Cory Fields
10 years ago
4 changed files with 384 additions and 330 deletions
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// Copyright (c) 2009-2014 The Bitcoin developers
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// Distributed under the MIT/X11 software license, see the accompanying
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// file COPYING or http://www.opensource.org/licenses/mit-license.php.
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#include "ecwrapper.h" |
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#include "serialize.h" |
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#include "uint256.h" |
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#include <openssl/bn.h> |
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#include <openssl/ecdsa.h> |
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#include <openssl/obj_mac.h> |
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namespace { |
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// Generate a private key from just the secret parameter
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int EC_KEY_regenerate_key(EC_KEY *eckey, BIGNUM *priv_key) |
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{ |
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int ok = 0; |
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BN_CTX *ctx = NULL; |
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EC_POINT *pub_key = NULL; |
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if (!eckey) return 0; |
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const EC_GROUP *group = EC_KEY_get0_group(eckey); |
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if ((ctx = BN_CTX_new()) == NULL) |
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goto err; |
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pub_key = EC_POINT_new(group); |
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if (pub_key == NULL) |
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goto err; |
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if (!EC_POINT_mul(group, pub_key, priv_key, NULL, NULL, ctx)) |
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goto err; |
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EC_KEY_set_private_key(eckey,priv_key); |
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EC_KEY_set_public_key(eckey,pub_key); |
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ok = 1; |
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err: |
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if (pub_key) |
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EC_POINT_free(pub_key); |
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if (ctx != NULL) |
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BN_CTX_free(ctx); |
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return(ok); |
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} |
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// Perform ECDSA key recovery (see SEC1 4.1.6) for curves over (mod p)-fields
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// recid selects which key is recovered
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// if check is non-zero, additional checks are performed
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int ECDSA_SIG_recover_key_GFp(EC_KEY *eckey, ECDSA_SIG *ecsig, const unsigned char *msg, int msglen, int recid, int check) |
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{ |
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if (!eckey) return 0; |
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int ret = 0; |
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BN_CTX *ctx = NULL; |
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BIGNUM *x = NULL; |
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BIGNUM *e = NULL; |
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BIGNUM *order = NULL; |
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BIGNUM *sor = NULL; |
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BIGNUM *eor = NULL; |
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BIGNUM *field = NULL; |
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EC_POINT *R = NULL; |
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EC_POINT *O = NULL; |
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EC_POINT *Q = NULL; |
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BIGNUM *rr = NULL; |
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BIGNUM *zero = NULL; |
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int n = 0; |
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int i = recid / 2; |
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const EC_GROUP *group = EC_KEY_get0_group(eckey); |
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if ((ctx = BN_CTX_new()) == NULL) { ret = -1; goto err; } |
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BN_CTX_start(ctx); |
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order = BN_CTX_get(ctx); |
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if (!EC_GROUP_get_order(group, order, ctx)) { ret = -2; goto err; } |
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x = BN_CTX_get(ctx); |
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if (!BN_copy(x, order)) { ret=-1; goto err; } |
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if (!BN_mul_word(x, i)) { ret=-1; goto err; } |
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if (!BN_add(x, x, ecsig->r)) { ret=-1; goto err; } |
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field = BN_CTX_get(ctx); |
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if (!EC_GROUP_get_curve_GFp(group, field, NULL, NULL, ctx)) { ret=-2; goto err; } |
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if (BN_cmp(x, field) >= 0) { ret=0; goto err; } |
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if ((R = EC_POINT_new(group)) == NULL) { ret = -2; goto err; } |
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if (!EC_POINT_set_compressed_coordinates_GFp(group, R, x, recid % 2, ctx)) { ret=0; goto err; } |
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if (check) |
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{ |
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if ((O = EC_POINT_new(group)) == NULL) { ret = -2; goto err; } |
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if (!EC_POINT_mul(group, O, NULL, R, order, ctx)) { ret=-2; goto err; } |
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if (!EC_POINT_is_at_infinity(group, O)) { ret = 0; goto err; } |
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} |
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if ((Q = EC_POINT_new(group)) == NULL) { ret = -2; goto err; } |
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n = EC_GROUP_get_degree(group); |
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e = BN_CTX_get(ctx); |
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if (!BN_bin2bn(msg, msglen, e)) { ret=-1; goto err; } |
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if (8*msglen > n) BN_rshift(e, e, 8-(n & 7)); |
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zero = BN_CTX_get(ctx); |
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if (!BN_zero(zero)) { ret=-1; goto err; } |
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if (!BN_mod_sub(e, zero, e, order, ctx)) { ret=-1; goto err; } |
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rr = BN_CTX_get(ctx); |
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if (!BN_mod_inverse(rr, ecsig->r, order, ctx)) { ret=-1; goto err; } |
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sor = BN_CTX_get(ctx); |
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if (!BN_mod_mul(sor, ecsig->s, rr, order, ctx)) { ret=-1; goto err; } |
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eor = BN_CTX_get(ctx); |
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if (!BN_mod_mul(eor, e, rr, order, ctx)) { ret=-1; goto err; } |
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if (!EC_POINT_mul(group, Q, eor, R, sor, ctx)) { ret=-2; goto err; } |
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if (!EC_KEY_set_public_key(eckey, Q)) { ret=-2; goto err; } |
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ret = 1; |
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err: |
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if (ctx) { |
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BN_CTX_end(ctx); |
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BN_CTX_free(ctx); |
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} |
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if (R != NULL) EC_POINT_free(R); |
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if (O != NULL) EC_POINT_free(O); |
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if (Q != NULL) EC_POINT_free(Q); |
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return ret; |
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} |
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} // anon namespace
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CECKey::CECKey() { |
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pkey = EC_KEY_new_by_curve_name(NID_secp256k1); |
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assert(pkey != NULL); |
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} |
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CECKey::~CECKey() { |
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EC_KEY_free(pkey); |
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} |
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void CECKey::GetSecretBytes(unsigned char vch[32]) const { |
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const BIGNUM *bn = EC_KEY_get0_private_key(pkey); |
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assert(bn); |
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int nBytes = BN_num_bytes(bn); |
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int n=BN_bn2bin(bn,&vch[32 - nBytes]); |
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assert(n == nBytes); |
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memset(vch, 0, 32 - nBytes); |
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} |
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void CECKey::SetSecretBytes(const unsigned char vch[32]) { |
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bool ret; |
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BIGNUM bn; |
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BN_init(&bn); |
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ret = BN_bin2bn(vch, 32, &bn) != NULL; |
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assert(ret); |
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ret = EC_KEY_regenerate_key(pkey, &bn) != 0; |
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assert(ret); |
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BN_clear_free(&bn); |
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} |
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int CECKey::GetPrivKeySize(bool fCompressed) { |
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EC_KEY_set_conv_form(pkey, fCompressed ? POINT_CONVERSION_COMPRESSED : POINT_CONVERSION_UNCOMPRESSED); |
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return i2d_ECPrivateKey(pkey, NULL); |
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} |
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int CECKey::GetPrivKey(unsigned char* privkey, bool fCompressed) { |
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EC_KEY_set_conv_form(pkey, fCompressed ? POINT_CONVERSION_COMPRESSED : POINT_CONVERSION_UNCOMPRESSED); |
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return i2d_ECPrivateKey(pkey, &privkey); |
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} |
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bool CECKey::SetPrivKey(const unsigned char* privkey, size_t size, bool fSkipCheck) { |
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if (d2i_ECPrivateKey(&pkey, &privkey, size)) { |
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if(fSkipCheck) |
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return true; |
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// d2i_ECPrivateKey returns true if parsing succeeds.
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// This doesn't necessarily mean the key is valid.
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if (EC_KEY_check_key(pkey)) |
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return true; |
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} |
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return false; |
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} |
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void CECKey::GetPubKey(std::vector<unsigned char> &pubkey, bool fCompressed) { |
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EC_KEY_set_conv_form(pkey, fCompressed ? POINT_CONVERSION_COMPRESSED : POINT_CONVERSION_UNCOMPRESSED); |
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int nSize = i2o_ECPublicKey(pkey, NULL); |
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assert(nSize); |
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assert(nSize <= 65); |
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pubkey.clear(); |
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pubkey.resize(nSize); |
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unsigned char *pbegin(begin_ptr(pubkey)); |
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int nSize2 = i2o_ECPublicKey(pkey, &pbegin); |
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assert(nSize == nSize2); |
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} |
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bool CECKey::SetPubKey(const unsigned char* pubkey, size_t size) { |
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return o2i_ECPublicKey(&pkey, &pubkey, size) != NULL; |
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} |
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bool CECKey::Sign(const uint256 &hash, std::vector<unsigned char>& vchSig, bool lowS) { |
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vchSig.clear(); |
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ECDSA_SIG *sig = ECDSA_do_sign((unsigned char*)&hash, sizeof(hash), pkey); |
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if (sig == NULL) |
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return false; |
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BN_CTX *ctx = BN_CTX_new(); |
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BN_CTX_start(ctx); |
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const EC_GROUP *group = EC_KEY_get0_group(pkey); |
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BIGNUM *order = BN_CTX_get(ctx); |
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BIGNUM *halforder = BN_CTX_get(ctx); |
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EC_GROUP_get_order(group, order, ctx); |
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BN_rshift1(halforder, order); |
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if (lowS && BN_cmp(sig->s, halforder) > 0) { |
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// enforce low S values, by negating the value (modulo the order) if above order/2.
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BN_sub(sig->s, order, sig->s); |
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} |
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BN_CTX_end(ctx); |
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BN_CTX_free(ctx); |
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unsigned int nSize = ECDSA_size(pkey); |
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vchSig.resize(nSize); // Make sure it is big enough
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unsigned char *pos = &vchSig[0]; |
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nSize = i2d_ECDSA_SIG(sig, &pos); |
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ECDSA_SIG_free(sig); |
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vchSig.resize(nSize); // Shrink to fit actual size
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return true; |
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} |
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bool CECKey::Verify(const uint256 &hash, const std::vector<unsigned char>& vchSig) { |
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// -1 = error, 0 = bad sig, 1 = good
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if (ECDSA_verify(0, (unsigned char*)&hash, sizeof(hash), &vchSig[0], vchSig.size(), pkey) != 1) |
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return false; |
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return true; |
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} |
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bool CECKey::SignCompact(const uint256 &hash, unsigned char *p64, int &rec) { |
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bool fOk = false; |
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ECDSA_SIG *sig = ECDSA_do_sign((unsigned char*)&hash, sizeof(hash), pkey); |
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if (sig==NULL) |
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return false; |
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memset(p64, 0, 64); |
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int nBitsR = BN_num_bits(sig->r); |
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int nBitsS = BN_num_bits(sig->s); |
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if (nBitsR <= 256 && nBitsS <= 256) { |
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std::vector<unsigned char> pubkey; |
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GetPubKey(pubkey, true); |
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for (int i=0; i<4; i++) { |
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CECKey keyRec; |
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if (ECDSA_SIG_recover_key_GFp(keyRec.pkey, sig, (unsigned char*)&hash, sizeof(hash), i, 1) == 1) { |
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std::vector<unsigned char> pubkeyRec; |
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keyRec.GetPubKey(pubkeyRec, true); |
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if (pubkeyRec == pubkey) { |
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rec = i; |
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fOk = true; |
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break; |
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} |
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} |
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} |
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assert(fOk); |
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BN_bn2bin(sig->r,&p64[32-(nBitsR+7)/8]); |
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BN_bn2bin(sig->s,&p64[64-(nBitsS+7)/8]); |
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} |
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ECDSA_SIG_free(sig); |
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return fOk; |
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} |
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bool CECKey::Recover(const uint256 &hash, const unsigned char *p64, int rec) |
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{ |
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if (rec<0 || rec>=3) |
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return false; |
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ECDSA_SIG *sig = ECDSA_SIG_new(); |
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BN_bin2bn(&p64[0], 32, sig->r); |
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BN_bin2bn(&p64[32], 32, sig->s); |
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bool ret = ECDSA_SIG_recover_key_GFp(pkey, sig, (unsigned char*)&hash, sizeof(hash), rec, 0) == 1; |
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ECDSA_SIG_free(sig); |
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return ret; |
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} |
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bool CECKey::TweakSecret(unsigned char vchSecretOut[32], const unsigned char vchSecretIn[32], const unsigned char vchTweak[32]) |
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{ |
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bool ret = true; |
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BN_CTX *ctx = BN_CTX_new(); |
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BN_CTX_start(ctx); |
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BIGNUM *bnSecret = BN_CTX_get(ctx); |
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BIGNUM *bnTweak = BN_CTX_get(ctx); |
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BIGNUM *bnOrder = BN_CTX_get(ctx); |
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EC_GROUP *group = EC_GROUP_new_by_curve_name(NID_secp256k1); |
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EC_GROUP_get_order(group, bnOrder, ctx); // what a grossly inefficient way to get the (constant) group order...
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BN_bin2bn(vchTweak, 32, bnTweak); |
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if (BN_cmp(bnTweak, bnOrder) >= 0) |
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ret = false; // extremely unlikely
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BN_bin2bn(vchSecretIn, 32, bnSecret); |
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BN_add(bnSecret, bnSecret, bnTweak); |
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BN_nnmod(bnSecret, bnSecret, bnOrder, ctx); |
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if (BN_is_zero(bnSecret)) |
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ret = false; // ridiculously unlikely
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int nBits = BN_num_bits(bnSecret); |
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memset(vchSecretOut, 0, 32); |
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BN_bn2bin(bnSecret, &vchSecretOut[32-(nBits+7)/8]); |
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EC_GROUP_free(group); |
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BN_CTX_end(ctx); |
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BN_CTX_free(ctx); |
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return ret; |
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} |
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bool CECKey::TweakPublic(const unsigned char vchTweak[32]) { |
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bool ret = true; |
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BN_CTX *ctx = BN_CTX_new(); |
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BN_CTX_start(ctx); |
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BIGNUM *bnTweak = BN_CTX_get(ctx); |
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BIGNUM *bnOrder = BN_CTX_get(ctx); |
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BIGNUM *bnOne = BN_CTX_get(ctx); |
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const EC_GROUP *group = EC_KEY_get0_group(pkey); |
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EC_GROUP_get_order(group, bnOrder, ctx); // what a grossly inefficient way to get the (constant) group order...
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BN_bin2bn(vchTweak, 32, bnTweak); |
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if (BN_cmp(bnTweak, bnOrder) >= 0) |
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ret = false; // extremely unlikely
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EC_POINT *point = EC_POINT_dup(EC_KEY_get0_public_key(pkey), group); |
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BN_one(bnOne); |
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EC_POINT_mul(group, point, bnTweak, point, bnOne, ctx); |
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if (EC_POINT_is_at_infinity(group, point)) |
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ret = false; // ridiculously unlikely
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EC_KEY_set_public_key(pkey, point); |
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EC_POINT_free(point); |
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BN_CTX_end(ctx); |
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BN_CTX_free(ctx); |
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return ret; |
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} |
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bool CECKey::SanityCheck() |
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{ |
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EC_KEY *pkey = EC_KEY_new_by_curve_name(NID_secp256k1); |
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if(pkey == NULL) |
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return false; |
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EC_KEY_free(pkey); |
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// TODO Is there more EC functionality that could be missing?
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return true; |
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} |
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@ -0,0 +1,46 @@
@@ -0,0 +1,46 @@
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// Copyright (c) 2009-2014 The Bitcoin developers
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// Distributed under the MIT/X11 software license, see the accompanying
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// file COPYING or http://www.opensource.org/licenses/mit-license.php.
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#ifndef BITCOIN_EC_WRAPPER_H |
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#define BITCOIN_EC_WRAPPER_H |
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#include <cstddef> |
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#include <vector> |
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#include <openssl/ec.h> |
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class uint256; |
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// RAII Wrapper around OpenSSL's EC_KEY
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class CECKey { |
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private: |
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EC_KEY *pkey; |
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public: |
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CECKey(); |
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~CECKey(); |
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void GetSecretBytes(unsigned char vch[32]) const; |
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void SetSecretBytes(const unsigned char vch[32]); |
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int GetPrivKeySize(bool fCompressed); |
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int GetPrivKey(unsigned char* privkey, bool fCompressed); |
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bool SetPrivKey(const unsigned char* privkey, size_t size, bool fSkipCheck=false); |
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void GetPubKey(std::vector<unsigned char>& pubkey, bool fCompressed); |
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bool SetPubKey(const unsigned char* pubkey, size_t size); |
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bool Sign(const uint256 &hash, std::vector<unsigned char>& vchSig, bool lowS); |
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bool Verify(const uint256 &hash, const std::vector<unsigned char>& vchSig); |
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bool SignCompact(const uint256 &hash, unsigned char *p64, int &rec); |
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// reconstruct public key from a compact signature
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// This is only slightly more CPU intensive than just verifying it.
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// If this function succeeds, the recovered public key is guaranteed to be valid
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// (the signature is a valid signature of the given data for that key)
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bool Recover(const uint256 &hash, const unsigned char *p64, int rec); |
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static bool TweakSecret(unsigned char vchSecretOut[32], const unsigned char vchSecretIn[32], const unsigned char vchTweak[32]); |
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bool TweakPublic(const unsigned char vchTweak[32]); |
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static bool SanityCheck(); |
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}; |
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#endif |
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