Cryptography is the practice of hiding information to store or communicate it in a secure way. It allows for confidentiality, integrity, and authentication of messages. There are two main types: symmetric key cryptography which uses a single key for encryption and decryption, and asymmetric key cryptography which uses different public and private keys. Popular symmetric algorithms include AES and DES, while RSA is an example of an asymmetric algorithm. The seminar discussed the components, processes, and applications of cryptography as well as examples of algorithms and common attacks.

1. Seminar
On
CRYPTOGRAPHY
Presented by:
Durlab Kumbhakar

2. What is Cryptography?
 Cryptography derived its name from the Greek words called
“krypto’s” which means “Hidden or Secrets” and “graphein”
which means “Writing or Study.”
 Cryptography is the practice and study of hiding information or
secret writing. It is the Art or Science of converting a plain
intelligible data into an unintelligible data and again
retransforming that message into its original form.
 It provides Confidentiality, Integrity, and Accuracy.

3. Purpose of Cryptography
 Privacy/confidentiality: Ensuring that no one can read the
message except the intended receiver.
 Integrity: Assuring the receiver that the received message has
not been altered in any way from the original.
 Non-repudiation: A mechanism to prove that the sender
really sent this message.

4. Component of Cryptosystem
• Plaintext
• Encryption Algorithm
• Ciphertext
• Decryption Algorithm
• Encryption Key
• Decryption Key

5. Encryption and Decryption
plaintext
message
ciphertext
message
Encryption
Decryption

6. Types of Cryptography
Two types of Cryptography is available
1. SYMMETRIC KEY CRYPTOGRAPHY
2. ASYMMETRIC KEY CRYPTOGRAPHY

7. • Single key used to encrypt
and decrypt.
• Key must be known by both
parties.
• Assuming we live in a
hostile environment, it may
be hard to share a secret key..
• Examples of popular
symmetric algorithms
include DES, 3DES,
AES, Blowfish, etc.
1. Symmetric Key Cryptography

8.  Different keys are used to
encrypt and decrypt the
information.
 Each entity has 2 keys:
Private Key (a secret)
Public key (well known); one
key is used for encryption, the
other can decrypt the ciphertext
back to the original plaintext.
Examples of popular Asymmetric
algorithms include RSA, DSA, etc
2. Asymmetric Key Cryptography

9. TYPES OF CRYPTOGRAPHIC ALGORITHMS

10. 3DE
S
• DES (the data encryption standard) is a symmetric block cipher.
The algorithm uses a 56-bit key to encipher/decipher a 64-bit block
of data. The key is always presented as a 64-bit block, every 8th bit
of which is ignored. However, it is usual to set each 8th bit so that
each group of 8 bits has an odd number of bits set to 1.
Use of multiple length keys leads us to the
Triple-DES algorithm, in which DES is
applied three times. If we consider a triple
length key to consist of three 56-bit keys
K1, K2, K3 then encryption and
decryption is beside the table:
.
Encryption Decryption( in
reverse of
Encryption)
• Encrypt with K1
• Decrypt with K2
• Encrypt with K3
• Decrypt with K3
• Encrypt with K2
• Decrypt with K1
DES: DATA ENCRYPTION
STANDARD

11. fig:- RSA1
RSA is a public key
algorithm invented by
Rivest, Shamir and
Adleman.
The key used for
encryption is different
from (but related to)
the key used for
decryption.
Algorithm is in fig:-
RSA1
RS
A

12. Hash functions
 Is a type of one-way function this are fundamental for much of
cryptography.
 A one way function - is a function that is easy to calculate but
hard to invert.
 It is difficult to calculate the input to the function given its output.
 The precise meanings of "easy" and "hard" can be specified
mathematically. With rare exceptions, almost the entire field of
public key cryptography rests on the existence of one-way
functions.

13. Applications of Cryptography
1. Defense Services
2. Secure Data Manipulation
3. E-Commerce
4. Business Transactions
5. Internet Payment System
6. Secure Internet Communication
7. Data Security
8. Secure Access to Corresponding data

14. Cryptographic Attacks
Ciphertext only attack
 The only data available is a target cipher text
Known plaintext attack
 A target cipher text
 Pairs of other cipher text and plaintext (say, previously broken or guessing)
Chosen plaintext attacks
 A target cipher text
 Can feed encryption algorithm with plaintexts and obtain the matching cipher
texts
and so many attacks available like Dictionary Attack, Timing Attacks etc.

15. CONCLUSION
 We use different types of algorithms to establish security
services in different service mechanisms.
 We use either private key cryptography or public key
cryptography according to requirement.
 If we want to send message quickly we use private key algorithm
and if we want to send messages secretly we use public key
algorithm.

16. References
 www.google.com
 en.wikipedia.org
 www.youtube.com
 www.tutorialspoint.com

17. Thank You