This document provides an overview of cryptography and network security. It discusses what cryptography is, the basic terminology used in cryptography like plaintext, ciphertext, encryption, algorithms and keys. It explains the two main types of cryptographic functions: symmetric key cryptography which uses a single shared key between sender and receiver, and asymmetric key cryptography which uses public and private key pairs. It also outlines two network security models - the model for network security and the network access security model.

1. Cryptography and Network
Security
Dr.S.Santhi
Professor
Department of ECE
KIT-Kalaignarkarunanidhi Institute of Technology

2. Agenda
What Is Cryptography?
Types of Cryptographic Functions.
Network Security Models.

3. Cryptography
• The art of secret writing.
The art of mangling information into apparent unintelligibility
in a manner allowing a secret method of unmangling.

4. Cryptography Definitions
• Messages:
– Plaintext
– Ciphertext
• Ingredients:
– Algorithm(s)
– Key(s)
• Players:
– Cryptographer: invents clever algorithms
– Cryptanalyst: breaks clever algorithms

5. Basic Terminology
• Plaintext: original message to be encrypted
• Ciphertext: the encrypted message
• Enciphering or encryption: the process of converting plaintext into
ciphertext
• Encryption algorithm: performs encryption
• Two inputs: a plaintext and a secret key

6. Symmetric Key Cryptography
• This private/secret/single key cryptography uses one key
• This key is shared by both sender and receiver
• if this key is disclosed communications are compromised
• It is also called symmetric, parties are equal
• It does not protect sender from receiver forging a message &
claiming is sent by sender

7. Asymmetric Key Cryptography
• It uses two keys – Private and Public key
• Asymmetric – Both sender and receiver use different keys
• It works by the clever use of number theory problems
• It complements rather than replaces private key cryptography

8. MODELS FOR NETWORK SECURITY
• Model for Network Security
• Network Access Security Model

9. Model for Network Security

10. Network Access Security
Model

11. Thank You