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Merge #845: Extract the secret key from a keypair

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33cb3c2b1f Add secret key extraction from keypair to constant time tests (Elichai Turkel)
36d9dc1e8e Add seckey extraction from keypair to the extrakeys tests (Elichai Turkel)
fc96aa73f5 Add a function to extract the secretkey from a keypair (Elichai Turkel)

Pull request description:

  With schnorrsig if you need to tweak the secret key (for BIP32) you must use the keypair API to get compatible secret/public keys which you do by calling `secp256k1_keypair_xonly_tweak_add()`, but after that there's no currently a way to extract the secret key back for storage.
  so I added a `secp256k1_keypair_seckey` function to extract the key

ACKs for top commit:
  jonasnick:
    ACK 33cb3c2b1f
  real-or-random:
    ACK 33cb3c2b1f code inspection, tests pass

Tree-SHA512: 11212db38c8b87a87e2dc35c4d6993716867b45215b94b20522b1b3164ca63d4c6bf5192a6bff0e9267b333779cc8164844c56669a94e9be72df9ef025ffcfd4
This commit is contained in:
Tim Ruffing
2021-01-12 10:54:51 +01:00
parent 8c727b9087 33cb3c2b1f
commit 328aaef22a
4 changed files with 55 additions and 1 deletions
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10
src/modules/extrakeys/main_impl.h
View File

@@ -186,6 +186,16 @@ int secp256k1_keypair_create(const secp256k1_context* ctx, secp256k1_keypair *ke
return ret;
}
int secp256k1_keypair_sec(const secp256k1_context* ctx, unsigned char *seckey, const secp256k1_keypair *keypair) {
VERIFY_CHECK(ctx != NULL);
ARG_CHECK(seckey != NULL);
memset(seckey, 0, 32);
ARG_CHECK(keypair != NULL);
memcpy(seckey, &keypair->data[0], 32);
return 1;
}
int secp256k1_keypair_pub(const secp256k1_context* ctx, secp256k1_pubkey *pubkey, const secp256k1_keypair *keypair) {
VERIFY_CHECK(ctx != NULL);
ARG_CHECK(pubkey != NULL);

27
src/modules/extrakeys/tests_impl.h
View File

@@ -311,6 +311,7 @@ void test_xonly_pubkey_tweak_recursive(void) {
void test_keypair(void) {
unsigned char sk[32];
unsigned char sk_tmp[32];
unsigned char zeros96[96] = { 0 };
unsigned char overflows[32];
secp256k1_keypair keypair;
@@ -396,6 +397,28 @@ void test_keypair(void) {
CHECK(secp256k1_memcmp_var(&xonly_pk, &xonly_pk_tmp, sizeof(pk)) == 0);
CHECK(pk_parity == pk_parity_tmp);
/* Test keypair_seckey */
ecount = 0;
secp256k1_testrand256(sk);
CHECK(secp256k1_keypair_create(ctx, &keypair, sk) == 1);
CHECK(secp256k1_keypair_sec(none, sk_tmp, &keypair) == 1);
CHECK(secp256k1_keypair_sec(none, NULL, &keypair) == 0);
CHECK(ecount == 1);
CHECK(secp256k1_keypair_sec(none, sk_tmp, NULL) == 0);
CHECK(ecount == 2);
CHECK(secp256k1_memcmp_var(zeros96, sk_tmp, sizeof(sk_tmp)) == 0);
/* keypair returns the same seckey it got */
CHECK(secp256k1_keypair_create(sign, &keypair, sk) == 1);
CHECK(secp256k1_keypair_sec(none, sk_tmp, &keypair) == 1);
CHECK(secp256k1_memcmp_var(sk, sk_tmp, sizeof(sk_tmp)) == 0);
/* Using an invalid keypair is fine for keypair_seckey */
memset(&keypair, 0, sizeof(keypair));
CHECK(secp256k1_keypair_sec(none, sk_tmp, &keypair) == 1);
CHECK(secp256k1_memcmp_var(zeros96, sk_tmp, sizeof(sk_tmp)) == 0);
secp256k1_context_destroy(none);
secp256k1_context_destroy(sign);
secp256k1_context_destroy(verify);
@@ -484,6 +507,7 @@ void test_keypair_add(void) {
secp256k1_pubkey output_pk_xy;
secp256k1_pubkey output_pk_expected;
unsigned char pk32[32];
unsigned char sk32[32];
int pk_parity;
secp256k1_testrand256(tweak);
@@ -501,7 +525,8 @@ void test_keypair_add(void) {
CHECK(secp256k1_memcmp_var(&output_pk_xy, &output_pk_expected, sizeof(output_pk_xy)) == 0);
/* Check that the secret key in the keypair is tweaked correctly */
CHECK(secp256k1_ec_pubkey_create(ctx, &output_pk_expected, &keypair.data[0]) == 1);
CHECK(secp256k1_keypair_sec(none, sk32, &keypair) == 1);
CHECK(secp256k1_ec_pubkey_create(ctx, &output_pk_expected, sk32) == 1);
CHECK(secp256k1_memcmp_var(&output_pk_xy, &output_pk_expected, sizeof(output_pk_xy)) == 0);
}
secp256k1_context_destroy(none);