The key-scheduling algorithm (KSA)
The key-scheduling algorithm is used to initialize the permutation in the array "S". "keylength" is defined as the number of bytes in the key and can be in the range 1 ≤ keylength ≤ 256, typically between 5 and 16, corresponding to a key length of 40 – 128 bits. First, the array "S" is initialized to the identity permutation. S is then processed for 256 iterations in a similar way to the main PRGA, but also mixes in bytes of the key at the same time.
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Wired Equivalent Privacy (WEP) is a
deprecated algorithm to secure
IEEE 802.11 wireless
networks. Wireless networks broadcast messages using
radio and are thus more susceptible to
eavesdropping than wired networks. When introduced in 1997,
[1] WEP was intended to provide
confidentiality comparable to that of a traditional wired
network.
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DSL (Digital Subscriber Line) 數位用戶線路:提供速率取決於與機房的距離---越近越好。
ADSL (Asynchronous DSL) 非對稱式DSL:可同時傳送資料和語音信號。
HDSL (High-bit-rate DSL) 高位元速率DSL
RADSL (Rate Adaptive DSL) 速率調適型DSL
SDSL (Synchronous DSL) 對稱式DSL:因會占用整個頻率範圍,就只能傳送資料。
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DTE and DCEThe terms DTE and DCE are very common in the datacommunications market. DTE is short for Data Terminal Equipment and DCE stands for Data Communications Equipment. But what do they really mean? As the full DTE name indicates this is a piece of device that ends a communication line, whereas the DCE provides a path for communication.
Let's say we have a computer on which wants to communicate with the Internet through a modem and a dial-up connection. To get to the Internet you tell your modem to dial the number of your provider. After your modems has dialed the number, the modem of the provider will answer your call and your will hear a lot of noise. Then it becomes quiet and you see your login prompt or your dialing program tells you the connection is established.
Now you have a connection with the server from your provider and you can wander the Internet.
In this example you PC is a Data Terminal (DTE). The two modems (yours and that one of your provider) are DCEs, they make the communication between you and your provider possible. But now we have to look at the server of your provider. Is that a DTE or DCE?
The answer is a DTE. It ends the communication line between you and the server. Although it gives you the possibility to surf around the glode. The reason why it is a DTE is that when you want to go from your provides server to another place it uses another interface. So DTE and DCE are interface dependend. It is e.g. possible that for your connection to the server, the server is a DTE, but that that same server is a DCE for the equipment that it is attached to on the rest of the Net.
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