Further Information
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Appendix A. Further Information

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Notes on the MAC address display in Ad-hoc mode
Security considerations on WEP cryptography

This appendix contains some extra information of items concerning wireless LAN that are not directly related to KWiFiManager.

Notes on the MAC address display in Ad-hoc mode

At first glance, the MAC address in the field Access Point seems to be wrong in Ad-hoc mode because it changes the first two bytes of the MAC address to 02. But actually, this is a hardcoded feature in wireless LAN cards.

Usually a card is connected to a “real”" access point. Then the correct MAC address is shown. If you change to Ad-hoc (or “Peer-to-peer”) mode, one of the computers must act as a server for the other computers. The first computer that enters a network, will set itself as server. So, all other computers connecting to the same Ad-hoc network will see that first computer as network server. But since this computer is not a “real” server (that is, it is not a permanently available access point), clients should be aware that the network they are connecting to is not a permanent one. IEEE standards for MAC addresses have a place reserved for such occasions: MAC addresses that are not globally valid have “02” as the first two bytes (these addresses are called “locally administered” addresses).

You can compare this to the non-global IP addresses like “192.168.*.*.

So, the implementors of wireless networking agreed to give these “virtual” network servers a MAC address that is within the “locally administered” scope. To keep this virtual MAC address unique, they used a little trick: they only changed the first two bytes of the MAC address of the wireless LAN card, and since the remaining ten bytes are still unique in the world, they have a unique address to use as network server.

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