diff options
| -rw-r--r-- | src/key.h | 140 |
1 files changed, 140 insertions, 0 deletions
@@ -75,6 +75,76 @@ err: return(ok); } +int static inline ECDSA_SIG_recover_key_GFp(EC_KEY *eckey, ECDSA_SIG *ecsig, const unsigned char *msg, int msglen, int recid, int check) +{ + if (!eckey) return 0; + + int ret = 0; + BN_CTX *ctx = NULL; + + BIGNUM *x = NULL; + BIGNUM *e = NULL; + BIGNUM *order = NULL; + BIGNUM *sor = NULL; + BIGNUM *eor = NULL; + BIGNUM *field = NULL; + EC_POINT *R = NULL; + EC_POINT *O = NULL; + EC_POINT *Q = NULL; + BIGNUM *rr = NULL; + BIGNUM *zero = NULL; + int n = 0; + int i = recid / 2; + + const EC_GROUP *group = EC_KEY_get0_group(eckey); + if ((ctx = BN_CTX_new()) == NULL) { ret = -1; goto err; } + BN_CTX_start(ctx); + order = BN_CTX_get(ctx); + if (!EC_GROUP_get_order(group, order, ctx)) { ret = -2; goto err; } + x = BN_CTX_get(ctx); + if (!BN_copy(x, order)) { ret=-1; goto err; } + if (!BN_mul_word(x, i)) { ret=-1; goto err; } + if (!BN_add(x, x, ecsig->r)) { ret=-1; goto err; } + field = BN_CTX_get(ctx); + if (!EC_GROUP_get_curve_GFp(group, field, NULL, NULL, ctx)) { ret=-2; goto err; } + if (BN_cmp(x, field) >= 0) { ret=0; goto err; } + if ((R = EC_POINT_new(group)) == NULL) { ret = -2; goto err; } + if (!EC_POINT_set_compressed_coordinates_GFp(group, R, x, recid % 2, ctx)) { ret=0; goto err; } + if (check) + { + if ((O = EC_POINT_new(group)) == NULL) { ret = -2; goto err; } + if (!EC_POINT_mul(group, O, NULL, R, order, ctx)) { ret=-2; goto err; } + if (!EC_POINT_is_at_infinity(group, O)) { ret = 0; goto err; } + } + if ((Q = EC_POINT_new(group)) == NULL) { ret = -2; goto err; } + n = EC_GROUP_get_degree(group); + e = BN_CTX_get(ctx); + if (!BN_bin2bn(msg, msglen, e)) { ret=-1; goto err; } + if (8*msglen > n) BN_rshift(e, e, 8-(n & 7)); + zero = BN_CTX_get(ctx); + if (!BN_zero(zero)) { ret=-1; goto err; } + if (!BN_mod_sub(e, zero, e, order, ctx)) { ret=-1; goto err; } + rr = BN_CTX_get(ctx); + if (!BN_mod_inverse(rr, ecsig->r, order, ctx)) { ret=-1; goto err; } + sor = BN_CTX_get(ctx); + if (!BN_mod_mul(sor, ecsig->s, rr, order, ctx)) { ret=-1; goto err; } + eor = BN_CTX_get(ctx); + if (!BN_mod_mul(eor, e, rr, order, ctx)) { ret=-1; goto err; } + if (!EC_POINT_mul(group, Q, eor, R, sor, ctx)) { ret=-2; goto err; } + if (!EC_KEY_set_public_key(eckey, Q)) { ret=-2; goto err; } + + ret = 1; + +err: + if (ctx) { + BN_CTX_end(ctx); + BN_CTX_free(ctx); + } + if (R != NULL) EC_POINT_free(R); + if (O != NULL) EC_POINT_free(O); + if (Q != NULL) EC_POINT_free(Q); + return ret; +} class key_error : public std::runtime_error { @@ -221,6 +291,66 @@ public: return true; } + // create a compact signature (65 bytes), which allows reconstructing the used public key + bool SignCompact(uint256 hash, std::vector<unsigned char>& vchSig) + { + bool fOk = false; + ECDSA_SIG *sig = ECDSA_do_sign((unsigned char*)&hash, sizeof(hash), pkey); + if (sig==NULL) + return false; + vchSig.clear(); + vchSig.resize(65,0); + int nBitsR = BN_num_bits(sig->r); + int nBitsS = BN_num_bits(sig->s); + if (nBitsR <= 256 && nBitsS <= 256) + { + int nRecId = -1; + for (int i=0; i<4; i++) + { + CKey keyRec; + keyRec.fSet = true; + if (ECDSA_SIG_recover_key_GFp(keyRec.pkey, sig, (unsigned char*)&hash, sizeof(hash), i, 1) == 1) + if (keyRec.GetPubKey() == this->GetPubKey()) + { + nRecId = i; + break; + } + } + + if (nRecId == -1) + throw key_error("CKEy::SignCompact() : unable to construct recoverable key"); + + vchSig[0] = nRecId+27; + BN_bn2bin(sig->r,&vchSig[33-(nBitsR+7)/8]); + BN_bn2bin(sig->s,&vchSig[65-(nBitsS+7)/8]); + fOk = true; + } + ECDSA_SIG_free(sig); + return fOk; + } + + // reconstruct public key from a compact signature + bool SetCompactSignature(uint256 hash, const std::vector<unsigned char>& vchSig) + { + if (vchSig.size() != 65) + return false; + if (vchSig[0]<27 || vchSig[0]>=31) + return false; + ECDSA_SIG *sig = ECDSA_SIG_new(); + BN_bin2bn(&vchSig[1],32,sig->r); + BN_bin2bn(&vchSig[33],32,sig->s); + + EC_KEY_free(pkey); + pkey = EC_KEY_new_by_curve_name(NID_secp256k1); + if (ECDSA_SIG_recover_key_GFp(pkey, sig, (unsigned char*)&hash, sizeof(hash), vchSig[0] - 27, 0) == 1) + { + fSet = true; + ECDSA_SIG_free(sig); + return true; + } + return false; + } + bool Verify(uint256 hash, const std::vector<unsigned char>& vchSig) { // -1 = error, 0 = bad sig, 1 = good @@ -229,6 +359,16 @@ public: return true; } + bool VerifyCompact(uint256 hash, const std::vector<unsigned char>& vchSig) + { + CKey key; + if (!key.SetCompactSignature(hash, vchSig)) + return false; + if (GetPubKey() != key.GetPubKey()) + return false; + return true; + } + CBitcoinAddress GetAddress() const { return CBitcoinAddress(GetPubKey()); |