V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

RC4
       Rivest Cipher / Ron's Code 4 (cryptography)


The Free On-line Dictionary of Computing (30 December 2018):

RC4

    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.

   The United States government routinely approves RC4 with
   40-bit keys for export.  Keys this small can be easily broken
   by governments, criminals, and amateurs.  The exportable
   version of Netscape's Secure Socket Layer, which uses
   RC4-40, was broken by at least two independent groups.
   Breaking it took about eight days; in many universities or
   companies the same computing power is available to any
   computer science student.

   See also Damien Doligez's SSL cracking page
   (http://pauillac.inria.fr/~doligez/ssl/), RC4 Source and
   Information (http://cs.hut.fi/crypto/rc4), SSLeay
   (http://cs.hut.fi/crypto/software.html#ssleay), Crypto++
   (http://cs.hut.fi/crypto/software.html#crypto++), Ssh
   (http://cs.hut.fi/crypto/software.html#ssh), A
   collection of articles
   (http://cs.hut.fi/crypto/rc4-breaking).

   (1996-10-28)