RC4_set_key, RC4 - RC4 encryption
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);
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.
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.
Certain conditions have to be observed to securely use stream ciphers. It is not permissible to perform multiple encryptions using the same key stream.