#include "crypto_core_hsalsa20.h"
#include "crypto_scalarmult_curve25519.h"
#include "crypto_box.h"

static const unsigned char sigma[16] = "expand 32-byte k";
static const unsigned char n[16] = {0};

int crypto_box_beforenm(
  unsigned char *k,
  const unsigned char *pk,
  const unsigned char *sk
)
{
  unsigned char s[32];
  crypto_scalarmult_curve25519(s,sk,pk);
  return crypto_core_hsalsa20(k,n,s,sigma);
}