118 lines
3.6 KiB
C++
118 lines
3.6 KiB
C++
// Copyright (c) 2009-2012 The Bitcoin developers
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// Distributed under the MIT/X11 software license, see the accompanying
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// file license.txt or http://www.opensource.org/licenses/mit-license.php.
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#include <openssl/ec.h>
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#include <openssl/ecdsa.h>
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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 nonzero, 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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