When creating a template on WCS with static WEP key with 128 bit encryption, and copying the existing key from IOS AP to WCS template, the user sees the a error message
"For Static ASCII WEP Key of size 128 bits, the key has to be exactly 16 ascii Characters long, whereas character entered are 28"
The key lengths shown on the WLCs are actually the number of bits that are in the shared secret and do not include the 24-bits of the Initialization Vector (IV). Many products, which includes the Aironet products, call it a 128-bit WEP key. In reality it is a 104-bit key with 24-bit IV. The key size of 104-bit is what you must enable on the WLC for 128-bit WEP encryption.
If you choose the 128-bit key size on the WLC, it is actually a 152-bit (128 + 24 IV) WEP key encryption. Only Cisco 1000 Series LAPs (AP1010, AP1020, AP1030) support the use of the WLC 128 bit WEP key setting.