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Private network

Firewall Implementation. Web clients. Gateway. R2. R1. Private. Screened. Packet. Packet. inner. subnet. subnet. filtering. filtering. router. router. Web server. Internet. (outside. Private network. firewall). Flow of network traffic. (inside firewall).

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Private network

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  1. Firewall Implementation Web clients Gateway R2 R1 Private Screened Packet Packet inner subnet subnet filtering filtering router router Web server Internet (outside Private network firewall) Flow of network traffic (inside firewall) A Web server on a screened subnet firewall

  2. Firewall Components Telnet Telnet application T Telnet server TS proxy TP Packet filtering Port Port router R P2 P3 Port P1 Port P4 Client inside Firewall Private network Internet ( inside firewall) ( outside firewall) Telnet proxy on a screened host firewall topology. Firewall Implementation

  3. Cryptography • A cryptographic algorithm or cipher is used to encrypt and decrypt messages. • Encrypted message is called ciphertext. • Cryptographic algorithms use one or more variables called keys. • Keys are very large numbers.

  4. Cryptographic Algorithms • Private key cryptography • one secret key • ensures confidentiality • Public key cryptography • a matched key pair (public & private) • used for authentication • Hashing Algorithms • convert message to a digest (unique number) • ensures integrity

  5. Digital Signatures • Combines public key cryptography and hashing algorithms. • message digest is encrypted using public key cryptography. • Can be enhanced using private (secret) cryptography to encrypt the message. • Document is signed & encrypted.

  6. ENCRYPT DECRYPT Encrypted (using private (using public message and key) key) signature Transmission

  7. INTRANETS • Internal private corporate networks. • Standalone or sit on the secure side of a firewall. • Leverage the public technology on which the Web is built. • Private version of the Internet.

  8. EXTRANET • Extends the corporate backbone to outsiders and other intranets. • Uses a VPN that creates secure channel across public networks. • VPN ties a corporation with its suppliers, employees, and business partners. • Automotive Network Exchange (ANX) - an IPSec-based VPN connecting auto makers with thousands of auto industry suppliers.

  9. HyperText Markup Language (HTML) • Web pages are written in HTML that specifies general guidelines for display. • Web browser translates the specification into commands for particular hardware. • HTML uses free-format input; HTML can contain arbitrary spaces and extra lines. • HTML instructions are separated from text to be displayed using ‘<‘ and ‘>’ symbols.

  10. Sections of a HTML Document • Two main parts - a heading and a body. • <HTML> • <HEAD> • <TITLE> • Actual Title • </TITLE> • Additional heading info; if needed • </HEAD> • <BODY> • ……. Text • </BODY> • </HTML>

  11. HTML Basics • Paragraph tags are used to determine how to group sentences in paragraphs. • <P> • Paragraph 1 • <P> • Paragraph 2 • <P> • Paragraph 3 • Line break tag <BR>

  12. HTML Basics • Items that correspond to a link are said to be anchored. A link begins with the tag <A>, and ends with the tag </A>. • <A HREF = “http://www.okstate.edu/cocim”> Center for CIM • </A> • Browser displays Center for CIM

  13. HTML Basics • Numbered (ordered) List • <OL><LI>Item 1<LI>Item 2<LI>Item 3</OL> • 1. Item 1 • 2. Item 2 • 3. Item 3 • Unnumbered (unordered or bulleted) List • <UL><LI>Item 1<LI>Item 2<LI>Item 3</UL> • Item 1 • Item 2 • Item 3

  14. HTML Basics • Inserting images - the IMG tag. • <IMG SRC=“xyz.gif”> • An image can appear by itself or adjacent to text. • Alignment • <IMG SRC=“xyz.gif” ALIGN = CENTER>

  15. HTML Basics • Making images correspond to a selectable link. • <A HREF=“http://www.okstate.edu/cocim/index.htm”> • <IMG SRC=“ccim.jpg”> • </A> • Specifying background color • <BODY BGCOLOR=“#000000” background=”xyz.gif"> • </BODY> • displays black background color and image in the background

  16. HTML Basics • Displaying tables • <TABLE COLS=2 ROWS=2> • <TR><TD>a</TD><TD>b</TD></TR> • <TR><TD>x</TD><TD>y</TD></TR> • </TABLE> • Specifying multiple links within a single image • <MAP><AREA SHAPE="RECT" COORDS="64, 56, 261, 95" HREF="http://www.okstate.edu”><AREA SHAPE="RECT" COORDS="108, 5, 219, 49" HREF="http://osu.okstate.edu/cocim"> • </MAP>

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