Curs 3
WebE‐mailForumFTPChatInstant messagingRSS feedsInternet TimeP2P
to browse = a rasfoiMosaic – primul browser grafic –1.0 – XI.1993Netscape 1.0 – 19944.5,4.79 – X.1998, XI.2001 7‐9 … Mozilla Firefox
Internet Explorer1.0 – 1995Curent: 7.0 (8.0 Beta)
Opera2.1 – XII.1996Curent: 9.6
Firefox Mozilla1.0 – XI.2004Curent 3.1
Google ChromeCurent 1.0 Beta
SafariApple ‐
Internet Explorer 7, 26.30%
Internet Explorer 6, 22.30%
Chrome, 3.10%
Firefox , 42.60%
Mozilla, 0.50%
Safari, 2.70%
Opera, 2.00%
Other, 5.20%
Utilizatori avansati
Internet Explorer , 72.22%
Firefox , 19.48%
Safari , 6.39%
Opera , 0.71%
Netscape , 0.68%
Chrome , 0.26%
Mozilla , 0.09%
Opera Mini , 0.05%Playstation , 0.04%Konqueror , 0.02%
Other, 1.85%
Total utilizatori
metoda de a scrie, trimite, receptiona si salva mesajeprin sinteme de comunicatii electronice“store and forward” – statia intermediara stocheazamesajul si il trimite destinatarului la cereremetoda asincrona de comunicareIstoric:
1971 – primul email trimis (ARPANET)1973 – email = 75% din traficul ARPANET1996 – 300 milioane mesaje/zi2001 – 9.8 miliarde mesaje/zi2008 – 210 miliarde mesaje/zi2008 – 1.3 miliarde utilizatori
corespunde existentei unui cont (username) pe un calculator (mailserver) care oferaservicii de email.Forma: username@mailserver@ = “at” (la)nu se accepta spatii si virgulamailserver: nume de (sub)domeniu sau IPconturile de cele mai multe ori au limitari in dimensiune totala a datelor
HeaderTO – adresa destinatar si numele destinataruluiSubject – un scurt text descriptiv al mesajului (deosebit de important)CC –Carbon CopyBCC – Blind Carbon Copy Data
BodyTextHTMLAtasamente: Attachments
Semnatura – 4÷9 linii de textLimita a dimensiunii totale: ~10MB
MIME: Multipurpose Internet Mail Extensions – ineficient
ProtocoalePOP3 – Post Office ProtocolIMAP – Internet Messages Access Protocol▪ webmailSMTP – Simple Mail Transfer Protocol
Spammesaje comerciale nesolicitatese estimeaza in prezent ca reprezinta 70‐75% din totalitatea mesajelorprobleme economice majore▪ stocare▪ fitrare▪ pierderea unor mesaje valide
Virusica atasamente a email‐uriloremail worms: se automultiplica prin intermediul email‐uluiToate sistemele antivirus moderne au capacitatea de a verifica un mesaj email inainte de a fi deschis
Securitatemesajele sunt in general necriptatemesajele trec prin mai multe gateway in drumul spredestinatar, pot fi interceptateMulti ISP pastreaza o copie locala a mesajelor inainte de a livra, de multe ori raman in “cache”SSL – Secure Sockets Layer SASL – Simple Authentication and Security Layer
Get Mail (check mail, get messages)Write (compose, new)ReplyForwardinlineas attachment
metoda sincrona de comunicareunele necesita un server care sa intermediezecomunicatiileclient – server – clientclient – client
IM – 1/1, paragrafYahooMicrosoftAOL
Chat – 1/x, paragrafTalk – 1/1, caracter
ServerClient 1
Client 2Client n
Yahoo Messengerhttp://messenger.yahoo.comemoticons☺ = :), = :(, ;‐) hidden emoticons: @};‐ , [‐O< , ^:)^
abrevieriAFAIK – as far as I knowBRB – be right backIIRC – if I recall correctlyIMHO – in my humble opinionLOL – laughing out loudROTFL – rolling on the floor laughingetc………
Chat asincronOrientate pedomeniuStructuraarborescenta(graf)Reguli(moderatori)Punct de intalnire pentrucei cu interesecomune
FTP – File Transfer ProtocolMetoda eficienta de transmitere a datelor binare (MIME – 66%)Aplicatie client – server
fisierele sunt incarcate pe un server care le stocheazaCont: username:password@serveranonymous:adresa_de_emailftp://numecont:[email protected] tipic: 21
SecuritateSSH – Secure ShellSFTP – SSH file transfer protocolSCP – Secure Copy Protocolport tipic: 22
AplicatiiBrowser‐eWinScpTotal Commander
RSS – Really Simple SyndicationFormat Web utilizat pentru a face disponibile utilizatorilor sau altorserver‐e informatii frecventmodificatestiripostari pe forum
P2P – peer to peerModalitate distribuita extrem de eficienta de punere in comun si transfer a datelor
Datele se gasesc pe calculatoarele clientServer‐ul mentine o listaTransferul se face direct intre clientiMai multi clienti simultan
AplicatiiKaazaTorrentEmuleDirect Connect
Notiuniswarmseedleech
Probleme de legalitate
Server n
Client n
Server 1
Client 1
Client 2
Client 3
Tipuri de dateMalwareCautare a informatiilorCriptare
WebHTML (.html, .htm, .asp, .php)suport – Cascading style sheets, Javascript (.css, .js)imagini
DateXML, RSSBinare (fisiere oarecare)Aplicatii▪ Java – limbaj interpretat▪ Active X (Internet Explorer)▪ Flash (.swf) –Adobe Flash Player▪ Silverlight (Microsoft)
DocumentePortable Document Format (.pdf) –Adobe Readeraltele
ImaginiDimensiunea extrem de importanta (90 ‐95 % din cantitatea de date web sunt imagini)Formate:▪ jpg – fotografii▪ gif – desene, animatie, transparenta▪ png – vectorial, transparenta
Multimedia – streamingAudio (CD 1411.2kbs, compresat 128‐320kbs)▪ mp3 – MPEG 1 Layer 3 ▪ wma –Windows Media Audio
Video▪ avi –Audio Video Interleave▪ wmv – Windows Media Video▪ swf
Malicious SoftwareVirus ▪ cod executabil▪ reproducere si distributie daca e lansat in executieWorm▪ reproducere si distributie prin transmisie activa prin reteaProfit▪ Spyware: aflare de informatii generale si comunicare peinternet
▪ Key logger: informatii confidentiale urmate de furt▪ Dialers: acces nedorit la servicii cu plata
Firewall si Antivirus activeFara click automat: Think before you click
www.google.com (71%)www.yahoo.com (18%)MSN/Live (5%)
RobotiBaza de dateServerClient
AND Si logicCuv_1 AND Cuv_2+ Cuv_1 +Cuv_2
OR Sau logicCuv_1 OR Cuv_2
NOT negare logicaCuv_1 AND NOT Cuv_2+ Cuv_1 ‐Cuv_2
NEAR apropiere in paginaCuv_1 NEAR Cuv_2
Fraza“Cuv_1 Cuv_2 …. Cuv_n”
Operator implicit ANDCuv_1 Cuv_2 = Cuv_1 AND Cuv_2
Folositi termeni neunivocifilm thin film technology
Incercati sa gasiti un termen care sa fie propriunumai informatiei cautate
Madonna – Like a prayer (versuri)Madonna – 91.500.000Madonna Prayer – 2.880.000+Madonna +Prayer – 2.580.000+Madonna +Prayer –religion – 98.500 +Madonna +”Like a prayer” – 818.000+Madonna +”Like a prayer” +lyrics – 144.000▪ Toate din primele 10 rezultate contin informatia cautata
Hash Value – valoare calculata cu un anumit algoritmData: 10667; Algoritm Hash: Data x 143; ValoareHash:1525381Daca stiu algoritmul si valoare Hash pot afla datele
Sisteme de criptaresimetrice – aceeasi cheie utilizata si la criptare si la decriptareasimetrice▪ cheie publica
▪ destinatar – la criptare▪ expeditor – la verificarea semnaturii digitale
▪ cheie privata▪ destinatar – la decriptare▪ expeditor – la semnare digitala
Certification Authorities
OTP –One Time Pad – dovedit matematicsigur (nepractic)DES (56b) Data Encryption Standard – 3DESAES (128, 192, 256b) Advanced Encryption StandardBlowfishTwofish (128, 192, 256b) Arcfour
Forta bruta32 biti – 232 pasi ~109 – oricine40 biti – 240 pasi ~109 – 1 saptamana cu 1 calculator modern56 biti – Effort substantial▪ retea de calculatoare in comun – cateva luni▪ hardware specializat (scump) – usor: accesibil pentru▪ guverne▪ org. criminale▪ companii mari
Forta bruta64 biti – Pot fi sparte▪ acum – guvernele mari▪ in cativa ani de: ▪ guverne mici▪ org. criminale▪ companii mari
80 biti – siguranta pentru cativa ani128 biti – siguranta pe viitor (109 pasi/s – mai multdecat varsta universului)
DSS – Digital Signature StandardRSA – Rivest, Shamir, AdlemanForta bruta256 biti – usor de spart512 biti – retea de calculatoare in cateva luni768 biti – momentan sigure dar nu pe termen lung1024 biti – sigure pentru cativa ani2048 – sigure pentru viitor
Laboratorul de microunde si optoelectronicahttp://rf‐[email protected]