3. History
RC4 was designed by Ron Rivest of RSA Security in 1987. While it is officially
termed “Rivest Cipher 4”.
RC4 was initially a trade secret, but in September 1994 a description of it was
anonymously posted to the Cypherpunks mailing list.
and from there to many sites on the Internet. RC4 has become part of some
commonly used encryption protocols and standards, including WEP and WPA
for wireless cards.
The main factors in RC4's success over such a wide range of applications are
its speed and simplicity: efficient implementations in both software and
hardware are very easy to develop.
4. Analysis of RC4
Advantages
Faster than DES
Enormous key space (average of 1700 bits)
RC4 is used in popular protocols such as Secure Sockets Layer (SSL)
(to protect Internet traffic) SSL and
In 802.11 WEP(to secure wireless networks).
Disadvantages
Large number of “weak” keys 1 of 256
“Weak” keys can be detected and exploited with a high probability
5. Weaknesses of RC4
Almost all weaknesses are in the KSA since attacking the PRGA is fairly
infeasible due to the huge effective key. The fastest known method requires
2700 time.
The KSA can be attacked with several methods mainly because of the simple
initialization permutation used.
Invariance Weakness is the most devastating attack.
(5% chance of guessing one or more bytes of the key.)
6. RC4 Description
Symmetric
Stream Cipher
Two main parts:
KSA (Key Scheduling Algorithm)
PRGA (Pseudo Random Generation Algorithm)
Notation:
S = {0, 1, 2, … N-1} is the initial permutation
l = length of