1. CRYPTOGRAPHY

2. TOPICS OF SEMINAR Introduction & Related Terms Categories and Aspects of cryptography Model of Network Security Encryption Techniques Public key cryptosystem Application Bibliography

3. DEFINATION OF CRYPTOGRAPHY Cryptography is the study of mathematical techniques related to the aspects of information security, such as confidentially, data integrity and entity authentication. Cryptography is not only means of providing information, but rather one set of techniques.

4. Related Terms Plain text :-Original Message Cipher text:-Coded Message. Encryption:-The process of converting plain text into cipher text. Decryption:-Restoring plain text from cipher text.

5. Cryptography:-The science or area of Encryption & Decryption Cryptanalysis:-The science of analysis or breaking of secure communication Cryptology :- The area of cryptography and cryptanalysis together

6. Categories OF CRYPTOGRAPHY There are two types of cryptographic algorithm Symmetric key Asymmetric key

7. GOALS OF CRYPTOGRAPHY Confidentially Data Integrity Authentication Non-repudiation

8. ASPECTS OF SECURITY Security Service Security Mechanism Security Attacks Passive Attacks Active Attacks

9. MODEL OF NETWORK SECURITY

10. There are four basic tasks in designing a particular security services. Design an algorithm Generate a secret information Develop methods for distribution and sharing Specify the protocol

11. SUBSTITUTION TECHNIQUES CAESAR CIPHER To Encrypt using Caesar's key value of 3,we offset the alphabet so that the 3rd letter down (D) begins the alphabet. ABCDEFGHIJKLMNOPQRSTUVWXYZ and sliding everything up by 3, you get DEFGHIJKLMNOPQRSTUVWXYZABC where D=A, E=B, F=C, and so on. "SECRET" encrypts as "VHFUHW."

12. TRANSPOSITION TECHNIQUES Plain text = “meet me after this party” Key = 2 m e m a t r h s a t e t e f e t i p r y Cipher text =“mematrshsatetefetipry”

13. A more complex scheme is Key 4 3 1 2 5 6 7 plaintext: a t t a c k p o s t p o n e d u n t I l t Ciphertext: TTNAPTTSUAODCOLKNLPET

14. DES ALGORITHM

15. Public Key Cryptosystem: Secrecy Encryption Algorithm Source A Source Destination Decryption Algorithm Key pair source Cryptanalyst Destination B B’s public keyB’s private key

16. Public Key Cryptosystem: Authentication Encryption Algorithm Source A Source Destination Decryption Algorithm Key pair source Cryptanalyst Destination B A’s private key A’s public key

17. Public Key Cryptosystem: Secrecy & Authentication Encry. Algori- them Encry. Algori- them Decry. Algori- them Decry. Algori- them Sourc e Dest. Key Pair Source Key Pair Source B’s private key B’s public key A’s public key Source A Destination B A’s private key

18. APPLICATION Secure Communication Identification & Authentication Secret Sharing

19. BIBLIOGRAPHY Cryptography & Network Security By William Stallings WWW.google.com Computer Network By Andrew S. Tanenbaum

20. THANK YOU