WEP Encryption

based on the weak RC4 algorithm (symmetric key stream cipher)

IV (initialization vector) is a 24-bit value that augments a 40-bit WEP key to 64 bits and 104-bit WEP key to 128 bits and is sent in the clear (i.e. the effective key strength is only 40bits and 104bits)

IV + WEP key produce the key stream - ciphertext = plaintext XOR keystream, plaintext = ciphertext XOR keystream

the knowledge of the ciphertext and plaintext is enough to computate the key stream