Encryption details Of WEP

Encryption details

WEP was included as the privacy component of the original IEEE 802.11 standard ratified in September 1999. WEP uses the stream cipher RC4 for confidentiality, and the CRC-32 checksum for integrity.It was deprecated in 2004 and is documented in the current standard.^[7]

Basic WEP encryption: RC4 keystream XORed with plaintext

Standard 64-bit WEP uses a 40 bit key (also known as WEP-40), which is concatenated with a 24-bit initialization vector (IV) to form the RC4 key. At the time that the original WEP standard was drafted, the U.S. Government's export restrictions on cryptographic technologylimited the key size. Once the restrictions were lifted, manufacturers of access points implemented an extended 128-bit WEP protocol using a 104-bit key size (WEP-104).

A 64-bit WEP key is usually entered as a string of 10 hexadecimal (base 16) characters (0-9 and A-F). Each character represents four bits, 10 digits of four bits each gives 40 bits; adding the 24-bit IV produces the complete 64-bit WEP key. Most devices also allow the user to enter the key as five ASCII characters, each of which is turned into eight bits using the character's byte value in ASCII; however, this restricts each byte to be a printable ASCII character, which is only a small fraction of possible byte values, greatly reducing the space of possible keys.

A 128-bit WEP key is usually entered as a string of 26 hexadecimal characters. 26 digits of four bits each gives 104 bits; adding the 24-bit IV produces the complete 128-bit WEP key. Most devices also allow the user to enter it as 13 ASCII characters.

A 256-bit WEP system is available from some vendors. As with the other WEP-variants 24 bits of that is for the IV, leaving 232 bits for actual protection. These 232 bits are typically entered as 58 hexadecimal characters. ((58 × 4 bits =) 232 bits) + 24 IV bits = 256-bit WEP key.

Key size is one of the security limitations in WEP. Cracking a longer key requires interception of more packets, but there are active attacks that stimulate the necessary traffic. There are other weaknesses in WEP, including the possibility of IV collisions and altered packets, that are not helped by using a longer key.