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.

An encryption cipher designed RSA Data Security. It allows key lengths up to 1024 bits and is a component in many encryption schemes, including SSL, WEP, and TKIP. (See SSL, WEP, TKIP). close

Stream cipher algorithm. A proprietary encryption algorithm available under license from RSA Data Security Inc.

A stream cipher that uses a key of any length between 1 and 2048 bits inclusive to encrypt or decrypt a block of text of arbitrary length.

The CryptoAPI algorithm name for the RC4 algorithm. See also RC4 stream algorithm.

RSA algorithm that uses a key and an initialization vector (IV) to create a key stream for encryption. RC4 is an underlying method within SSL.

An encryption algorithm designed at RSA Laboratories; specifically, a stream cipher of pseudo-random bytes that is used in WEP encryption.

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.

symmetric key stream cipher, developed by RSA Data Security Inc, and now widely available.

A symmetric stream cipher.

A stream cipher licensed by RSA Data Security [RSADSI]. A compatible cipher is described in [RC4].

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.

A streaming cipher technique; a stream cipher adds the output of a pseudorandom number generator bit by bit to the sequential bits of the digitized plain text.

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.