1.\" $OpenBSD: RC4.3,v 1.8 2020/03/29 17:05:02 schwarze Exp $ 2.\" OpenSSL 99d63d46 Oct 26 13:56:48 2016 -0400 3.\" 4.\" This file was written by Ulf Moeller <ulf@openssl.org>. 5.\" Copyright (c) 2000 The OpenSSL Project. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in 16.\" the documentation and/or other materials provided with the 17.\" distribution. 18.\" 19.\" 3. All advertising materials mentioning features or use of this 20.\" software must display the following acknowledgment: 21.\" "This product includes software developed by the OpenSSL Project 22.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" 23.\" 24.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 25.\" endorse or promote products derived from this software without 26.\" prior written permission. For written permission, please contact 27.\" openssl-core@openssl.org. 28.\" 29.\" 5. Products derived from this software may not be called "OpenSSL" 30.\" nor may "OpenSSL" appear in their names without prior written 31.\" permission of the OpenSSL Project. 32.\" 33.\" 6. Redistributions of any form whatsoever must retain the following 34.\" acknowledgment: 35.\" "This product includes software developed by the OpenSSL Project 36.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" 37.\" 38.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 39.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 40.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 41.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 42.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 43.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 44.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 45.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 46.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 47.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 48.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 49.\" OF THE POSSIBILITY OF SUCH DAMAGE. 50.\" 51.Dd $Mdocdate: March 29 2020 $ 52.Dt RC4 3 53.Os 54.Sh NAME 55.Nm RC4_set_key , 56.Nm RC4 57.Nd RC4 encryption 58.Sh SYNOPSIS 59.In openssl/rc4.h 60.Ft void 61.Fo RC4_set_key 62.Fa "RC4_KEY *key" 63.Fa "int len" 64.Fa "const unsigned char *data" 65.Fc 66.Ft void 67.Fo RC4 68.Fa "RC4_KEY *key" 69.Fa "unsigned long len" 70.Fa "const unsigned char *indata" 71.Fa "unsigned char *outdata" 72.Fc 73.Sh DESCRIPTION 74This library implements the alleged RC4 cipher, which is described for 75example in 76.Qq Applied Cryptography . 77It is believed to be compatible with RC4[TM], a proprietary cipher of 78RSA Security Inc. 79.Pp 80RC4 is a stream cipher with variable key length. 81Typically, 128-bit (16-byte) keys are used for strong encryption, but 82shorter insecure key sizes have been widely used due to export 83restrictions. 84.Pp 85RC4 consists of a key setup phase and the actual encryption or 86decryption phase. 87.Pp 88.Fn RC4_set_key 89sets up the 90.Vt RC4_KEY 91.Fa key 92using the 93.Fa len 94bytes long key at 95.Fa data . 96.Pp 97.Fn RC4 98encrypts or decrypts the 99.Fa len 100bytes of data at 101.Fa indata 102using 103.Fa key 104and places the result at 105.Fa outdata . 106Repeated 107.Fn RC4 108calls with the same 109.Fa key 110yield a continuous key stream. 111.Pp 112Since RC4 is a stream cipher (the input is XOR'ed with a pseudo-random 113key stream to produce the output), decryption uses the same function 114calls as encryption. 115.Sh SEE ALSO 116.Xr blowfish 3 , 117.Xr EVP_EncryptInit 3 , 118.Xr EVP_rc4 3 119.Sh HISTORY 120.Fn RC4_set_key 121and 122.Fn RC4 123appeared in SSLeay 0.4 or earlier and have been available since 124.Ox 2.4 . 125.Sh BUGS 126This cipher is broken and should no longer be used. 127