1. Public Key Encryption

2. Introduction The Problem Network security Public Key Encryption
Encryption/Decryption
Public Key Encryption
How is data transmitted?
Secure Socket Language
Conclusion
Questions and Comments

3. The Problem Trough the Internet, people can: Buy products online
Buy services online
Do bank transactions online

4. The Problem Threats to network security include: Data diddling
Salami attack
Piggybacking
Denial of Service (DoS)
Distributed Denial of Service (DDoS)

5. The Problem
Several network security schemes have been developed and used throughout the years

6. Network Security Protection alternatives include: Use of passwords
Use of security modems
Encryption/decryption methods

7. Encryption / Decryption
Network Security
The most secure protection methods are those which use
Encryption / Decryption

8. History Network Security Used since Roman Empire
Used by governments for military purposes
Nowadays it is being performed by computers

9. Encryption / Decryption
What is encryption/decryption?
Network Security
Encryption / Decryption
"Enryption is the translation of data into a secret code."

10. Transposition Algorithm
What is encryption/decryption?
Network Security
Transposition Algorithm
An example

11. Network Security Key = PUBLIC P U B L I C 5 6 1 4 3 2
What is encryption/decryption?
Network Security
Key = PUBLIC P U B L I C 5 6 1 4 3 2

12. Public key encryption is secure now
What is encryption/decryption?
Network Security
Message to send:
Public key encryption is secure now

13. Network Security 5 6 1 4 3 2 P U B L I C K E Y E N C R Y P T I O N I S
What is encryption/decryption?
Network Security 5 6 1 4 3 2 P U B L I C K E Y E N C R Y P T I O N I S S E C U R E N O W B Y P

14. Network Security The message will now be …
What is encryption/decryption?
Network Security
The message will now be …
BYPSE CCOCF INIEF LETSF PKRNU UEYIR
Unauthorised users who do not have the key will not be able to convert it back to the original message

15. What is encryption/decryption?
Network Security
A key or password is necessary for encryption and decryption.
Decryption is the changing back of encrypted code (or cipher text) to plain text.

16. What is encryption/decryption?
Network Security

17. What is encryption/decryption?
Network Security
There are two main types of encryption / decryption security measures:
Public Key Encryption (Asymmetric)
Symmetric Key Encryption

18. Public Key Encryption Network Security Uses two keys: Public Private
Public Key (Asymmetric) Encryption
Network Security
Public Key Encryption
Uses two keys:
Public
Private
A popular implementation is the SSL (Secure Socket Layer)

19. Symmetric Key Network Security Uses only one key
Symmetric Key Encryption
Network Security
Symmetric Key
Uses only one key
Key must be known only by the sender and receiver
Faster encryption/decryption

20. Public Key Encryption History
First invented in early 1970s by Clifford Cocks.
Reinvented by Rivest, Shamir and Adleman in 1976 and was called RSA. It was published.
In 1984 ElGamal created his algorithm.
In 1989 Koblitz created his hyperelliptic curve cryptography algorithm

21. How is data sent using public key encryption?
Sender encrypts the message using its private key
Sender encrypts its private key using the receiver’s public key
Receiver uses its private key to decrypt the sender’s private key
Receiver uses the sender’s private key to decrypt the message.

23. Digital signatures
Public Key Encryption
Authentication is also done using digital signatures.
Digital signatures are sent to the receiving computer to make sure that the sender is who it says it is.

24. Public Key Encryption Digital certificates are used.
A large scale
Public Key Encryption
Digital certificates are used.
Before communication starts the certificate authority confirms that every computer is who it says it is.

25. Public Key Encryption Hashing algorithms are used to create keys.
A simple example:
Input
number
Hashing
Algorithm
Hash
Value
32,569
Input # x 138
4,494,522

26. Hashing algorithms
Public Key Encryption
If the algorithm is not known, it is very difficult to determine the input number.
In reality more complex numbers are used, usually 40-bit or 128-bit

27. Public Key Encryption Checks for data corruption
Validation and Verification of data
Public Key Encryption
Checks for data corruption
Two popular algorithms:
Checksum
Cyclic Redundancy check (CRC)

28. Public Key Encryption An implementation of Public key encryption
Secure Socket Layer (SSL)
Public Key Encryption
An implementation of Public key encryption
Developed by Netscape
Used extensively by Netscape and Internet explorer

29. Secure Socket Layer (SSL)
Public Key Encryption
URL of an SSL-enabled website starts with
An example is the Go Mobile page for topping up your mobile credit

30. Secure Socket Layer (SSL)
Public Key Encryption
It has become part of the transport layer in the OSI Model
Is known as the TLS (Transport Layer Security)

31. Public Key Encryption Sender creates a private key
What happens in an SSL?
Public Key Encryption
Sender creates a private key
Sender sends it to the receiving computer using the receiver’s public key

32. What happens in an SSL?
Public Key Encryption
Communication is then encrypted/decrypted using the private key
After communication between the two computers ends the key is discarded

33. Conclusion
The most common protection alternatives used are those that use the encryption/decryption methods.
Encryption is the translation of data into a code that is not understandable without the key.
Decryption is the changing back of code from cipher text to plain text.
A key or password is necessary.

34. Conclusion There are two types:
Public key encryption
Private / Symmetric key
Private key encryption uses only one key, which is private.
Public key encryption uses two keys:
Public key
Private key

35. How is data sent using public key encryption?
Conclusion
How is data sent using public key encryption?

36. Conclusion Authentication is done using digital signatures
Digital certificates are used in a large scale communication
Hashing algorithms are used to create keys and passwords.
Checksum and CRC are used to check for data corruption

37. Conclusion SSL is an implementation of public key encryption.
Private keys are created before every communication session, and deleted afterwards

38. For notes and references for further reading
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For notes and references for further reading