1 // Copyright (c) 2009-2012 The Bitcoin developers
2 // Distributed under the MIT/X11 software license, see the accompanying
3 // file license.txt or http://www.opensource.org/licenses/mit-license.php.
5 #include <openssl/ecdsa.h>
6 #include <openssl/obj_mac.h>
10 // Generate a private key from just the secret parameter
11 int EC_KEY_regenerate_key(EC_KEY *eckey, BIGNUM *priv_key)
15 EC_POINT *pub_key = NULL;
19 const EC_GROUP *group = EC_KEY_get0_group(eckey);
21 if ((ctx = BN_CTX_new()) == NULL)
24 pub_key = EC_POINT_new(group);
29 if (!EC_POINT_mul(group, pub_key, priv_key, NULL, NULL, ctx))
32 EC_KEY_set_private_key(eckey,priv_key);
33 EC_KEY_set_public_key(eckey,pub_key);
40 EC_POINT_free(pub_key);
47 // Perform ECDSA key recovery (see SEC1 4.1.6) for curves over (mod p)-fields
48 // recid selects which key is recovered
49 // if check is nonzero, additional checks are performed
50 int ECDSA_SIG_recover_key_GFp(EC_KEY *eckey, ECDSA_SIG *ecsig, const unsigned char *msg, int msglen, int recid, int check)
71 const EC_GROUP *group = EC_KEY_get0_group(eckey);
72 if ((ctx = BN_CTX_new()) == NULL) { ret = -1; goto err; }
74 order = BN_CTX_get(ctx);
75 if (!EC_GROUP_get_order(group, order, ctx)) { ret = -2; goto err; }
77 if (!BN_copy(x, order)) { ret=-1; goto err; }
78 if (!BN_mul_word(x, i)) { ret=-1; goto err; }
79 if (!BN_add(x, x, ecsig->r)) { ret=-1; goto err; }
80 field = BN_CTX_get(ctx);
81 if (!EC_GROUP_get_curve_GFp(group, field, NULL, NULL, ctx)) { ret=-2; goto err; }
82 if (BN_cmp(x, field) >= 0) { ret=0; goto err; }
83 if ((R = EC_POINT_new(group)) == NULL) { ret = -2; goto err; }
84 if (!EC_POINT_set_compressed_coordinates_GFp(group, R, x, recid % 2, ctx)) { ret=0; goto err; }
87 if ((O = EC_POINT_new(group)) == NULL) { ret = -2; goto err; }
88 if (!EC_POINT_mul(group, O, NULL, R, order, ctx)) { ret=-2; goto err; }
89 if (!EC_POINT_is_at_infinity(group, O)) { ret = 0; goto err; }
91 if ((Q = EC_POINT_new(group)) == NULL) { ret = -2; goto err; }
92 n = EC_GROUP_get_degree(group);
94 if (!BN_bin2bn(msg, msglen, e)) { ret=-1; goto err; }
95 if (8*msglen > n) BN_rshift(e, e, 8-(n & 7));
96 zero = BN_CTX_get(ctx);
97 if (!BN_zero(zero)) { ret=-1; goto err; }
98 if (!BN_mod_sub(e, zero, e, order, ctx)) { ret=-1; goto err; }
100 if (!BN_mod_inverse(rr, ecsig->r, order, ctx)) { ret=-1; goto err; }
101 sor = BN_CTX_get(ctx);
102 if (!BN_mod_mul(sor, ecsig->s, rr, order, ctx)) { ret=-1; goto err; }
103 eor = BN_CTX_get(ctx);
104 if (!BN_mod_mul(eor, e, rr, order, ctx)) { ret=-1; goto err; }
105 if (!EC_POINT_mul(group, Q, eor, R, sor, ctx)) { ret=-2; goto err; }
106 if (!EC_KEY_set_public_key(eckey, Q)) { ret=-2; goto err; }
115 if (R != NULL) EC_POINT_free(R);
116 if (O != NULL) EC_POINT_free(O);
117 if (Q != NULL) EC_POINT_free(Q);
121 void CKey::SetCompressedPubKey()
123 EC_KEY_set_conv_form(pkey, POINT_CONVERSION_COMPRESSED);
124 fCompressedPubKey = true;
129 fCompressedPubKey = false;
130 pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
132 throw key_error("CKey::CKey() : EC_KEY_new_by_curve_name failed");
141 CKey::CKey(const CKey& b)
143 pkey = EC_KEY_dup(b.pkey);
145 throw key_error("CKey::CKey(const CKey&) : EC_KEY_dup failed");
149 CKey& CKey::operator=(const CKey& b)
151 if (!EC_KEY_copy(pkey, b.pkey))
152 throw key_error("CKey::operator=(const CKey&) : EC_KEY_copy failed");
162 bool CKey::IsNull() const
167 bool CKey::IsCompressed() const
169 return fCompressedPubKey;
172 void CKey::MakeNewKey(bool fCompressed)
174 if (!EC_KEY_generate_key(pkey))
175 throw key_error("CKey::MakeNewKey() : EC_KEY_generate_key failed");
177 SetCompressedPubKey();
181 bool CKey::SetPrivKey(const CPrivKey& vchPrivKey)
183 const unsigned char* pbegin = &vchPrivKey[0];
184 if (!d2i_ECPrivateKey(&pkey, &pbegin, vchPrivKey.size()))
190 bool CKey::SetSecret(const CSecret& vchSecret, bool fCompressed)
193 pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
195 throw key_error("CKey::SetSecret() : EC_KEY_new_by_curve_name failed");
196 if (vchSecret.size() != 32)
197 throw key_error("CKey::SetSecret() : secret must be 32 bytes");
198 BIGNUM *bn = BN_bin2bn(&vchSecret[0],32,BN_new());
200 throw key_error("CKey::SetSecret() : BN_bin2bn failed");
201 if (!EC_KEY_regenerate_key(pkey,bn))
204 throw key_error("CKey::SetSecret() : EC_KEY_regenerate_key failed");
208 if (fCompressed || fCompressedPubKey)
209 SetCompressedPubKey();
213 CSecret CKey::GetSecret(bool &fCompressed) const
217 const BIGNUM *bn = EC_KEY_get0_private_key(pkey);
218 int nBytes = BN_num_bytes(bn);
220 throw key_error("CKey::GetSecret() : EC_KEY_get0_private_key failed");
221 int n=BN_bn2bin(bn,&vchRet[32 - nBytes]);
223 throw key_error("CKey::GetSecret(): BN_bn2bin failed");
224 fCompressed = fCompressedPubKey;
228 CPrivKey CKey::GetPrivKey() const
230 int nSize = i2d_ECPrivateKey(pkey, NULL);
232 throw key_error("CKey::GetPrivKey() : i2d_ECPrivateKey failed");
233 CPrivKey vchPrivKey(nSize, 0);
234 unsigned char* pbegin = &vchPrivKey[0];
235 if (i2d_ECPrivateKey(pkey, &pbegin) != nSize)
236 throw key_error("CKey::GetPrivKey() : i2d_ECPrivateKey returned unexpected size");
240 bool CKey::SetPubKey(const std::vector<unsigned char>& vchPubKey)
242 const unsigned char* pbegin = &vchPubKey[0];
243 if (!o2i_ECPublicKey(&pkey, &pbegin, vchPubKey.size()))
246 if (vchPubKey.size() == 33)
247 SetCompressedPubKey();
251 std::vector<unsigned char> CKey::GetPubKey() const
253 int nSize = i2o_ECPublicKey(pkey, NULL);
255 throw key_error("CKey::GetPubKey() : i2o_ECPublicKey failed");
256 std::vector<unsigned char> vchPubKey(nSize, 0);
257 unsigned char* pbegin = &vchPubKey[0];
258 if (i2o_ECPublicKey(pkey, &pbegin) != nSize)
259 throw key_error("CKey::GetPubKey() : i2o_ECPublicKey returned unexpected size");
263 bool CKey::Sign(uint256 hash, std::vector<unsigned char>& vchSig)
265 unsigned int nSize = ECDSA_size(pkey);
266 vchSig.resize(nSize); // Make sure it is big enough
267 if (!ECDSA_sign(0, (unsigned char*)&hash, sizeof(hash), &vchSig[0], &nSize, pkey))
272 vchSig.resize(nSize); // Shrink to fit actual size
276 // create a compact signature (65 bytes), which allows reconstructing the used public key
277 // The format is one header byte, followed by two times 32 bytes for the serialized r and s values.
278 // The header byte: 0x1B = first key with even y, 0x1C = first key with odd y,
279 // 0x1D = second key with even y, 0x1E = second key with odd y
280 bool CKey::SignCompact(uint256 hash, std::vector<unsigned char>& vchSig)
283 ECDSA_SIG *sig = ECDSA_do_sign((unsigned char*)&hash, sizeof(hash), pkey);
288 int nBitsR = BN_num_bits(sig->r);
289 int nBitsS = BN_num_bits(sig->s);
290 if (nBitsR <= 256 && nBitsS <= 256)
293 for (int i=0; i<4; i++)
297 if (fCompressedPubKey)
298 keyRec.SetCompressedPubKey();
299 if (ECDSA_SIG_recover_key_GFp(keyRec.pkey, sig, (unsigned char*)&hash, sizeof(hash), i, 1) == 1)
300 if (keyRec.GetPubKey() == this->GetPubKey())
308 throw key_error("CKey::SignCompact() : unable to construct recoverable key");
310 vchSig[0] = nRecId+27+(fCompressedPubKey ? 4 : 0);
311 BN_bn2bin(sig->r,&vchSig[33-(nBitsR+7)/8]);
312 BN_bn2bin(sig->s,&vchSig[65-(nBitsS+7)/8]);
319 // reconstruct public key from a compact signature
320 // This is only slightly more CPU intensive than just verifying it.
321 // If this function succeeds, the recovered public key is guaranteed to be valid
322 // (the signature is a valid signature of the given data for that key)
323 bool CKey::SetCompactSignature(uint256 hash, const std::vector<unsigned char>& vchSig)
325 if (vchSig.size() != 65)
330 ECDSA_SIG *sig = ECDSA_SIG_new();
331 BN_bin2bn(&vchSig[1],32,sig->r);
332 BN_bin2bn(&vchSig[33],32,sig->s);
335 pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
338 SetCompressedPubKey();
341 if (ECDSA_SIG_recover_key_GFp(pkey, sig, (unsigned char*)&hash, sizeof(hash), nV - 27, 0) == 1)
350 bool CKey::Verify(uint256 hash, const std::vector<unsigned char>& vchSig)
352 // -1 = error, 0 = bad sig, 1 = good
353 if (ECDSA_verify(0, (unsigned char*)&hash, sizeof(hash), &vchSig[0], vchSig.size(), pkey) != 1)
358 bool CKey::VerifyCompact(uint256 hash, const std::vector<unsigned char>& vchSig)
361 if (!key.SetCompactSignature(hash, vchSig))
363 if (GetPubKey() != key.GetPubKey())
374 CSecret secret = GetSecret(fCompr);
376 key2.SetSecret(secret, fCompr);
377 return GetPubKey() == key2.GetPubKey();