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  1. 1. 3rd Theorical Carmen Suárez Palomares Abraham José Silva Orozco Gabriela García CárdenasSunday, November 20, 11
  2. 2. Net working Devices interconnected Share information, files, and resources.Sunday, November 20, 11
  3. 3. NETWORKING A sending system: Segments -> adds header bytes Packets Protocol: 1) Format and Order -> Message exchanges 2) Actions taken of a messageSunday, November 20, 11
  4. 4. Socket Sockets allow the implementation of a client-server model. Communication must be started by one of the clients. The server waits for the client to start the communication. A socket is a process or an existing thread in the client and server machine, it allows the client and server to read and write information. !Sunday, November 20, 11
  5. 5. NETWORK CONNECTIONS 1. Fully connected network 2 2. Partially connected network 3. Hierarchical Network 4. Star Network 1 5. Ring Network 6. Multiaccess bus network (shared link) 7. Hybrid Networks 4 3 6 7 5Sunday, November 20, 11
  6. 6. Client-Server Clients connected to server Example: Accessing a web page Chat Client: Sends a demand or ! messages Server: Listen for incoming calls or messagesSunday, November 20, 11
  7. 7. Nachos Nachos/code/network -m 1 -o 0 Server (Buffer) Me ReceiverSunday, November 20, 11
  8. 8. PING Ping test the state of connection of Protocol host with one or others computers, sending package ICMP Ping works in the network layer, this use the encapsulate the message, in the package and then it sendSunday, November 20, 11
  9. 9. Example You Sister n.n Lost You Sister n.nSunday, November 20, 11
  10. 10. Ok, she is n.n n.n aliveSunday, November 20, 11
  11. 11. Pseudocode ///request Ping() ////answer ping.txt receive_request() validate() validate(request) verify structure if request = true{ execute() answer->send do ping->send } receive_ans(answer) validate() if answer = true{ echo “Connected” } else{ echo “Not Connected” }Sunday, November 20, 11
  12. 12. SECURITY Virus Malware Warms Zombies Trojans Others Botnets Funny DoSSunday, November 20, 11
  13. 13. Network Zombies & Botnets + = :( (Client-Server) ! !Sunday, November 20, 11
  14. 14. Important Points Sending Pings (easy) Server attacks Receive Information Broke elisa’s serverSunday, November 20, 11
  15. 15. Cryptography rap hy En c r y p t at i o t o g io n yp i t n Cr f in de f i n i t i o n de C = E( P, K e ) C i ph e r te x tSunday, November 20, 11
  16. 16. Cryptography De c r y p t i o n of f s’s de f i n i t i o n k h le e rc c i p K in P = D(C, K d) pr P l a i n te x tSunday, November 20, 11
  17. 17. Secret-key criptography Definition symmetric encryption Example In this example the plaintext HELLO would become the cyphertext SVOOL. All As are replaced by Zs, all Bs by Ys, all Cs by Xs and so on key Plaintext: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Ciphertext: Z Y X W V U T S R Q P O N M L K J I H G F E D C B A encryption key Monoalphabetic sustitutionSunday, November 20, 11
  18. 18. Secret-key criptographySunday, November 20, 11
  19. 19. Public-key cryptography ri v a te di f f e re n t k e ys y, p ke ) p ub lic e y ( k ic r n App l ic at i o n e t t io m a -A u t h e n t ic s: m pt at io n sy r y a c - D igi t a l S ig n at u re s en Prov ides: -Con fide ntia lity - Inte grit ySunday, November 20, 11
  20. 20. Public-key cryptographySunday, November 20, 11
  21. 21. Pseudocode a = “xxx”; b = encrypt_algorithm ke = encrypt_key t_encrypt = b ( a, key) t_encrypt = send ( ) receive ( t_encrypt) kd = decrypt_key if (kd == true){ t_decrypt = b (t_encrypt, kd) a = t_decrypt } else { print “you need the key to decrypt”Sunday, November 20, 11
  22. 22. Sunday, November 20, 11
  23. 23. References Chat application using Nachos Networking Module Uso de criptografía en aplicaciones Networking tutorial Protocolo ICMP Computer Networking - Kurose Ross Security technolifeandmore.blogspot.comSunday, November 20, 11