Chapter Seventeen

Chapter Seventeen Network Security CIS 325: Data Communications

The Need for Security • Increased reliance on data communications results in greater vulnerability of data and systems • Losses associated with computerized fraud and thefts are much larger than non-computerized fraud and theft • Average bank robbery loss: $3000 • Average computer fraud loss: $300,000 CIS 325: Data Communications

Types of Security Threats • Disruption, Destruction, & Disaster • Viruses • Hardware, software, operator errors • Fires/floods/earthquakes • Unauthorized Access • Hackers • Disgruntled employees CIS 325: Data Communications

Passive Attacks • Primarily listening to traffic • Auth. Users can eavesdrop on line • Tap into patch panels • Intercept microwave transmissions • Tap lines to phone co. • Capture electromagnetic emissions • Fiber optic prevents most opportunities CIS 325: Data Communications

Active Attacks • Read stored data • Modify data in storage or during transmission • Disrupt service • Computer Emergency Response Team (CERT) • An expensive problem CIS 325: Data Communications

Conventional Encryption • 5 ingredients • plain text • encryption algorithm • secret key • ciphertext • decryption algorithm • Needs strong encryption algorithm • Sender and receiver must have same key CIS 325: Data Communications

Conventional Encryption • How to attack or de-cipher • cryptanalysis • brute force • Data Encryption Standard (DES) • Symmetric (same key to encrypt and decrypt) • Uses 64-bit key (100 quadrillion possibilities) CIS 325: Data Communications

Public Key Encryption • 6 ingredients • plain text • encryption algorithm • public key • private key • ciphertext • decryption algorithm CIS 325: Data Communications

Public Key Encryption • Process works regardless of order that keys are used • Many know your public key • Only you know private key • Keys and algorithm designed so they can’t be figured out even with one key known CIS 325: Data Communications

Public Key Process • You encode msg using rcvrs PUBLIC key • Only rcvr can decode and read with private key • No one else can read msg • Anyone with public key can send msg to that rcvr CIS 325: Data Communications

Public Key Process • Also can be used for authentication of sender • sender send msg using private key • rcvr decodes using public key • since only sender knows private key, that authenticates the sender • however, anyone with public key can read msg, so no good for secrecy CIS 325: Data Communications

Encryption Management • Link Encryption • devices to protect path from node to node • all traffic on path is secure • traffic most be decoded at each node for switching • traffic is vulnerable at switch CIS 325: Data Communications

Encryption Management • End-to-end Encryption • devices at each work station • traffic secure on path AND switches • But, switch needs to read control bits, so only data encrypted • Solution is to use combination of both CIS 325: Data Communications

Key Distribution • How to get keys to all parties • A physically delivers key to B • 3rd party delivers to A and B • A transmits key online to B • 3rd party transmits to A and B • Key Distribution Center • Session key for a single session CIS 325: Data Communications

Digital Signatures • Conventional Key doesn’t support non-repudiation • Authentication does, but very slow for big messages • Digital Signature relies on public-key and ‘secure hash function’ CIS 325: Data Communications

Digital Signatures • Hash Code created by doing some function on plain text • like a very fancy frame check sequence • Use private key to encrypt hash code only • Prevents anyone from modifying message • Provides authentication of sender CIS 325: Data Communications

Web Security • Problems • Alteration of web page • Access to server op sys • Eavesdropping • Impersonation • Solutions • Secure web site server • Secure site access CIS 325: Data Communications

Chapter Seventeen