This document discusses cryptographic techniques used for secure communication. It defines cryptography as the art of secret coding to provide confidentiality, integrity, authentication, and non-repudiation. The two main techniques are symmetric encryption, which uses a shared secret key, and asymmetric encryption, which uses public and private key pairs. Common symmetric algorithms discussed are AES, DES, and Blowfish, while asymmetric algorithms include RSA and Diffie-Hellman key exchange. The goal of cryptography is to provide security services like confidentiality, integrity, authentication, non-repudiation, availability, and access control.

1. A STUDY ON CRYPTORAPHIC
TECHNIQUES
GROUP1

2. Introduction
• All works related to banking, ATM card, credit card, marketing, E-
commerce etc. are being done with the aid of internet. So there must
be protection provided over the network.
• Therefore, to secure communication several cryptography techniques
are used. We apply these cryptographic techniques to sensitive
information in order to provide protection from an unauthorized
access.

3. Definition
• Cryptography is the art of secret coding. The basic service provided by
cryptography is the ability to send the information between
participants in a way that prevents others reading it.
• The main purpose of the cryptography is used not only to provide
confidentiality, but also to provide solutions for other problems like:
data integrity, authentication, non-repudiation.
• The cryptographic technique and various algorithms are used to
ensure the application has the necessary security. Cryptography is the
science of both encryption and decryption.

4. Cont.
• Cryptography is the science of both encryption and decryption.
• Cryptography is a technique that masks the data over the channel of communication.
• Hiding the data to outsiders is an art. Several schemes are used for secure
communication.
• The cryptographic technique and various algorithms are used to ensure the application
has the necessary security.
• Application of these cryptographic techniques to sensitive information in order to
provide protection from an unauthorized access. In cryptosystem, data are protected
via encryption method for keeping communication is private.

5. GOAL OF CRYPTOGRAPHY
Non-repudiation: It is the process of preventing the sender from refusing the
message being sent.
Authentication: It is the process of ensuring the identity of the users
connected in the network. It responds to the question “Who can send the
message”.
Integrity: It is the process of securing the message from changes while in
transmission.

6. Cont.
Confidentiality: It is the process of assuring the intended users that no
middleman can view the content of the message. It responds to the
question “who can see the message”.
Availability: It is process of confirming the presentence of data in the
storage for future references.
Access control: It has a list of users with their rights to access the file.

7. Key terms
• Plain text: Original message is known as plain text.
• Cipher text: Coded message is known as cipher text.
• Encryption: The process of converting the plain text to cipher text is known
as encryption.
• Decryption: The process of restoring the plain text from the cipher text is
known as decryption.
• Key: A secret like a password used to encrypt and decrypt information.
There are a few different types of keys used in cryptography.
• Steganography: It is actually the science of hiding information from people
who would snoop on you.

8. SUBSTITUTION AND TRANSPOSITION TECHNIQUE
• Substitution technique and Transposition technique are the types of
operation used for converting plain text into cipher text.
• A substitution technique is one in which plain text letters are replaced with
other letters, numbers or symbols whereas In Transposition Technique the
plaintext letters perform some kind of permutation.

9. CRYPTOGRAPHIC TECHNIQUES
• There are two basic information encryption techniques:
• Symmetric encryption, which is also called secret key encryption, and
asymmetric encryption, also called public key encryption.
A. Symmetric-key cryptography: refers to methods of encryption, in which
the sender and the receiver share the same key. Symmetric key ciphers are
either used as block ciphers, or as stream ciphers.

10. Cont.
• A block cipher enciphers the input type used by a stream cipher, in
plaintext blocks as opposed to individual characters. Symmetric
cryptography is much faster than asymmetric.

11. Cont.
• This is the simplest method of encryption, requiring only one secret
key for ciphering and deciphering information.
• Examples of symmetric encryption include:
• DES(Data Encryption Standard )
• TDES(Triple Data Encryption Standard ),
• AES(Advanced Encryption Standard),
• Blowfish, etc.

12. Cont.
• Advanced Encryption Standard (AES)
• AES is a variable bit block cipher that uses the 128, 192 and 256-bit
variable key range. If both the length of the block and the length of
the key are 128 bits, AES will do 10 rounds of processing.
• If the block and key are 256-bit long then 14 processing rounds are
performed.
• AES is a symmetrical block cipher capable of blocking size128bit,
128,192 and 256-bit cipher keys.

13. Cont.
• DES(Data Encryption Standard )
• This was the most commonly used standard worldwide.
• It is a block cipher that encrypts a plaintext of 64 bits at a time and
uses 56 bit key. This was based on symmetric key algorithm which
means that both encryption and decryption will use the same key.
• DES has 16 rounds, meaning that cipher text is generated using a total
of 16 processing steps on the plaintext input.

14. Cont.
• First, 64 bit data is passed through the initial permutation phase and
then 16 processing rounds are performed
• Finally the final permutation step is performed on the plain text input
which results in 64 bit cipher text.
• The drawback of this algorithm is that by adding all possible
combinations it can be easily vulnerable to Brute Force Attack in
which the hacker tries to crack the key.

15. Cont.
• Triple Des (TDES)
• TDES uses DES encryption in three rounds and has a key length of 168
bits (56*3).
• The Encrypt Decrypt-Encrypt (EDE) series uses either two or three 56
bit keys.
• The drawback of this algorithm is that it consumes too much time

16. Cont.
Blowfish
• Blowfish algorithm is the important form of symmetric key encryption
which has a block size of 64 bit and a key length variable of 32 bits to
448 bits in general.
• It is based on a network of 16 round fiestel cipher, using the large key
size. The key size is bigger, as the code in the blowfish algorithm is
hard to break.
• However, apart from the low main class attack, it is exposed to all of
the attacks.

17. Cont.
B. Asymmetric Encryption
• Asymmetric key cryptography refers to methods of encryption, in which the
sender and the recipient share the same key.
• Asymmetric Encryption is a relatively new and complex Encryption style.
Complex, because it uses two cryptographic keys for data security
implementation.
• Asymmetric encryption is also known as public key cryptography, opposed to
symmetric encryption, which is a relatively new technique. For asymmetric
encryption, two keys are used to encrypt a plain text. Examples include RSA
and DH

18. RIVEST-SHAMIR-ADLEMANAND DH( DIFFIE-
HELLMAN) (RSA)
• RSA is one of the first functional cryptosystems with a public key and is
commonly used for securedata transmission The encryption key is available in
such a cryptosystem, which varies from the decryption key that is kept secret.
• Diffie-Hellman key exchange, also known as exponential key exchange, is a
digital encryption system that uses numbers raised to specific powers to
generate decryption keys based on components that are never transmitted
directly, thereby mathematically overcoming the task of a would-be code
breaker.

19. Conclusion
• Cryptography is a very interesting field in computer science area
because the amount of work done is only kept secret.
• There are various techniques and algorithm studied and different
types of research have been done.
• The best algorithms are those which are well documented and well
known because the algorithms are well tested and well-studied.

20. References
• International Journal of Scientific Research in Computer Science,
Engineering and Information Technology
• ISSN : 2456-3307 (www.ijsrcseit.com) doi :
https://doi.org/10.32628/CSEIT206453
• CSEIT172150 | Received: 20 Feb 2017 | Accepted: 28 Feb 2017 | January-
February-2017 [(2)1: 249-252] International Journal of Scientific Research
in Computer Science, Engineering and Information Technology © 2017
IJSRCSEIT | Volume 2 | Issue 1 | ISSN : 2456-3307
• https://www.academia.edu/33111881/Study_on_Cryptography_and_Tech
niques
• International Journal of Innovative Research in Science,
Engineering and Technology(An ISO 3297: 2007 Certified Organization)Vol.
5, Issue 3, March 2016