frost trusted dealer: share generation

This commit adds trusted share generation, as well as share serialization and parsing.
2023-11-23 11:14:41 -07:00
parent 6f47d2eb22
commit 8969cee21c
5 changed files with 241 additions and 0 deletions
--- a/include/secp256k1_frost.h
+++ b/include/secp256k1_frost.h
@@ -17,6 +17,84 @@ extern "C" {
 * (https://crysp.uwaterloo.ca/software/frost/).
 */

+/** Opaque data structures
+ *
+ *  The exact representation of data inside is implementation defined and not
+ *  guaranteed to be portable between different platforms or versions. If you
+ *  need to convert to a format suitable for storage, transmission, or
+ *  comparison, use the corresponding serialization and parsing functions.
+ */
+
+/** Opaque data structure that holds a signer's _secret_ share.
+ *
+ *  Guaranteed to be 36 bytes in size. Serialized and parsed with
+ *  `frost_share_serialize` and `frost_share_parse`.
+ */
+typedef struct {
+    unsigned char data[36];
+} secp256k1_frost_share;
+
+/** Serialize a FROST share
+ *
+ *  Returns: 1 when the share could be serialized, 0 otherwise
+ *  Args:    ctx: a secp256k1 context object
+ *  Out:   out32: pointer to a 32-byte array to store the serialized share
+ *  In:    share: pointer to the share
+ */
+SECP256K1_API int secp256k1_frost_share_serialize(
+    const secp256k1_context *ctx,
+    unsigned char *out32,
+    const secp256k1_frost_share *share
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Parse a FROST share.
+ *
+ *  Returns: 1 when the share could be parsed, 0 otherwise.
+ *  Args:    ctx: a secp256k1 context object
+ *  Out:   share: pointer to a share object
+ *  In:     in32: pointer to the 32-byte share to be parsed
+ */
+SECP256K1_API int secp256k1_frost_share_parse(
+    const secp256k1_context *ctx,
+    secp256k1_frost_share *share,
+    const unsigned char *in32
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Creates key generation shares
+ *
+ *  To generate a key, a trusted dealer generates a share for each other
+ *  participant.
+ *
+ *  Each participant _must_ have a secure channel with the trusted dealer with
+ *  which they can transmit shares to each other.
+ *
+ *  A new seed32 _must_ be used for each key generation session. The trusted
+ *  dealer must NOT REUSE their respective seed32 again for subsequent key
+ *  generation sessions. If a trusted dealer fails to complete this session or
+ *  start a new session to generate a new key, they must NOT REUSE their
+ *  respective seed32 again, but instead generate a new one. It is recommended
+ *  to always choose seed32 uniformly at random to avoid their reuse.
+ *
+ *  Returns: 0 if the arguments are invalid, 1 otherwise
+ *  Args:            ctx: pointer to a context object
+ *  Out:          shares: pointer to the key generation shares
+ *             pubshares: pointer to the public verification shares
+ *                    pk: pointer to the x-only public key
+ *   In:          seed32: a 32-byte seed as explained above
+ *             threshold: the minimum number of signers required to produce a
+ *                        signature
+ *        n_participants: the total number of participants
+ */
+SECP256K1_API int secp256k1_frost_shares_trusted_gen(
+    const secp256k1_context *ctx,
+    secp256k1_frost_share *shares,
+    secp256k1_pubkey *pubshares,
+    secp256k1_xonly_pubkey *pk,
+    const unsigned char *seed32,
+    size_t threshold,
+    size_t n_participants
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(5);
+
 #ifdef __cplusplus
 }
 #endif