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what is cisco ccna data center.Since that challenge text is in plaintext, an attacker can easily use it to obtain the static WEP key used to create the encrypted packet.The attacker's method is simply to reconstruct the key using the challenge and response. WEP uses the RC4 encryption method.272 Chapter 17 Wireless Network Security AssuranceNote: It is important to note that although WEP keys can be used to encrypt challenge text, they can only be used for authentication. When associated with an AP, WEP cannot be used to hide, protect, or encrypt any user data.Some other things to note related to the use of WEP are the length of the key, there are 3 key lengths that can be used. 40-bit keys. 104-bit keys. 128-bit keys. It has to be stressed that these values are not the ones you want to consider. As you can see, the key combines the 24-bit Initialization Vector (IV,Initialization Vector) o IV is the block of bits used to generate the unique encryption key. When adding 24-bit IV to a 40-bit key, the resultant key length changes to 64 bits. When 24-bit IV is combined with a 104-bit key, the result is 128 bits. When combining a 24-bit IV with a '128-bit key, the result is 152 bits. This is always a headache for Windows users, because the maximum key supported for local users is 128 bits. If you choose a key length of 128 bits, combining it with IV will result in a 152-bit key, thus causing authentication failure. Therefore, a 104-bit key should be used under Windows, otherwise it does not work.After authentication, an associated identifier is issued to the client, and the client can then start sending data. From this point on, WEP is used to encrypt traffic. Figure 17-5 shows the static WEP configuration.Figure 17-5 Configuring WEP17.2 Basic Topics 2733. MAC Address Filtering