cryptography A cipher designed by RSA Data Security,Inc. which can accept keys of arbitrary length, and is

essentially a pseudo random number generator with the output

of the generator being XORed with the data stream to produce

the encrypted data. For this reason, it is very important

that the same RC4 key never be used to encrypt two different

data streams. The encryption mechanism used to be a trade

secret, until someone posted source code for an algorithm

onto Usenet News, claiming it to be equivalent to RC4. The

algorithm is very fast, its security is unknown, but breaking

it does not seem trivial either. There is very strong

evidence that the posted algorithm is indeed equivalent to

RC4.