ed25519/sign.c

#include "ed25519.h"
#include "sha512.h"
#include "ge.h"
#include "sc.h"


int ed25519_sign(unsigned char *signature, const unsigned char *message, unsigned int message_len, const unsigned char *sign_key)
{
  unsigned char az[64];
  unsigned char r[64];
  unsigned char hram[64];
  ge_p3 R;
  sha512_ctx hash;

  sha512(sign_key, 32, az);
  az[0] &= 248;
  az[31] &= 63;
  az[31] |= 64;

  sha512_init(&hash);
  sha512_update(&hash, az + 32, 32);
  sha512_update(&hash, message, message_len);
  sha512_final(&hash, r);

  sc_reduce(r);
  ge_scalarmult_base(&R, r);
  ge_p3_tobytes(signature, &R);

  sha512_init(&hash);
  sha512_update(&hash, signature, 32);
  sha512_update(&hash, sign_key + 32, 32);
  sha512_update(&hash, message, message_len);
  sha512_final(&hash, hram);

  sc_reduce(hram);
  sc_muladd(signature + 32, hram, az, r);

  return 0;
}