Smart Phone and Next Generation Mobile Computing

344 Smart Phone and Next-Generation Mobile Computing

transmission where the cleartext is a stream of bits rather than a static

data block.

RC4 is the most widely used stream cipher, although it has been

shown that RC4 is not always secure. RC4 was designed by Ron Rivest

of RSA Security in 1987. RC4 (Rivest Cipher 4) is one of the four

ciphers that Rivest developed. In RC4, a variable-length key is first

used to perform a permutation of one byte according to a key schedul-

ing algorithm. The result, along with two index pointers, is fed

into a pseudo-random generation algorithm (PRGA) to produce the

keystream, which will be XORed with the cleartext to obtain the

cipher. RC4 has been found to have serious vulnerability in the

key scheduling algorithm that ...