src/eccryptoverify.cpp

   1 // Copyright (c) 2009-2010 Satoshi Nakamoto
   2 // Copyright (c) 2009-2014 The Bitcoin Core developers
   3 // Distributed under the MIT software license, see the accompanying
   4 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   5
   6 #include "eccryptoverify.h"
   7
   8 namespace {
   9
  10 int CompareBigEndian(const unsigned char *c1, size_t c1len, const unsigned char *c2, size_t c2len) {
  11     while (c1len > c2len) {
  12         if (*c1)
  13             return 1;
  14         c1++;
  15         c1len--;
  16     }
  17     while (c2len > c1len) {
  18         if (*c2)
  19             return -1;
  20         c2++;
  21         c2len--;
  22     }
  23     while (c1len > 0) {
  24         if (*c1 > *c2)
  25             return 1;
  26         if (*c2 > *c1)
  27             return -1;
  28         c1++;
  29         c2++;
  30         c1len--;
  31     }
  32     return 0;
  33 }
  34
  35 /** Order of secp256k1's generator minus 1. */
  36 const unsigned char vchMaxModOrder[32] = {
  37     0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
  38     0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFE,
  39     0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,
  40     0xBF,0xD2,0x5E,0x8C,0xD0,0x36,0x41,0x40
  41 };
  42
  43 /** Half of the order of secp256k1's generator minus 1. */
  44 const unsigned char vchMaxModHalfOrder[32] = {
  45     0x7F,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
  46     0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
  47     0x5D,0x57,0x6E,0x73,0x57,0xA4,0x50,0x1D,
  48     0xDF,0xE9,0x2F,0x46,0x68,0x1B,0x20,0xA0
  49 };
  50
  51 const unsigned char vchZero[1] = {0};
  52 } // anon namespace
  53
  54 namespace eccrypto {
  55
  56 bool Check(const unsigned char *vch) {
  57     return vch &&
  58            CompareBigEndian(vch, 32, vchZero, 0) > 0 &&
  59            CompareBigEndian(vch, 32, vchMaxModOrder, 32) <= 0;
  60 }
  61
  62 bool CheckSignatureElement(const unsigned char *vch, int len, bool half) {
  63     return vch &&
  64            CompareBigEndian(vch, len, vchZero, 0) > 0 &&
  65            CompareBigEndian(vch, len, half ? vchMaxModHalfOrder : vchMaxModOrder, 32) <= 0;
  66 }
  67
  68 } // namespace eccrypto