RC4 generates a pseudorandom stream of bits (a keystream). Example: Let A be the plain text and B be the keystream (A xor B) xor B = A . I cover a number of attacks on RC4, some of which are e ective against implementations of RC4 used in the real world. translated into its 40 character binary equivalent (for example, the ASCII key "pwd12" is equivalent to 0111000001110111011001000011000100110010 in binary). RC4 stream ciphers are strong in coding and easy to implement. to encrypt their email; it is an example of a practical hybrid encryption system which uses both secret key and public key . 01010000 = 11001000 RC4 … RC4 stream ciphers are simple to use. 4. I discuss a number of attack models for this class of ciphers, using attacks on RC4 as examples. Key-Scheduling Algorithm: Initialization: The entries of S are set equal to the values from 0 to 255 in ascending order, a temporary vector T, is ... Pseudo random generation algorithm (Stream Generation): Once the vector S is initialized, the input key will not be used. ciphers, using as an example the cipher RC4. As with any stream cipher, these can be used for encryption by combining it with the plaintext using bit-wise exclusive-or; decryption is performed the same way (since exclusive-or with given data is an involution). Example: RC4 Encryption 10011000 ? Advantages. The speed of operation in RC4 is fast as compared to other ciphers. RC4 ALGORITHM RC4 is a stream cipher, symmetric key algorithm. This is similar to the one-time pad except that generated pseudorandom bits, rather than a prepared stream, are used. The same algorithm is used for both encryption and decryption as the data stream is simply XORed with the generated key sequence. The next part of RC4 is the key-scheduling algorithm (KSA), listed below (from Wikipedia). This algorithm encrypts one byte at a time (or larger units on a time). RC4 stream ciphers do not require more memory. A key input is pseudorandom bit generator that produces a stream 8-bit number that is unpredictable without knowledge of input key, The output of the generator is called key-stream, is combined one byte at a time with the plaintext stream cipher using X-OR operation. for i from 0 to 255 S[i] := i endfor j := 0 for i from 0 to 255 j := (j + S[i] + key[i mod keylength]) mod 256