Local Wireless Network - PowerPoint PPT Presentation

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Local Wireless Network

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  1. Local Wireless Network - An wireless Access Point (AP) which is the bridge the ethernet network and the wireless network -The AP protect its wireless network from unauthorized users with different security protocols. - One of the most basic and first security protocols is the WEP Shared Key Authentication

  2. WEP shared key authentication • -

  3. The WEP Shared Key Authentication protocoll process in 5 steps between the client and the access point on the wireless network. • -The client sends and authentication request to the access point. • -The access point sends and nonce text to the client. • -The client uses its preconfigured 128-bit shared key to encrypt the nonce text from the access point. • -The access point decrypts the encrypted nonce text by using its preconfigured WEP key that corresponds with the shared key. The access point then compares the decrypted text with the original nonce text being sent. If the two nonce texts matches eachother they share the same WEP key and the access point can authenticate the client • -The client can then connect to the network through the wireless access point

  4. Configuring WEP keys • - Some manufacturers support only one 128-bit key, but usually most access points can handle 4 different WEP keys. • - The 128-bit WEP Key is expressed as 13 sets of two hexadecimal digits (0-9 and A-F). For example, "12 34 56 78 90 AB CD EF 12 34 56 78 90" is a 128-bit WEP key.

  5. WEP weaknesses • - A high percentage of wireless networks have WEP disabled because of the high administrative workload of maintaining a shared WEP key • - WEP has the same problem as all systems based upon shared keys: any secret held by more than one person soon becomes public knowledge. When users leave the network the WEP key needs to be changed, which can be a frequent problem in big networks with many users comming and go. • - The WEP checksum is linear and predictable.


  6. All traffic from outside to inside, and vice versa, passes through the firewall • Only authorized traffic, as defined by the local security policy will be allowed to pass • The firewall itself is immune to penetration Firewall has three goals -

  7. Three different categories - Traditional Packet Filters - Stateful Packet Filters - Applications gateways

  8. Packet Filters Filtering decisions are typically based on: - IP source or destination address - Protocol type in IP datagram field: TCP, UDP, ICMP, OSPF, and so on- TCP or UDP source and destination port- TCP flag bits: SYN, ACK and so on- Different rules for the different router interfaces - Different rules for datagram leaving and entering the network

  9. Access control list for a router interface

  10. Access control list for stateful filters

  11. Application Gateway • - Finer-level security, firewall combine packet filtering with application gateways. • - Applications gateway looks beyond the IP/TCP/UDP header • Internal network often have multiple applications gateways, for example, gateways for Telnet, HTTP, FTP and email.

  12. Weaknesses in WEP security design Sharing a key with all users. Problem: Liable for security issues trough transmission in unprotected channels and malicious users. Solution: Public-key protocol for authenticating indivudal keys. Such as SSL (BankID, FTP-rings, etc.)

  13. Base stations are never authenticated Problem: 1337-h4xx0rz who knows the shared key can introduce a spoof an eavesdrop on the traffic. Solution: Base stations should supply a certificate Stream cipher repetition. Problem: Patterns can be found since the same key is always used. Solution: Negotiate a new key before a pattern reasonably could be found. Even with higher encryption problems were found so a range of decryption algroithms can be deployed.

  14. Low level of encryption was used in the first versions Problem: With lower levels of encryption brute force hacking is possible. Solution: Change to 128-bit keys only Users not deploying the full range of security measures. Problem: People simply didn’t adapt to the new security specifications. Solution: Better default settings and documentation