Document RC4.

crypto/rc4/rc4.h

@@ -77,8 +77,8 @@ typedef struct rc4_key_st
 
  
 const char *RC4_options(void);
-void RC4_set_key(RC4_KEY *key, int len, unsigned char *data);
+void RC4_set_key(RC4_KEY *key, int len, const unsigned char *data);
-void RC4(RC4_KEY *key, unsigned long len, unsigned char *indata,
+void RC4(RC4_KEY *key, unsigned long len, const unsigned char *indata,
 		unsigned char *outdata);
 
 #ifdef  __cplusplus

crypto/rc4/rc4_enc.c

@@ -67,7 +67,7 @@
  * Date: Wed, 14 Sep 1994 06:35:31 GMT
  */
 
-void RC4(RC4_KEY *key, unsigned long len, unsigned char *indata,
+void RC4(RC4_KEY *key, unsigned long len, const unsigned char *indata,
 	     unsigned char *outdata)
 	{
         register RC4_INT *d;

crypto/rc4/rc4_skey.c

@@ -85,7 +85,7 @@ const char *RC4_options(void)
  * Date: Wed, 14 Sep 1994 06:35:31 GMT
  */
 
-void RC4_set_key(RC4_KEY *key, int len, register unsigned char *data)
+void RC4_set_key(RC4_KEY *key, int len, const unsigned char *data)
 	{
         register RC4_INT tmp;
         register int id1,id2;

doc/crypto/rc4.pod

@@ -0,0 +1,58 @@
+=pod
+
+=head1 NAME
+
+RC4_set_key, RC4 - RC4 encryption
+
+=head1 SYNOPSIS
+
+ #include <openssl/rc4.h>
+
+ void RC4_set_key(RC4_KEY *key, int len, const unsigned char *data);
+
+ void RC4(RC4_KEY *key, unsigned long len, const unsigned char *indata,
+          unsigned char *outdata);
+
+=head1 DESCRIPTION
+
+This library implements the Alleged RC4 cipher, which is described for
+example in I<Applied Cryptography>.  It is believed to be compatible
+with RC4[TM], a proprietary cipher of RSA Security Inc.
+
+RC4 is a stream cipher with variable key length.  Typically, 128 bit
+(16 byte) keys are used for strong encryption, but shorter insecure
+key sizes have been widely used due to export restrictions.
+
+RC4 consists of a key setup phase and the actual encryption or
+decryption phase.
+
+RC4_set_key() sets up the B<RC4_KEY> B<key> using the B<len> bytes long
+key at B<data>.
+
+RC4() encrypts or decrypts the B<len> bytes of data at B<indata> using
+B<key> and places the result at B<outdata>.  Repeated RC4() calls with
+the same B<key> yield a continuous key stream.
+
+Since RC4 is a stream cipher (the input is XORed with a pseudo-random
+key stream to produce the output), decryption uses the same function
+calls as encryption.
+
+=head1 RETURN VALUES
+
+RC4_set_key() and RC4() do not return values.
+
+=head1 NOTE
+
+Certain conditions have to be observed to securely use stream ciphers.
+It is not permissible to perform multiple encryptions using the same
+key stream.
+
+=head1 SEE ALSO
+
+L<blowfish(3)|blowfish(3)>, L<des(3)|des(3)>, L<rc2(3)|rc2(3)>
+
+=head1 HISTORY
+
+RC4_set_key() and RC4() are available in all versions of SSLeay and OpenSSL.
+
+=cut