RC4 is a stream cipher that has been widely used for inline encryption on the Internet with standards such as HTTP and SSH, or for WLANS with WEP or WPA.
The algorithm was developed in 1987 by Ronals L. Rivest and is officially secret. In 1994, ARC4 source code was published anonymously as open source.
The core of the method is the so-called S-box, which generates a random sequence that is linked bit by bit to the data stream and encrypts or decrypts it.
The first practical attack succeeded in 2001, and the attack methods were successively improved.
In February 2015, the Internet Engineering Task Force officially banned its use in RFC 7465 due to security deficiencies.