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musig: add pubkey_get to obtain a full pubkey from a keyagg_cache

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This commit is contained in:
Jonas Nick 2021-10-25 21:57:30 +00:00
parent 21e2d65b79
commit c519b46879
3 changed files with 42 additions and 0 deletions
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18
include/secp256k1_musig.h
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@ -223,6 +223,24 @@ SECP256K1_API int secp256k1_musig_pubkey_agg(
size_t n_pubkeys
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(5);
/** Obtain the aggregate public key from a keyagg_cache.
*
* This is only useful if you need the non-xonly public key, in particular for
* ordinary (non-xonly) tweaking or batch-verifying multiple key aggregations
* (not implemented).
*
* Returns: 0 if the arguments are invalid, 1 otherwise
* Args: ctx: pointer to a context object
* Out: agg_pk: the MuSig-aggregated public key.
* In: keyagg_cache: pointer to a `musig_keyagg_cache` struct initialized by
* `musig_pubkey_agg`
*/
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_musig_pubkey_get(
const secp256k1_context* ctx,
secp256k1_pubkey *agg_pk,
secp256k1_musig_keyagg_cache *keyagg_cache
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
/** Tweak an x-only public key in a given keyagg_cache by adding
* the generator multiplied with `tweak32` to it.
*

14
src/modules/musig/keyagg_impl.h
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@ -244,6 +244,20 @@ int secp256k1_musig_pubkey_agg(const secp256k1_context* ctx, secp256k1_scratch_s
return 1;
}
int secp256k1_musig_pubkey_get(const secp256k1_context* ctx, secp256k1_pubkey *agg_pk, secp256k1_musig_keyagg_cache *keyagg_cache) {
secp256k1_keyagg_cache_internal cache_i;
VERIFY_CHECK(ctx != NULL);
ARG_CHECK(agg_pk != NULL);
memset(agg_pk, 0, sizeof(*agg_pk));
ARG_CHECK(keyagg_cache != NULL);
if(!secp256k1_keyagg_cache_load(ctx, &cache_i, keyagg_cache)) {
return 0;
}
secp256k1_pubkey_save(agg_pk, &cache_i.pk);
return 1;
}
int secp256k1_musig_pubkey_tweak_add(const secp256k1_context* ctx, secp256k1_pubkey *output_pubkey, secp256k1_musig_keyagg_cache *keyagg_cache, const unsigned char *tweak32) {
secp256k1_keyagg_cache_internal cache_i;
int overflow = 0;

10
src/modules/musig/tests_impl.h
View File

@ -140,6 +140,7 @@ void musig_api_tests(secp256k1_scratch_space *scratch) {
unsigned char aggnonce_ser[66];
unsigned char msg[32];
secp256k1_xonly_pubkey agg_pk;
secp256k1_pubkey full_agg_pk;
secp256k1_musig_keyagg_cache keyagg_cache;
secp256k1_musig_keyagg_cache invalid_keyagg_cache;
secp256k1_musig_session session;
@ -243,6 +244,15 @@ void musig_api_tests(secp256k1_scratch_space *scratch) {
CHECK(secp256k1_musig_pubkey_agg(sign, scratch, &agg_pk, &keyagg_cache, pk_ptr, 2) == 1);
CHECK(secp256k1_musig_pubkey_agg(vrfy, scratch, &agg_pk, &keyagg_cache, pk_ptr, 2) == 1);
/* pubkey_get */
ecount = 0;
CHECK(secp256k1_musig_pubkey_get(none, &full_agg_pk, &keyagg_cache) == 1);
CHECK(secp256k1_musig_pubkey_get(none, NULL, &keyagg_cache) == 0);
CHECK(ecount == 1);
CHECK(secp256k1_musig_pubkey_get(none, &full_agg_pk, NULL) == 0);
CHECK(ecount == 2);
CHECK(secp256k1_memcmp_var(&full_agg_pk, zeros68, sizeof(full_agg_pk)) == 0);
/** Tweaking **/
ecount = 0;
{