diff --git a/src/secp256k1/include/secp256k1.h b/src/secp256k1/include/secp256k1.h index f268e309d0..7e7a6427da 100644 --- a/src/secp256k1/include/secp256k1.h +++ b/src/secp256k1/include/secp256k1.h @@ -485,6 +485,29 @@ SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_create( const unsigned char *seckey ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); +/** Negates a private key in place. + * + * Returns: 1 always + * Args: ctx: pointer to a context object + * In/Out: pubkey: pointer to the public key to be negated (cannot be NULL) + */ +SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_negate( + const secp256k1_context* ctx, + unsigned char *seckey +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2); + +/** Negates a public key in place. + * + * Returns: 1 always + * Args: ctx: pointer to a context object + * In/Out: pubkey: pointer to the public key to be negated (cannot be NULL) + */ +SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_negate( + const secp256k1_context* ctx, + secp256k1_pubkey *pubkey +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2); + + /** Tweak a private key by adding tweak to it. * Returns: 0 if the tweak was out of range (chance of around 1 in 2^128 for * uniformly random 32-byte arrays, or if the resulting private key diff --git a/src/secp256k1/src/secp256k1.c b/src/secp256k1/src/secp256k1.c index fa076ca6dc..efb5bcbfa4 100755 --- a/src/secp256k1/src/secp256k1.c +++ b/src/secp256k1/src/secp256k1.c @@ -445,6 +445,30 @@ int secp256k1_ec_pubkey_create(const secp256k1_context* ctx, secp256k1_pubkey *p return ret; } +int secp256k1_ec_privkey_negate(const secp256k1_context* ctx, unsigned char *seckey) { + secp256k1_scalar sec; + VERIFY_CHECK(ctx != NULL); + ARG_CHECK(seckey != NULL); + + secp256k1_scalar_set_b32(&sec, seckey, NULL); + secp256k1_scalar_negate(&sec, &sec); + secp256k1_scalar_get_b32(seckey, &sec); + + return 1; +} + +int secp256k1_ec_pubkey_negate(const secp256k1_context* ctx, secp256k1_pubkey *pubkey) { + int ret = 0; + secp256k1_ge p; + VERIFY_CHECK(ctx != NULL); + ARG_CHECK(pubkey != NULL); + + ret = secp256k1_pubkey_load(ctx, &p, pubkey); + secp256k1_ge_neg(&p, &p); + secp256k1_pubkey_save(pubkey, &p); + return ret; +} + int secp256k1_ec_privkey_tweak_add(const secp256k1_context* ctx, unsigned char *seckey, const unsigned char *tweak) { secp256k1_scalar term; secp256k1_scalar sec; diff --git a/src/secp256k1/src/tests.c b/src/secp256k1/src/tests.c index e927f087d0..353ce0f357 100644 --- a/src/secp256k1/src/tests.c +++ b/src/secp256k1/src/tests.c @@ -10,6 +10,7 @@ #include #include +#include #include @@ -3482,6 +3483,7 @@ void test_ecdsa_end_to_end(void) { unsigned char pubkeyc[65]; size_t pubkeyclen = 65; secp256k1_pubkey pubkey; + secp256k1_pubkey pubkey_tmp; unsigned char seckey[300]; size_t seckeylen = 300; @@ -3503,6 +3505,13 @@ void test_ecdsa_end_to_end(void) { memset(&pubkey, 0, sizeof(pubkey)); CHECK(secp256k1_ec_pubkey_parse(ctx, &pubkey, pubkeyc, pubkeyclen) == 1); + /* Verify negation changes the key and changes it back */ + memcpy(&pubkey_tmp, &pubkey, sizeof(pubkey)); + CHECK(secp256k1_ec_pubkey_negate(ctx, &pubkey_tmp) == 1); + CHECK(memcmp(&pubkey_tmp, &pubkey, sizeof(pubkey)) != 0); + CHECK(secp256k1_ec_pubkey_negate(ctx, &pubkey_tmp) == 1); + CHECK(memcmp(&pubkey_tmp, &pubkey, sizeof(pubkey)) == 0); + /* Verify private key import and export. */ CHECK(ec_privkey_export_der(ctx, seckey, &seckeylen, privkey, secp256k1_rand_bits(1) == 1)); CHECK(ec_privkey_import_der(ctx, privkey2, seckey, seckeylen) == 1);