细说 WiFi

因为日前正为了家里的 Mint 9 连接 AP with WPA2 encryption 而找些资料, 顺便来说说 WiFi.

 

WiFi 即 802.11 标准, 全名为 Wireless Fidelity (无线保真), 连接的方式有 ad hoc (自由直接), BS (Base Station),

AP (Access Point).

 

目前较为人知的标准:

 

802.11a : 5   GHz, 54 Mbits/s

802.11b : 2.4 GHz, 11 Mbits/s 

802.11g : 2.4 GHz, 54 MBits/s

802.11i : WPA/WPA2 Authentication

802.11n : 多重输入输出 (MIMO)

 

WPA (WiFi Protected Access) 是为了改善 WEP 缺点发展出来的. WEP 的全名为 Wired Equivalent Privacy

有线等效加密 or Wireless Encryption Protocol 无线加密协议.

 

企业版由 8021x server deliver key to client; 个人版设定一组 key, 称为 PSK (Pre-Share-Key)

 

WPA 的资料是以 128 bit key and 48 bit 初向量 (IV) 的 RC4 来加密, WPA 超越 WEP 的主要改进就是

使用中可以动态改变钥匙 Temporal key Integrity Protocol (TKIP), 而 WPA 的资料完整性则由 Michael

algorithm 的讯息认证码取代 WEP 的 CRC (循环冗余校验).

 

WPA2 是经由 WiFi Alliance 验证过的 IEEE802.11i 标准的认证形式, 在资料完整性由公认彻底安全的 CCMP 取代

Michael Algorithm, 有加密方式也由 AES 取代 RC4.

 

== WPA / WPA2 with CCMP in Mint 9 ==

 

To make sure that:

 

1. The package wpasupplicant is installed.

 

2. The ethernet cable is unplugged.

 

3. No firewall configuration is running.

 

To edit /etc/network/interfaces

 

1>> WPA configure file

 

auto lo iface lo inet loopback auto wlan0 iface wlan0 inet dhcp wpa-driver wext wpa-ssid <your-essid> wpa-ap-scan 1 wpa-proto WPA wpa-pairwise TKIP wpa-group TKIP wpa-key-mgmt WPA-PSK wpa-psk <your-hex-key>

2>> WPA2 configure file

auto lo iface lo inet loopback auto wlan0 iface wlan0 inet dhcp wpa-driver wext wpa-ssid <your-essid> wpa-ap-scan 1 wpa-proto RSN wpa-pairwise CCMP wpa-group CCMP wpa-key-mgmt WPA-PSK wpa-psk <your-hex-key>

 

 

 

<your-hex-key> can be generated by the command "wpa_passphrase <essid> <psk>".

 

To fetch the field next to "psk=" and paste it in the place of <your-hex-key>, then it should be worked after reboot.