Introduction to CNS

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