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Add support for multiplicative tweaking

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This commit is contained in:
Pieter Wuille 2013-07-14 17:43:13 +02:00
parent b0be6aba91
commit 86d3cce2a9
2 changed files with 61 additions and 4 deletions
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6
include/secp256k1.h
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@ -108,8 +108,10 @@ int secp256k1_ecdsa_privkey_export(const unsigned char *seckey,
int secp256k1_ecdsa_privkey_import(unsigned char *seckey, int secp256k1_ecdsa_privkey_import(unsigned char *seckey,
const unsigned char *privkey, int privkeylen); const unsigned char *privkey, int privkeylen);
int secp256k1_ecdsa_privkey_tweak(unsigned char *seckey, const unsigned char *tweak); int secp256k1_ecdsa_privkey_tweak_add(unsigned char *seckey, const unsigned char *tweak);
int secp256k1_ecdsa_pubkey_tweak(unsigned char *pubkey, int pubkeylen, const unsigned char *tweak); int secp256k1_ecdsa_pubkey_tweak_add(unsigned char *pubkey, int pubkeylen, const unsigned char *tweak);
int secp256k1_ecdsa_privkey_tweak_mul(unsigned char *seckey, const unsigned char *tweak);
int secp256k1_ecdsa_pubkey_tweak_mul(unsigned char *pubkey, int pubkeylen, const unsigned char *tweak);
#ifdef __cplusplus #ifdef __cplusplus
} }

59
src/secp256k1.c
View File

@ -146,7 +146,7 @@ int secp256k1_ecdsa_pubkey_decompress(unsigned char *pubkey, int *pubkeylen) {
return 1; return 1;
} }
int secp256k1_ecdsa_privkey_tweak(unsigned char *seckey, const unsigned char *tweak) { int secp256k1_ecdsa_privkey_tweak_add(unsigned char *seckey, const unsigned char *tweak) {
int ret = 1; int ret = 1;
secp256k1_num_t term; secp256k1_num_t term;
secp256k1_num_init(&term); secp256k1_num_init(&term);
@ -169,7 +169,7 @@ int secp256k1_ecdsa_privkey_tweak(unsigned char *seckey, const unsigned char *tw
return ret; return ret;
} }
int secp256k1_ecdsa_pubkey_tweak(unsigned char *pubkey, int pubkeylen, const unsigned char *tweak) { int secp256k1_ecdsa_pubkey_tweak_add(unsigned char *pubkey, int pubkeylen, const unsigned char *tweak) {
int ret = 1; int ret = 1;
secp256k1_num_t term; secp256k1_num_t term;
secp256k1_num_init(&term); secp256k1_num_init(&term);
@ -185,6 +185,61 @@ int secp256k1_ecdsa_pubkey_tweak(unsigned char *pubkey, int pubkeylen, const uns
secp256k1_gej_t pt; secp256k1_gej_t pt;
secp256k1_ecmult_gen(&pt, &term); secp256k1_ecmult_gen(&pt, &term);
secp256k1_gej_add_ge(&pt, &pt, &p); secp256k1_gej_add_ge(&pt, &pt, &p);
if (secp256k1_gej_is_infinity(&pt))
ret = 0;
secp256k1_ge_set_gej(&p, &pt);
int oldlen = pubkeylen;
secp256k1_ecdsa_pubkey_serialize(&p, pubkey, &pubkeylen, oldlen <= 33);
assert(pubkeylen == oldlen);
}
secp256k1_num_free(&term);
return ret;
}
int secp256k1_ecdsa_privkey_tweak_mul(unsigned char *seckey, const unsigned char *tweak) {
int ret = 1;
secp256k1_num_t term;
secp256k1_num_init(&term);
secp256k1_num_set_bin(&term, tweak, 32);
if (secp256k1_num_is_zero(&term))
ret = 0;
if (secp256k1_num_cmp(&term, &secp256k1_ge_consts->order) >= 0)
ret = 0;
secp256k1_num_t sec;
secp256k1_num_init(&sec);
if (ret) {
secp256k1_num_set_bin(&term, seckey, 32);
secp256k1_num_mod_mul(&sec, &sec, &term, &secp256k1_ge_consts->order);
}
if (ret)
secp256k1_num_get_bin(seckey, 32, &sec);
secp256k1_num_free(&sec);
secp256k1_num_free(&term);
return ret;
}
int secp256k1_ecdsa_pubkey_tweak_mul(unsigned char *pubkey, int pubkeylen, const unsigned char *tweak) {
int ret = 1;
secp256k1_num_t term;
secp256k1_num_init(&term);
secp256k1_num_set_bin(&term, tweak, 32);
if (secp256k1_num_is_zero(&term))
ret = 0;
if (secp256k1_num_cmp(&term, &secp256k1_ge_consts->order) >= 0)
ret = 0;
secp256k1_ge_t p;
if (ret) {
if (!secp256k1_ecdsa_pubkey_parse(&p, pubkey, pubkeylen))
ret = 0;
}
if (ret) {
secp256k1_num_t zero;
secp256k1_num_init(&zero);
secp256k1_num_set_int(&zero, 0);
secp256k1_gej_t pt;
secp256k1_gej_set_ge(&pt, &p);
secp256k1_ecmult(&pt, &pt, &term, &zero);
secp256k1_num_free(&zero);
secp256k1_ge_set_gej(&p, &pt); secp256k1_ge_set_gej(&p, &pt);
int oldlen = pubkeylen; int oldlen = pubkeylen;
secp256k1_ecdsa_pubkey_serialize(&p, pubkey, &pubkeylen, oldlen <= 33); secp256k1_ecdsa_pubkey_serialize(&p, pubkey, &pubkeylen, oldlen <= 33);