CRYPTOGRAPHY AND NETWORK SECURITY BY STALLINGS , 6 EDITION, QUESTION 3.

For WEP, data integrity and data confidentiality are achieved using the RC4 stream encryption algorithm . The transmitter of an MPDU performs the following steps, referred to as encapsulation:

1. The transmitter selects an initial vector (IV) value.

2. The IV value is concatenated with the WEP key shared by transmitter and receiver to form seed, or key input, to RC4.is ca

3. A 32 bit cyclic redundancy check is computed over all the bits of the MAC data field. The CRC is the common error detection code used in datalink control protocols. In this case, the CRC serves as a integrity check value (ICV).

4. The result of step 3 is encrypted using RC4 to form the cipher text block.

5. The plain text IV is prepended to the cipher text block to form the encapsulated MPDU for transmission.

(a) Draw a block diagram that illustrates the encapsulation process.

(b) Describe the steps at the receiver end to recover the plain text and perform the integrity check.

(c) Draw a block diagram that illustrates the part b.