src/key.h

   1 // Copyright (c) 2009-2010 Satoshi Nakamoto
   2 // Copyright (c) 2009-2012 The Bitcoin developers
   3 // Distributed under the MIT/X11 software license, see the accompanying
   4 // file license.txt or http://www.opensource.org/licenses/mit-license.php.
   5 #ifndef BITCOIN_KEY_H
   6 #define BITCOIN_KEY_H
   7
   8 #include <stdexcept>
   9 #include <vector>
  10
  11 #include <openssl/ec.h>
  12 #include <openssl/ecdsa.h>
  13 #include <openssl/obj_mac.h>
  14
  15 #include "serialize.h"
  16 #include "uint256.h"
  17
  18 // secp160k1
  19 // const unsigned int PRIVATE_KEY_SIZE = 192;
  20 // const unsigned int PUBLIC_KEY_SIZE  = 41;
  21 // const unsigned int SIGNATURE_SIZE   = 48;
  22 //
  23 // secp192k1
  24 // const unsigned int PRIVATE_KEY_SIZE = 222;
  25 // const unsigned int PUBLIC_KEY_SIZE  = 49;
  26 // const unsigned int SIGNATURE_SIZE   = 57;
  27 //
  28 // secp224k1
  29 // const unsigned int PRIVATE_KEY_SIZE = 250;
  30 // const unsigned int PUBLIC_KEY_SIZE  = 57;
  31 // const unsigned int SIGNATURE_SIZE   = 66;
  32 //
  33 // secp256k1:
  34 // const unsigned int PRIVATE_KEY_SIZE = 279;
  35 // const unsigned int PUBLIC_KEY_SIZE  = 65;
  36 // const unsigned int SIGNATURE_SIZE   = 72;
  37 //
  38 // see www.keylength.com
  39 // script supports up to 75 for single byte push
  40
  41 int extern EC_KEY_regenerate_key(EC_KEY *eckey, BIGNUM *priv_key);
  42 int extern ECDSA_SIG_recover_key_GFp(EC_KEY *eckey, ECDSA_SIG *ecsig, const unsigned char *msg, int msglen, int recid, int check);
  43
  44 class key_error : public std::runtime_error
  45 {
  46 public:
  47     explicit key_error(const std::string& str) : std::runtime_error(str) {}
  48 };
  49
  50
  51 // secure_allocator is defined in serialize.h
  52 // CPrivKey is a serialized private key, with all parameters included (279 bytes)
  53 typedef std::vector<unsigned char, secure_allocator<unsigned char> > CPrivKey;
  54 // CSecret is a serialization of just the secret parameter (32 bytes)
  55 typedef std::vector<unsigned char, secure_allocator<unsigned char> > CSecret;
  56
  57 class CKey
  58 {
  59 protected:
  60     EC_KEY* pkey;
  61     bool fSet;
  62     bool fCompressedPubKey;
  63
  64     void SetCompressedPubKey()
  65     {
  66         EC_KEY_set_conv_form(pkey, POINT_CONVERSION_COMPRESSED);
  67         fCompressedPubKey = true;
  68     }
  69
  70 public:
  71
  72     void Reset()
  73     {
  74         fCompressedPubKey = false;
  75         pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
  76         if (pkey == NULL)
  77             throw key_error("CKey::CKey() : EC_KEY_new_by_curve_name failed");
  78         fSet = false;
  79     }
  80
  81     CKey()
  82     {
  83         Reset();
  84     }
  85
  86     CKey(const CKey& b)
  87     {
  88         pkey = EC_KEY_dup(b.pkey);
  89         if (pkey == NULL)
  90             throw key_error("CKey::CKey(const CKey&) : EC_KEY_dup failed");
  91         fSet = b.fSet;
  92     }
  93
  94     CKey& operator=(const CKey& b)
  95     {
  96         if (!EC_KEY_copy(pkey, b.pkey))
  97             throw key_error("CKey::operator=(const CKey&) : EC_KEY_copy failed");
  98         fSet = b.fSet;
  99         return (*this);
 100     }
 101
 102     ~CKey()
 103     {
 104         EC_KEY_free(pkey);
 105     }
 106
 107     bool IsNull() const
 108     {
 109         return !fSet;
 110     }
 111
 112     bool IsCompressed() const
 113     {
 114         return fCompressedPubKey;
 115     }
 116
 117     void MakeNewKey(bool fCompressed)
 118     {
 119         if (!EC_KEY_generate_key(pkey))
 120             throw key_error("CKey::MakeNewKey() : EC_KEY_generate_key failed");
 121         if (fCompressed)
 122             SetCompressedPubKey();
 123         fSet = true;
 124     }
 125
 126     bool SetPrivKey(const CPrivKey& vchPrivKey)
 127     {
 128         const unsigned char* pbegin = &vchPrivKey[0];
 129         if (!d2i_ECPrivateKey(&pkey, &pbegin, vchPrivKey.size()))
 130             return false;
 131         fSet = true;
 132         return true;
 133     }
 134
 135     bool SetSecret(const CSecret& vchSecret, bool fCompressed = false)
 136     {
 137         EC_KEY_free(pkey);
 138         pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
 139         if (pkey == NULL)
 140             throw key_error("CKey::SetSecret() : EC_KEY_new_by_curve_name failed");
 141         if (vchSecret.size() != 32)
 142             throw key_error("CKey::SetSecret() : secret must be 32 bytes");
 143         BIGNUM *bn = BN_bin2bn(&vchSecret[0],32,BN_new());
 144         if (bn == NULL)
 145             throw key_error("CKey::SetSecret() : BN_bin2bn failed");
 146         if (!EC_KEY_regenerate_key(pkey,bn))
 147         {
 148             BN_clear_free(bn);
 149             throw key_error("CKey::SetSecret() : EC_KEY_regenerate_key failed");
 150         }
 151         BN_clear_free(bn);
 152         fSet = true;
 153         if (fCompressed || fCompressedPubKey)
 154             SetCompressedPubKey();
 155         return true;
 156     }
 157
 158     CSecret GetSecret(bool &fCompressed) const
 159     {
 160         CSecret vchRet;
 161         vchRet.resize(32);
 162         const BIGNUM *bn = EC_KEY_get0_private_key(pkey);
 163         int nBytes = BN_num_bytes(bn);
 164         if (bn == NULL)
 165             throw key_error("CKey::GetSecret() : EC_KEY_get0_private_key failed");
 166         int n=BN_bn2bin(bn,&vchRet[32 - nBytes]);
 167         if (n != nBytes)
 168             throw key_error("CKey::GetSecret(): BN_bn2bin failed");
 169         fCompressed = fCompressedPubKey;
 170         return vchRet;
 171     }
 172
 173     CPrivKey GetPrivKey() const
 174     {
 175         unsigned int nSize = i2d_ECPrivateKey(pkey, NULL);
 176         if (!nSize)
 177             throw key_error("CKey::GetPrivKey() : i2d_ECPrivateKey failed");
 178         CPrivKey vchPrivKey(nSize, 0);
 179         unsigned char* pbegin = &vchPrivKey[0];
 180         if (i2d_ECPrivateKey(pkey, &pbegin) != nSize)
 181             throw key_error("CKey::GetPrivKey() : i2d_ECPrivateKey returned unexpected size");
 182         return vchPrivKey;
 183     }
 184
 185     bool SetPubKey(const std::vector<unsigned char>& vchPubKey)
 186     {
 187         const unsigned char* pbegin = &vchPubKey[0];
 188         if (!o2i_ECPublicKey(&pkey, &pbegin, vchPubKey.size()))
 189             return false;
 190         fSet = true;
 191         if (vchPubKey.size() == 33)
 192             SetCompressedPubKey();
 193         return true;
 194     }
 195
 196     std::vector<unsigned char> GetPubKey() const
 197     {
 198         unsigned int nSize = i2o_ECPublicKey(pkey, NULL);
 199         if (!nSize)
 200             throw key_error("CKey::GetPubKey() : i2o_ECPublicKey failed");
 201         std::vector<unsigned char> vchPubKey(nSize, 0);
 202         unsigned char* pbegin = &vchPubKey[0];
 203         if (i2o_ECPublicKey(pkey, &pbegin) != nSize)
 204             throw key_error("CKey::GetPubKey() : i2o_ECPublicKey returned unexpected size");
 205         return vchPubKey;
 206     }
 207
 208     bool Sign(uint256 hash, std::vector<unsigned char>& vchSig)
 209     {
 210         unsigned int nSize = ECDSA_size(pkey);
 211         vchSig.resize(nSize); // Make sure it is big enough
 212         if (!ECDSA_sign(0, (unsigned char*)&hash, sizeof(hash), &vchSig[0], &nSize, pkey))
 213         {
 214             vchSig.clear();
 215             return false;
 216         }
 217         vchSig.resize(nSize); // Shrink to fit actual size
 218         return true;
 219     }
 220
 221     // create a compact signature (65 bytes), which allows reconstructing the used public key
 222     // The format is one header byte, followed by two times 32 bytes for the serialized r and s values.
 223     // The header byte: 0x1B = first key with even y, 0x1C = first key with odd y,
 224     //                  0x1D = second key with even y, 0x1E = second key with odd y
 225     bool SignCompact(uint256 hash, std::vector<unsigned char>& vchSig)
 226     {
 227         bool fOk = false;
 228         ECDSA_SIG *sig = ECDSA_do_sign((unsigned char*)&hash, sizeof(hash), pkey);
 229         if (sig==NULL)
 230             return false;
 231         vchSig.clear();
 232         vchSig.resize(65,0);
 233         int nBitsR = BN_num_bits(sig->r);
 234         int nBitsS = BN_num_bits(sig->s);
 235         if (nBitsR <= 256 && nBitsS <= 256)
 236         {
 237             int nRecId = -1;
 238             for (int i=0; i<4; i++)
 239             {
 240                 CKey keyRec;
 241                 keyRec.fSet = true;
 242                 if (fCompressedPubKey)
 243                     keyRec.SetCompressedPubKey();
 244                 if (ECDSA_SIG_recover_key_GFp(keyRec.pkey, sig, (unsigned char*)&hash, sizeof(hash), i, 1) == 1)
 245                     if (keyRec.GetPubKey() == this->GetPubKey())
 246                     {
 247                         nRecId = i;
 248                         break;
 249                     }
 250             }
 251
 252             if (nRecId == -1)
 253                 throw key_error("CKey::SignCompact() : unable to construct recoverable key");
 254
 255             vchSig[0] = nRecId+27+(fCompressedPubKey ? 4 : 0);
 256             BN_bn2bin(sig->r,&vchSig[33-(nBitsR+7)/8]);
 257             BN_bn2bin(sig->s,&vchSig[65-(nBitsS+7)/8]);
 258             fOk = true;
 259         }
 260         ECDSA_SIG_free(sig);
 261         return fOk;
 262     }
 263
 264     // reconstruct public key from a compact signature
 265     // This is only slightly more CPU intensive than just verifying it.
 266     // If this function succeeds, the recovered public key is guaranteed to be valid
 267     // (the signature is a valid signature of the given data for that key)
 268     bool SetCompactSignature(uint256 hash, const std::vector<unsigned char>& vchSig)
 269     {
 270         if (vchSig.size() != 65)
 271             return false;
 272         int nV = vchSig[0];
 273         if (nV<27 || nV>=35)
 274             return false;
 275         ECDSA_SIG *sig = ECDSA_SIG_new();
 276         BN_bin2bn(&vchSig[1],32,sig->r);
 277         BN_bin2bn(&vchSig[33],32,sig->s);
 278
 279         EC_KEY_free(pkey);
 280         pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
 281         if (nV >= 31)
 282         {
 283             SetCompressedPubKey();
 284             nV -= 4;
 285         }
 286         if (ECDSA_SIG_recover_key_GFp(pkey, sig, (unsigned char*)&hash, sizeof(hash), nV - 27, 0) == 1)
 287         {
 288             fSet = true;
 289             ECDSA_SIG_free(sig);
 290             return true;
 291         }
 292         return false;
 293     }
 294
 295     bool Verify(uint256 hash, const std::vector<unsigned char>& vchSig)
 296     {
 297         // -1 = error, 0 = bad sig, 1 = good
 298         if (ECDSA_verify(0, (unsigned char*)&hash, sizeof(hash), &vchSig[0], vchSig.size(), pkey) != 1)
 299             return false;
 300         return true;
 301     }
 302
 303     // Verify a compact signature
 304     bool VerifyCompact(uint256 hash, const std::vector<unsigned char>& vchSig)
 305     {
 306         CKey key;
 307         if (!key.SetCompactSignature(hash, vchSig))
 308             return false;
 309         if (GetPubKey() != key.GetPubKey())
 310             return false;
 311         return true;
 312     }
 313
 314     bool IsValid()
 315     {
 316         if (!fSet)
 317             return false;
 318
 319         bool fCompr;
 320         CSecret secret = GetSecret(fCompr);
 321         CKey key2;
 322         key2.SetSecret(secret, fCompr);
 323         return GetPubKey() == key2.GetPubKey();
 324     }
 325 };
 326
 327 #endif