to ensure that the communication
or the exchange of the information is done by particular
parties. The authentication should be provided by the digital
certificate. In case of a single message, the role of the
authentication service is to ensure the recipient that the
message is from the source that it claims to be from. There
are two types of specific authentication services are defined
in X.800: (I) Peer entity authentication and (II) Data origin
authentication.
D. Nonrepudication
The nonrepudication prevents either sender or receiver from
denying the transmitted messages. Thus, when a message is
sent by A, then the B can know that, A in fact transmitted
the message to B. Similarly when a message is received by
B, then the A can know that the B in fact received the
message, by sending an acknowledgment data.
III. TYPES OF CRYPTOGRAPHY
Cryptography involves the process of scrambling the
plaintext into the ciphertext and vice-versa. The process of
conversion of plain text into cipher text is called an
encryption and the process of conversion of ciphertext into
plaintext is called decryption. There are several ways to
classify the cryptographic algorithm, but there are two most
successful algorithms: (I) Symmetric key cryptographic
algorithm and (II) Asymmetric key cryptographic algorithm.
In symmetric key cryptographic algorithm only one key is
used to encrypt or decrypt the data, while in Asymmetric
key cryptographic algorithm two different keys are used,
one key is used for the process of encryption, and other will
be used for the process of decryption. Figure 3.1 shows the
types of the cryptographic algorithm.
Fig. 3.1: Types of Cryptography
A. Symmetric key cryptography
It is also known as the secret key cryptography, in which
only one key is used for both processes. The sender uses
single key to encrypt the plaintext into the ciphertext, after
the process of conversion of ciphertext from the plaintext.
Then the receiver will use same key to decrypt the cipher
text to get the plain text as shown in figure below. With this
approach of the cryptographic algorithm the key should be
known to both sender and receiver. The main disadvantage
in this is the distribution of the key.
Fig. 3.1.1: Symmetric Key Cryptography
B. Asymmetric key cryptography
It is also known as a public key cryptography, in which two
different keys are used to encrypt or decrypt the
information, one key is used for the encryption process
while the other one is used for the decryption process. In
asymmetric key cryptography, the sender uses the public
key for the encryption of the plain text, so that the other
users will encrypt the data using the copy of the public key

but they are not allowed to decrypt it. The receiver has the
private keys so that he can decrypt it as shown in below
figure. The main advantages of using the asymmetric key
are that allows the preexisting users to exchange the
information securely.
Fig. 3.2.1: Asymmetric Key Cryptographic
IV. SYMMETRIC KEY CRYPTOGRAPHY
Generally the private key cryptography or secret key
cryptography is categorized as a block cipher or a stream
cipher. A stream cipher is that which operates on the single
bit or single byte at a particular time. In this approach, as
shown in figure 4.1, the bit stream generator is a key
controlled algorithm and produce a bit of stream i.e.
cryptographically strong. The examples of the stream
ciphers are the autokeyed vigenere and the vernam ciphers.
A block cipher is that which operates on the block of the
plaintext to produce a ciphertext block having equal length.
Generally, a block size of 64 or128 bits will be used. As
with a stream cipher, the two users share a symmetric
encryption key, as shown in figure 4.2. Using some modes
of operation, a block cipher can be used to achieve the same
effect as a stream cipher.
Fig. 4.1: Stream cipher using algorithm bit stream generator
[2]
A block cipher operates on a plaintext block of n
bits to produce a ciphertext block of n bits. There are 2n
possible different plaintext blocks and for the encryption to
be reversible (for decryption to be possible), each must
produce a unique ciphertext block. Such a transformation is
called reversible, or nonsingular.
Feistel proposed [FEIS73] that we can approximate
the ideal block cipher by utilizing the concept of product
cipher, which is the execution of two or more simple ciphers
in the sequence in such a way that the final result or product
is cryptographically stronger than any of the component
cipher. The essence of the approach is to develop a block
Fig. 4.2: Block ciphers
cipher with a key length of k bits and a block
length of n bits, allowing a total of 2k
possible
transformations. Generally, Feistel proposed the use of a
cipher that alternates substitutions and permutations.
Substitution: Each letter of the plaintext is
uniquely replaced by the corresponding ciphertext letters.
Permutation: A sequence of the plaintext letters is
replaced by permutations of that sequence. That is, no letters
are added or removed or replaced in the sequence.
V. KEYS
A key plays an important role in providing the security on
the information transmitted over the unsecure channel. The
key is value which will combines with the cryptographic
algorithm in a plain text to produce a ciphertext. The
security of data to be transmitted depends on the strength of
the cryptographic algorithm and the secrecy of the key. If
the has larger values, then the security will be more.
Generally, there are two types of keys are used in
cryptography: (I) Symmetric key and (II) Asymmetric key.
In symmetric key cryptographic algorithm only one key is
used to encrypt or decrypt the data, while in Asymmetric
key cryptographic algorithm two different keys are used,
one key is used for the process of encryption, and other will
be used for the process of decryption.
Larger keys will be cryptographically secure for a
longer period of time. In public key cryptography, the bigger
the key, the more secure the ciphertext. While the public and
private keys are mathematically related, it’s very difficult to
derive the private key given only the public key. Keys are
stored in encrypted form. PGP stores the keys in two files on
your hard disk; one for public keys and one for private keys.
These files are called key rings.
VI. DIGITAL SIGNATURES
A digital signature provides an authentication mechanism
which enables the writer of a message to attach a code that
acts as a signature. The DSS (digital signature standard) is
an NIST standard that uses the secure hash algorithm
(SHA). A major benefit of the public key cryptographic is

that it provides a method of employing digital signatures.
The different, as shown in figure 6.1`.The digital signature
provides a set of security capabilities that would be difficult
to implement in any other way.
Fig. 6.1: Digital Signatures
The digital signatures has following properties:
 It must verify the author and the date and time of
signature.
 It must authenticate the contents at the time of the
signature.
 It must be verifiable by third parties, to resolve
disputes.
The digital signature has the following requirements:
 The signature must be bit pattern that depends on
the message being signed.
 It must be relatively easy to produce the digital
signature.
 It must be easy to recognize and verify the digital
signature.
 It must be practical to retain a copy of the digital
signature in the storage.
VII. NEW PROPOSED SYMMETRIC KEY ALGORITHM
This algorithm is easy to implement and more secure,
because there is two reversed operations present in this
algorithm which makes it more complex in nature. This
algorithm is very easy to learn and practice because the
steps followed in the process of conversion of the plaintext
into the cipher text is very simple and vice-versa.
A. Encryption algorithm
As we know that the encryption is the process of conversing
the plaintext into the ciphertext with the help of the
cryptographic algorithm and the secret key. The steps
followed in this algorithm are as follows:
Step1: Determine the ASCII value of the letter.
Step2: Determine the corresponding binary value of it.
[Binary value should be 8 digits e.g. for decimal 32 binary
number should be 00100000]
Step3: Reverse the 8 digits of the binary value.
Step4: Take a 4 digits divisor (>=1000) as the Key.
Step 5: Divide the reversed number with the divisor.
Step 6: Store the remainder in first 3 digits & quotient in
next 5 digits (remainder and quotient wouldn’t be more than
3 digits and5 digits long respectively. If any of these are less
than 3 and 5 digits respectively we need to add required
number of 0s (zeros) in the left hand side. So, this would be
the ciphertext i.e. encrypted text.
Now store the remainder in first 3 digits & quotient
in next 5digits.
B. Examples
Let, the character is “T”. Now according to the steps we will
get the following:
Step 1: ASCII of “T” is 84 in decimal.
Step 2: The Binary value of 84 is 1010100. Since it is not an
8 bit binary number we need to make it 8 bit number as per
the encryption algorithm. So it would be 01010100.
0 1 0 1 0 1 0 0
Step 3: Reverse of this binary number would be 00101010.
0 0 1 0 1 0 1 0
Step 4: Let 1000 as divisor i.e. Key.
Step 5: Divide 00101010 (dividend) by 1000(divisor).
Step 6: The remainder would be 10 and the quotient would
be 101. So as per the algorithm the ciphertext would be
01000101 which is ASCII 69 in decimal i.e. “E”.
0 1 0 0 0 1 0 1
C. Decryption algorithm
As we know that decryption is the process of conversing the
ciphertext into plaintext using the private key. The steps
followed in this algorithm are as follows:
Step 1: Multiply last 5 digits of the ciphertext by the Key.
Step 2: Add first 3 digits of the ciphertext with the result
produced in the previous step.
Step 3: If the result produced in the previous step i.e. step 2
is not an 8-bit number we need to make it an 8- bit number.
Step 4: Reverse the number to get the original text i.e. the
plaintext.
D. Examples
After encrypting “T” we got 01000101 as the ciphertext. So,
after decrypting this ciphertext into its plaintext, we have to
get “T”.
Now follow the steps of the decryption algorithm:
Step 1: After multiplying the last 5 digits of the ciphertext
i.e. 00101 by 1000 (Key), the result would be 101000.
1 0 1 0 0 0
Step 2: After adding 010 (first 3 digits of the ciphertext)
with
101000 the result would be 101010.
1 0 1 0 1 0
Step 3: Since 101010 is not an 8-bit number we need to
make it 00101010.
0 0 1 0 1 0 1 0
Step 4: After reversing the number it would be 01010100
i.e.ASCII 84 in decimal i.e. “T” as character which was the
original text.

0 1 0 1 0 1 0 0
E. Advantages
 This algorithm is easy to learn and implement.
 This algorithm is more secure because there will be
two reverse operations in it which provides
complexity.
 For small amount of data, this algorithm will be
very useful because it takes less time to encrypt it.
VIII. CONCLUSION
To provide security of the information or the data
confidentiality, or the data integrity, or the authentication, or
the nonrepudilication, cryptography is the best method for
implementing it. Since, cryptography is the art and science
of hiding the original form into some other form. In order to
achieve these goals, various cryptographic algorithms are
developed. For a small amount of data or information to be
encrypted, there should be efficient way to produce the
ciphertext in a minimum cost. The main aim of this paper is
to develop the new symmetric algorithm to produce the
ciphertext for the small amount of information. By doing so,
we can save our time and provide the security in data
transmitted. As we know that the public key is more secure
and advantages over the private key algorithm or the
symmetric key cryptographic, therefore our next task is to
find a new and simple public key cryptographic algorithm.
REFERENCES
[1] Cryptography and network security, 5th
edition
William Stallings
[2] Cryptography and network security, online
publication, 5th
edition William Stallings
[3] Computer and Network security by Atul Kahate.
[4] Fundamentals of Computer Security, Springer
publications “Basic Cryptographic Algorithms”, an
article available at
www.itsc.state.md.us/oldsite/info/InternetSecurity/
Crypto/CryptoIntro.htm#Algorithms.
[5] “A Brief History of Cryptography”, by S. Hebert

A NEW PROPOSED SYMMETRIC KEY ALGORITHM FOR MODERN CRYPTOGRAPHIC

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A NEW PROPOSED SYMMETRIC KEY ALGORITHM FOR MODERN CRYPTOGRAPHIC