From 8e48aa60dc9ab9d9b4b417ed520372d4e35b5a31 Mon Sep 17 00:00:00 2001 From: Andrew Poelstra Date: Thu, 28 Jul 2016 16:05:40 +0000 Subject: [PATCH] Add `secp256k1_ec_pubkey_negate` and `secp256k1_ec_privkey_negate` --- include/secp256k1.h | 22 ++++++++++++++++++++++ src/secp256k1.c | 27 +++++++++++++++++++++++++++ src/tests.c | 26 +++++++++++++++++++++++--- 3 files changed, 72 insertions(+), 3 deletions(-) diff --git a/include/secp256k1.h b/include/secp256k1.h index 7145dbcc54a79..18a72545a1b12 100644 --- a/include/secp256k1.h +++ b/include/secp256k1.h @@ -491,6 +491,28 @@ 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.c b/src/secp256k1.c index 7973d60c36a81..8ca258f7f8ac6 100644 --- a/src/secp256k1.c +++ b/src/secp256k1.c @@ -424,6 +424,33 @@ 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); + memset(pubkey, 0, sizeof(*pubkey)); + if (ret) { + 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/tests.c b/src/tests.c index b32cb90813718..21ce055d35dc8 100644 --- a/src/tests.c +++ b/src/tests.c @@ -10,6 +10,7 @@ #include #include +#include #include @@ -135,6 +136,7 @@ void random_scalar_order(secp256k1_scalar *num) { void run_context_tests(void) { secp256k1_pubkey pubkey; + secp256k1_pubkey zero_pubkey; secp256k1_ecdsa_signature sig; unsigned char ctmp[32]; int32_t ecount; @@ -149,6 +151,8 @@ void run_context_tests(void) { secp256k1_scalar msg, key, nonce; secp256k1_scalar sigr, sigs; + memset(&zero_pubkey, 0, sizeof(zero_pubkey)); + ecount = 0; ecount2 = 10; secp256k1_context_set_illegal_callback(vrfy, counting_illegal_callback_fn, &ecount); @@ -201,12 +205,20 @@ void run_context_tests(void) { CHECK(ecount == 2); CHECK(secp256k1_ec_pubkey_tweak_mul(sign, &pubkey, ctmp) == 0); CHECK(ecount2 == 13); - CHECK(secp256k1_ec_pubkey_tweak_mul(vrfy, &pubkey, ctmp) == 1); + CHECK(secp256k1_ec_pubkey_negate(vrfy, &pubkey) == 1); CHECK(ecount == 2); - CHECK(secp256k1_context_randomize(vrfy, ctmp) == 0); + CHECK(secp256k1_ec_pubkey_negate(sign, &pubkey) == 1); + CHECK(ecount == 2); + CHECK(secp256k1_ec_pubkey_negate(sign, NULL) == 0); + CHECK(ecount2 == 14); + CHECK(secp256k1_ec_pubkey_negate(vrfy, &zero_pubkey) == 0); + CHECK(ecount == 3); + CHECK(secp256k1_ec_pubkey_tweak_mul(vrfy, &pubkey, ctmp) == 1); CHECK(ecount == 3); + CHECK(secp256k1_context_randomize(vrfy, ctmp) == 0); + CHECK(ecount == 4); CHECK(secp256k1_context_randomize(sign, NULL) == 1); - CHECK(ecount2 == 13); + CHECK(ecount2 == 14); secp256k1_context_set_illegal_callback(vrfy, NULL, NULL); secp256k1_context_set_illegal_callback(sign, NULL, NULL); @@ -3436,6 +3448,7 @@ 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; @@ -3457,6 +3470,13 @@ 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);