1=pod
2
3=head1 NAME
4
5RC4_set_key, RC4 - RC4 encryption
6
7=head1 SYNOPSIS
8
9 #include <openssl/rc4.h>
10
11 void RC4_set_key(RC4_KEY *key, int len, const unsigned char *data);
12
13 void RC4(RC4_KEY *key, unsigned long len, const unsigned char *indata,
14          unsigned char *outdata);
15
16=head1 DESCRIPTION
17
18This library implements the Alleged RC4 cipher, which is described for
19example in I<Applied Cryptography>.  It is believed to be compatible
20with RC4[TM], a proprietary cipher of RSA Security Inc.
21
22RC4 is a stream cipher with variable key length.  Typically, 128 bit
23(16 byte) keys are used for strong encryption, but shorter insecure
24key sizes have been widely used due to export restrictions.
25
26RC4 consists of a key setup phase and the actual encryption or
27decryption phase.
28
29RC4_set_key() sets up the B<RC4_KEY> B<key> using the B<len> bytes long
30key at B<data>.
31
32RC4() encrypts or decrypts the B<len> bytes of data at B<indata> using
33B<key> and places the result at B<outdata>.  Repeated RC4() calls with
34the same B<key> yield a continuous key stream.
35
36Since RC4 is a stream cipher (the input is XORed with a pseudo-random
37key stream to produce the output), decryption uses the same function
38calls as encryption.
39
40Applications should use the higher level functions
41L<EVP_EncryptInit(3)|EVP_EncryptInit(3)>
42etc. instead of calling the RC4 functions directly.
43
44=head1 RETURN VALUES
45
46RC4_set_key() and RC4() do not return values.
47
48=head1 NOTE
49
50Certain conditions have to be observed to securely use stream ciphers.
51It is not permissible to perform multiple encryptions using the same
52key stream.
53
54=head1 SEE ALSO
55
56L<blowfish(3)|blowfish(3)>, L<des(3)|des(3)>, L<rc2(3)|rc2(3)>
57
58=head1 HISTORY
59
60RC4_set_key() and RC4() are available in all versions of SSLeay and OpenSSL.
61
62=cut
63