src/eckey_impl.h

   1 /**********************************************************************
   2  * Copyright (c) 2013, 2014 Pieter Wuille                             *
   3  * Distributed under the MIT software license, see the accompanying   *
   4  * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
   5  **********************************************************************/
   6
   7 #ifndef SECP256K1_ECKEY_IMPL_H
   8 #define SECP256K1_ECKEY_IMPL_H
   9
  10 #include "eckey.h"
  11
  12 #include "scalar.h"
  13 #include "field.h"
  14 #include "group.h"
  15 #include "ecmult_gen.h"
  16
  17 static int secp256k1_eckey_pubkey_parse(secp256k1_ge *elem, const unsigned char *pub, size_t size) {
  18     if (size == 33 && (pub[0] == SECP256K1_TAG_PUBKEY_EVEN || pub[0] == SECP256K1_TAG_PUBKEY_ODD)) {
  19         secp256k1_fe x;
  20         return secp256k1_fe_set_b32(&x, pub+1) && secp256k1_ge_set_xo_var(elem, &x, pub[0] == SECP256K1_TAG_PUBKEY_ODD);
  21     } else if (size == 65 && (pub[0] == 0x04 || pub[0] == 0x06 || pub[0] == 0x07)) {
  22         secp256k1_fe x, y;
  23         if (!secp256k1_fe_set_b32(&x, pub+1) || !secp256k1_fe_set_b32(&y, pub+33)) {
  24             return 0;
  25         }
  26         secp256k1_ge_set_xy(elem, &x, &y);
  27         if ((pub[0] == SECP256K1_TAG_PUBKEY_HYBRID_EVEN || pub[0] == SECP256K1_TAG_PUBKEY_HYBRID_ODD) &&
  28             secp256k1_fe_is_odd(&y) != (pub[0] == SECP256K1_TAG_PUBKEY_HYBRID_ODD)) {
  29             return 0;
  30         }
  31         return secp256k1_ge_is_valid_var(elem);
  32     } else {
  33         return 0;
  34     }
  35 }
  36
  37 static int secp256k1_eckey_pubkey_serialize(secp256k1_ge *elem, unsigned char *pub, size_t *size, int compressed) {
  38     if (secp256k1_ge_is_infinity(elem)) {
  39         return 0;
  40     }
  41     secp256k1_fe_normalize_var(&elem->x);
  42     secp256k1_fe_normalize_var(&elem->y);
  43     secp256k1_fe_get_b32(&pub[1], &elem->x);
  44     if (compressed) {
  45         *size = 33;
  46         pub[0] = secp256k1_fe_is_odd(&elem->y) ? SECP256K1_TAG_PUBKEY_ODD : SECP256K1_TAG_PUBKEY_EVEN;
  47     } else {
  48         *size = 65;
  49         pub[0] = SECP256K1_TAG_PUBKEY_UNCOMPRESSED;
  50         secp256k1_fe_get_b32(&pub[33], &elem->y);
  51     }
  52     return 1;
  53 }
  54
  55 static int secp256k1_eckey_privkey_tweak_add(secp256k1_scalar *key, const secp256k1_scalar *tweak) {
  56     secp256k1_scalar_add(key, key, tweak);
  57     if (secp256k1_scalar_is_zero(key)) {
  58         return 0;
  59     }
  60     return 1;
  61 }
  62
  63 static int secp256k1_eckey_pubkey_tweak_add(const secp256k1_ecmult_context *ctx, secp256k1_ge *key, const secp256k1_scalar *tweak) {
  64     secp256k1_gej pt;
  65     secp256k1_scalar one;
  66     secp256k1_gej_set_ge(&pt, key);
  67     secp256k1_scalar_set_int(&one, 1);
  68     secp256k1_ecmult(ctx, &pt, &pt, &one, tweak);
  69
  70     if (secp256k1_gej_is_infinity(&pt)) {
  71         return 0;
  72     }
  73     secp256k1_ge_set_gej(key, &pt);
  74     return 1;
  75 }
  76
  77 static int secp256k1_eckey_privkey_tweak_mul(secp256k1_scalar *key, const secp256k1_scalar *tweak) {
  78     if (secp256k1_scalar_is_zero(tweak)) {
  79         return 0;
  80     }
  81
  82     secp256k1_scalar_mul(key, key, tweak);
  83     return 1;
  84 }
  85
  86 static int secp256k1_eckey_pubkey_tweak_mul(const secp256k1_ecmult_context *ctx, secp256k1_ge *key, const secp256k1_scalar *tweak) {
  87     secp256k1_scalar zero;
  88     secp256k1_gej pt;
  89     if (secp256k1_scalar_is_zero(tweak)) {
  90         return 0;
  91     }
  92
  93     secp256k1_scalar_set_int(&zero, 0);
  94     secp256k1_gej_set_ge(&pt, key);
  95     secp256k1_ecmult(ctx, &pt, &pt, tweak, &zero);
  96     secp256k1_ge_set_gej(key, &pt);
  97     return 1;
  98 }
  99
 100 #endif /* SECP256K1_ECKEY_IMPL_H */