NAME

       RC4_set_key, RC4 - RC4 encryption

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);

DESCRIPTION

       This library implements the Alleged RC4 cipher, which is described for example in 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 RC4_KEY key using the len bytes long key at data.

       RC4() encrypts or decrypts the len bytes of data at indata using key and places the result
       at outdata.  Repeated RC4() calls with the same 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.

       Applications should use the higher level functions EVP_EncryptInit(3) etc. instead of
       calling the RC4 functions directly.

RETURN VALUES

       RC4_set_key() and RC4() do not return values.

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.

SEE ALSO

       blowfish(3), des(3), rc2(3)

HISTORY

       RC4_set_key() and RC4() are available in all versions of SSLeay and OpenSSL.