A royalty-based, RSA encryption algorithm (originally developed by a company called Rivest) that is widely used with SSL for Web-to-host security. For example, it’s one of the encryption algorithms supported by Host Access Client Package.
RC4 is a secret-key cryptosystem designed by Ron Rivest of RSA Data Security. It is a variable key-size operation that runs very quickly in software. While the algorithm is confidential and proprietary to RSA Data Security, Inc., it has been scrutinized under nondisclosure conditions by independent analysts, and it is considered secure.
A widely used stream cipher that is relatively fast, but with some significant problems. One practical problem is that it has a weak key setup algorithm, though this problem can be mitigated with care. Another more theoretical problem is that RC4's output is easy to distinguish from a truly random stream of numbers. This problem indicates that RC4 is probably not a good long-term choice for data security.
A variable length, secret key stream cipher. RC4 is intended as an alternate to DES and is approximately ten times as fast as DES. The exportable, 40-bit length version, used in Netscape SSL, has been broken by at least two separate organizations.
One of many symmetric key algorithms. Once a proprietary algorithm of RSA Data Security, Inc., RC4 creates keys of variable size which are called streaming ciphers; that is, they are used to encrypt a stream of data byte-by-byte as it goes by.
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 algorithm is very fast, its security is unknown, but breaking it does not seem trivial either.