1 // Copyright (c) 2009-2012 The Bitcoin developers
2 // Distributed under the MIT/X11 software license, see the accompanying
3 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
7 #include <openssl/ecdsa.h>
8 #include <openssl/obj_mac.h>
12 // Generate a private key from just the secret parameter
13 int EC_KEY_regenerate_key(EC_KEY *eckey, BIGNUM *priv_key)
17 EC_POINT *pub_key = NULL;
21 const EC_GROUP *group = EC_KEY_get0_group(eckey);
23 if ((ctx = BN_CTX_new()) == NULL)
26 pub_key = EC_POINT_new(group);
31 if (!EC_POINT_mul(group, pub_key, priv_key, NULL, NULL, ctx))
34 EC_KEY_set_private_key(eckey,priv_key);
35 EC_KEY_set_public_key(eckey,pub_key);
42 EC_POINT_free(pub_key);
49 // Perform ECDSA key recovery (see SEC1 4.1.6) for curves over (mod p)-fields
50 // recid selects which key is recovered
51 // if check is non-zero, additional checks are performed
52 int ECDSA_SIG_recover_key_GFp(EC_KEY *eckey, ECDSA_SIG *ecsig, const unsigned char *msg, int msglen, int recid, int check)
73 const EC_GROUP *group = EC_KEY_get0_group(eckey);
74 if ((ctx = BN_CTX_new()) == NULL) { ret = -1; goto err; }
76 order = BN_CTX_get(ctx);
77 if (!EC_GROUP_get_order(group, order, ctx)) { ret = -2; goto err; }
79 if (!BN_copy(x, order)) { ret=-1; goto err; }
80 if (!BN_mul_word(x, i)) { ret=-1; goto err; }
81 if (!BN_add(x, x, ecsig->r)) { ret=-1; goto err; }
82 field = BN_CTX_get(ctx);
83 if (!EC_GROUP_get_curve_GFp(group, field, NULL, NULL, ctx)) { ret=-2; goto err; }
84 if (BN_cmp(x, field) >= 0) { ret=0; goto err; }
85 if ((R = EC_POINT_new(group)) == NULL) { ret = -2; goto err; }
86 if (!EC_POINT_set_compressed_coordinates_GFp(group, R, x, recid % 2, ctx)) { ret=0; goto err; }
89 if ((O = EC_POINT_new(group)) == NULL) { ret = -2; goto err; }
90 if (!EC_POINT_mul(group, O, NULL, R, order, ctx)) { ret=-2; goto err; }
91 if (!EC_POINT_is_at_infinity(group, O)) { ret = 0; goto err; }
93 if ((Q = EC_POINT_new(group)) == NULL) { ret = -2; goto err; }
94 n = EC_GROUP_get_degree(group);
96 if (!BN_bin2bn(msg, msglen, e)) { ret=-1; goto err; }
97 if (8*msglen > n) BN_rshift(e, e, 8-(n & 7));
98 zero = BN_CTX_get(ctx);
99 if (!BN_zero(zero)) { ret=-1; goto err; }
100 if (!BN_mod_sub(e, zero, e, order, ctx)) { ret=-1; goto err; }
101 rr = BN_CTX_get(ctx);
102 if (!BN_mod_inverse(rr, ecsig->r, order, ctx)) { ret=-1; goto err; }
103 sor = BN_CTX_get(ctx);
104 if (!BN_mod_mul(sor, ecsig->s, rr, order, ctx)) { ret=-1; goto err; }
105 eor = BN_CTX_get(ctx);
106 if (!BN_mod_mul(eor, e, rr, order, ctx)) { ret=-1; goto err; }
107 if (!EC_POINT_mul(group, Q, eor, R, sor, ctx)) { ret=-2; goto err; }
108 if (!EC_KEY_set_public_key(eckey, Q)) { ret=-2; goto err; }
117 if (R != NULL) EC_POINT_free(R);
118 if (O != NULL) EC_POINT_free(O);
119 if (Q != NULL) EC_POINT_free(Q);
123 void CKey::SetCompressedPubKey()
125 EC_KEY_set_conv_form(pkey, POINT_CONVERSION_COMPRESSED);
126 fCompressedPubKey = true;
131 fCompressedPubKey = false;
134 pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
136 throw key_error("CKey::CKey() : EC_KEY_new_by_curve_name failed");
146 CKey::CKey(const CKey& b)
148 pkey = EC_KEY_dup(b.pkey);
150 throw key_error("CKey::CKey(const CKey&) : EC_KEY_dup failed");
154 CKey& CKey::operator=(const CKey& b)
156 if (!EC_KEY_copy(pkey, b.pkey))
157 throw key_error("CKey::operator=(const CKey&) : EC_KEY_copy failed");
167 bool CKey::IsNull() const
172 bool CKey::IsCompressed() const
174 return fCompressedPubKey;
177 void CKey::MakeNewKey(bool fCompressed)
179 if (!EC_KEY_generate_key(pkey))
180 throw key_error("CKey::MakeNewKey() : EC_KEY_generate_key failed");
182 SetCompressedPubKey();
186 bool CKey::SetPrivKey(const CPrivKey& vchPrivKey)
188 const unsigned char* pbegin = &vchPrivKey[0];
189 if (d2i_ECPrivateKey(&pkey, &pbegin, vchPrivKey.size()))
191 // In testing, d2i_ECPrivateKey can return true
192 // but fill in pkey with a key that fails
193 // EC_KEY_check_key, so:
194 if (EC_KEY_check_key(pkey))
200 // If vchPrivKey data is bad d2i_ECPrivateKey() can
201 // leave pkey in a state where calling EC_KEY_free()
202 // crashes. To avoid that, set pkey to NULL and
203 // leak the memory (a leak is better than a crash)
209 bool CKey::SetSecret(const CSecret& vchSecret, bool fCompressed)
212 pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
214 throw key_error("CKey::SetSecret() : EC_KEY_new_by_curve_name failed");
215 if (vchSecret.size() != 32)
216 throw key_error("CKey::SetSecret() : secret must be 32 bytes");
217 BIGNUM *bn = BN_bin2bn(&vchSecret[0],32,BN_new());
219 throw key_error("CKey::SetSecret() : BN_bin2bn failed");
220 if (!EC_KEY_regenerate_key(pkey,bn))
223 throw key_error("CKey::SetSecret() : EC_KEY_regenerate_key failed");
227 if (fCompressed || fCompressedPubKey)
228 SetCompressedPubKey();
232 CSecret CKey::GetSecret(bool &fCompressed) const
236 const BIGNUM *bn = EC_KEY_get0_private_key(pkey);
237 int nBytes = BN_num_bytes(bn);
239 throw key_error("CKey::GetSecret() : EC_KEY_get0_private_key failed");
240 int n=BN_bn2bin(bn,&vchRet[32 - nBytes]);
242 throw key_error("CKey::GetSecret(): BN_bn2bin failed");
243 fCompressed = fCompressedPubKey;
247 CPrivKey CKey::GetPrivKey() const
249 int nSize = i2d_ECPrivateKey(pkey, NULL);
251 throw key_error("CKey::GetPrivKey() : i2d_ECPrivateKey failed");
252 CPrivKey vchPrivKey(nSize, 0);
253 unsigned char* pbegin = &vchPrivKey[0];
254 if (i2d_ECPrivateKey(pkey, &pbegin) != nSize)
255 throw key_error("CKey::GetPrivKey() : i2d_ECPrivateKey returned unexpected size");
259 bool CKey::SetPubKey(const CPubKey& vchPubKey)
261 const unsigned char* pbegin = &vchPubKey.vchPubKey[0];
262 if (o2i_ECPublicKey(&pkey, &pbegin, vchPubKey.vchPubKey.size()))
265 if (vchPubKey.vchPubKey.size() == 33)
266 SetCompressedPubKey();
274 CPubKey CKey::GetPubKey() const
276 int nSize = i2o_ECPublicKey(pkey, NULL);
278 throw key_error("CKey::GetPubKey() : i2o_ECPublicKey failed");
279 std::vector<unsigned char> vchPubKey(nSize, 0);
280 unsigned char* pbegin = &vchPubKey[0];
281 if (i2o_ECPublicKey(pkey, &pbegin) != nSize)
282 throw key_error("CKey::GetPubKey() : i2o_ECPublicKey returned unexpected size");
283 return CPubKey(vchPubKey);
286 bool CKey::Sign(uint256 hash, std::vector<unsigned char>& vchSig)
288 unsigned int nSize = ECDSA_size(pkey);
289 vchSig.resize(nSize); // Make sure it is big enough
290 if (!ECDSA_sign(0, (unsigned char*)&hash, sizeof(hash), &vchSig[0], &nSize, pkey))
295 vchSig.resize(nSize); // Shrink to fit actual size
299 // create a compact signature (65 bytes), which allows reconstructing the used public key
300 // The format is one header byte, followed by two times 32 bytes for the serialized r and s values.
301 // The header byte: 0x1B = first key with even y, 0x1C = first key with odd y,
302 // 0x1D = second key with even y, 0x1E = second key with odd y
303 bool CKey::SignCompact(uint256 hash, std::vector<unsigned char>& vchSig)
306 ECDSA_SIG *sig = ECDSA_do_sign((unsigned char*)&hash, sizeof(hash), pkey);
311 int nBitsR = BN_num_bits(sig->r);
312 int nBitsS = BN_num_bits(sig->s);
313 if (nBitsR <= 256 && nBitsS <= 256)
316 for (int i=0; i<4; i++)
320 if (fCompressedPubKey)
321 keyRec.SetCompressedPubKey();
322 if (ECDSA_SIG_recover_key_GFp(keyRec.pkey, sig, (unsigned char*)&hash, sizeof(hash), i, 1) == 1)
323 if (keyRec.GetPubKey() == this->GetPubKey())
331 throw key_error("CKey::SignCompact() : unable to construct recoverable key");
333 vchSig[0] = nRecId+27+(fCompressedPubKey ? 4 : 0);
334 BN_bn2bin(sig->r,&vchSig[33-(nBitsR+7)/8]);
335 BN_bn2bin(sig->s,&vchSig[65-(nBitsS+7)/8]);
342 // reconstruct public key from a compact signature
343 // This is only slightly more CPU intensive than just verifying it.
344 // If this function succeeds, the recovered public key is guaranteed to be valid
345 // (the signature is a valid signature of the given data for that key)
346 bool CKey::SetCompactSignature(uint256 hash, const std::vector<unsigned char>& vchSig)
348 if (vchSig.size() != 65)
353 ECDSA_SIG *sig = ECDSA_SIG_new();
354 BN_bin2bn(&vchSig[1],32,sig->r);
355 BN_bin2bn(&vchSig[33],32,sig->s);
358 pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
361 SetCompressedPubKey();
364 if (ECDSA_SIG_recover_key_GFp(pkey, sig, (unsigned char*)&hash, sizeof(hash), nV - 27, 0) == 1)
373 bool CKey::Verify(uint256 hash, const std::vector<unsigned char>& vchSig)
375 // -1 = error, 0 = bad sig, 1 = good
376 if (ECDSA_verify(0, (unsigned char*)&hash, sizeof(hash), &vchSig[0], vchSig.size(), pkey) != 1)
382 bool CKey::VerifyCompact(uint256 hash, const std::vector<unsigned char>& vchSig)
385 if (!key.SetCompactSignature(hash, vchSig))
387 if (GetPubKey() != key.GetPubKey())
398 if (!EC_KEY_check_key(pkey))
402 CSecret secret = GetSecret(fCompr);
404 key2.SetSecret(secret, fCompr);
405 return GetPubKey() == key2.GetPubKey();