/* rc4.h — ARC4 stream cipher for MSE/PE (BitTorrent message-stream encryption).
 *
 * MSE keys RC4 from a SHA-1 of the negotiated DH secret and *discards the first
 * 1024 keystream bytes* before use (the well-known RC4 keystream-bias defense),
 * so naut_rc4_init takes a drop count. This is obfuscation, not strong crypto —
 * its job is firewall/ISP evasion, and the engineering concern here is that it
 * costs real CPU at 10 GbE (see the throughput budget), hence it lives behind a
 * tight, in-place API.
 */
#ifndef NAUT_RC4_H
#define NAUT_RC4_H

#include "naut/common.h"

typedef struct { uint8_t s[256]; uint8_t i, j; } naut_rc4;

void naut_rc4_init(naut_rc4 *c, const void *key, size_t keylen, size_t drop);
/* XOR keystream into buf in place (encrypt == decrypt). */
void naut_rc4_xor(naut_rc4 *c, void *buf, size_t len);

#endif /* NAUT_RC4_H */