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build: wire the frost_enrollment module into both build systems Second of six commits adding the frost_enrollment module. This one is scaffolding only: the five entry points are stubs that validate their pointer arguments, zero their outputs and return 0. What is being verified here is that the module configures, compiles, links, exports its symbols and registers its test module in both build systems -- so that the next commit changes nothing but arithmetic. Ordering is the one thing in this commit that can go silently wrong, and it goes wrong in opposite directions in the two build systems: - configure.ac executes its `if` blocks in file order, and enable_module_frost defaults to no (configure.ac:243). A block placed after the frost block at :601 that sets enable_module_frost=yes flips the variable too late: AM_CONDITIONAL goes true, so the header is installed and the Makefile fragment is pulled in, but -DENABLE_MODULE_FROST=1 is never appended, so src/secp256k1.c never includes frost's implementation and every secp256k1_frost_* symbol fails to link. The new block therefore goes ahead of both the frost block and prefractal's, which documents the same trap. - src/CMakeLists.txt processes dependents FIRST, so the same block goes above the FROST block there, beside prefractal's. Verified rather than assumed: configuring with ONLY --enable-module-frost-enrollment emits -DENABLE_MODULE_FROST=1 alongside -DENABLE_MODULE_FROST_ENROLLMENT=1, and the CMake summary prints "frost ON" for the same configuration -- the latter is what the PARENT_SCOPE lift buys, since the summary runs after add_subdirectory(src) and would otherwise report a module it is compiling in as OFF. The dependency guard is prefractal's implies-frost idiom, copied verbatim along with its reasoning. frost is default-OFF, so the `test x"$enable_module_frost" = x"no"` / `DEFINED X AND NOT X` guard every other module uses -- which reads as "the user disabled it explicitly" for a default-ON dependency -- is true by default here and cannot tell an explicit --disable-module-frost from the default once both are in the cache. Enabling frost-enrollment simply implies frost, with no error. The one frost-module change in the whole series is in this commit: src/modules/frost/session.h gains a declaration for secp256k1_frost_sort_ids, which is defined at session_impl.h:517 and declared nowhere. The params hash needs it to canonicalize identifier order. Prefractal reaches frost's statics through translation-unit ordering alone; rather than inherit reuse-by-link-order, this declares the function where keygen.h:48 already declares derive_pubshare_at, so the reuse goes through an interface. No behavior change: it is a declaration for an existing static definition in the same TU. CI wiring is two files, and skipping either half fails quietly: - ci/ci.sh gets FROST_ENROLLMENT in the reproduction header's variable list and --enable-module-frost-enrollment="$FROST_ENROLLMENT" after the prefractal line. - .github/workflows/ci.yml gets FROST_ENROLLMENT at every PREFRACTAL site: the global default, 11 inline matrix entries and 10 job-level env blocks. Without the default, ci.sh runs under set -eux with an empty $FROST_ENROLLMENT, passes --enable-module-frost-enrollment="", `test x"" = x"yes"` is false, and the module is off in all of CI while ci.sh visibly has the plumbing. Verified programmatically over the parsed workflow: across the 106 effective job contexts, PREFRACTAL and FROST_ENROLLMENT now agree in every single one (45 set to yes, no mismatches), no context sets FROST_ENROLLMENT without FROST or without EXPERIMENTAL, and no context leaves it undefined. ci.sh passes sh -n. The stub test is not a placeholder that has to be deleted later: every entry point must reject an empty helper set and leave its output zeroed, which is true of the stubs and stays true of the finished implementation, so it doubles as the check that all five symbols are reachable from the test binary. Verification. Autotools: ./autogen.sh, then a frost-enrollment-only configure and a full configure with frost, chilldkg, iceberg, prefractal and frost-enrollment all on -- both build with zero warnings under the project's -Werror-grade flag set, ./tests and ./exhaustive_tests exit 0, and `./tests -l` lists the frost_enrollment module. CMake: configure with -DSECP256K1_EXPERIMENTAL=ON -DSECP256K1_ENABLE_MODULE_FROST_ENROLLMENT=ON builds clean and ctest passes 391 tests. nm shows the five new symbols exported from libsecp256k1.so; tools/symbol-check.py could not be run here because python3-lief is not installed in this environment, but all five carry the required secp256k1_ prefix. make dist succeeds and the tarball carries src/modules/frost_enrollment/frost_enrollment.md alongside the other module documents. One unrelated observation from this build: a stale src/ctime_tests-ctime_tests.o left over from an earlier configure with a different module set will fail to link, because automake does not track CPPFLAGS changes across reconfigures. make clean between configurations with different module sets, not a fault in this change. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-09-04 03:53:03 +02:00
/***********************************************************************
* Distributed under the MIT software license, see the accompanying *
* file COPYING or https://www.opensource.org/licenses/mit-license.php.*
***********************************************************************/
#ifndef SECP256K1_MODULE_FROST_ENROLLMENT_TESTS_IMPL_H
#define SECP256K1_MODULE_FROST_ENROLLMENT_TESTS_IMPL_H
#include "../../../include/secp256k1_frost_enrollment.h"
frost_enrollment: implement the three rounds Third of six commits. Replaces the Phase 1 stubs with the real arithmetic, adds a smoke test that a 2-of-3 group really does grow into a working 2-of-4 one, and wires the entry points into ctime_tests. The Lagrange machinery is frost's, called in place. pubshare_derive is a skin over secp256k1_frost_derive_pubshare_at (src/modules/frost/keygen_impl.h:150) evaluated at identifier new_id, and the id canonicalization is secp256k1_frost_sort_ids, reached through the declaration the previous commit added. The one piece frost could not supply is the scalar Lagrange coefficient at an arbitrary point. frost's secp256k1_frost_derive_interpolating_value evaluates at x-coordinate 0, which is what reconstructing the group secret needs; enrollment needs the basis polynomial at the TARGET x-coordinate. secp256k1_frost_enrollment_lagrange_at is that, and it is deliberately the same product derive_pubshare_at applies to each pubshare, in the same identifier space -- so the scalar path and the point path agree by construction rather than by coincidence. Working in identifier space is what makes the id-to-x-coordinate +1 cancel: an x-coordinate difference x_j - x_i is the identifier difference id_j - id_i. Round 1.1 computes v = lambda * secshare and splits it. Every share but the one kept locally is masking randomness derived as Scalar.from_bytes_wrapping( TH("FROST enrollment/share_split", rand32 || params_hash32 || ser32(my_id) || ser32(recipient_id))) with rand32 = TH(same tag, session_secrand32) XOR secshare32; the kept share absorbs the remainder so the set sums to v. Three details: - The reduction wraps rather than rejects, chilldkg's from_bytes_wrapping (src/modules/chilldkg/util_impl.h:394). A 256-bit hash mod the group order is about 2^-128 from uniform; rejection sampling would buy that back in exchange for a variable-time loop. - Masking with the secret share is the secp256k1_frost_nonce_gen pattern (session_impl.h:340), so a broken RNG alone does not reveal the split. - The derivation is indexed by the recipient's IDENTIFIER, not by its position in the caller's ids array. The plan called for a counter; identifiers are unique, so they are one, and using them makes the split independent of the order a caller lists the helper set in. What the binding buys is DOMAIN SEPARATION only: params_hash32 carries the group key and the whole parameter tuple, so two runs sharing a seed but differing in either cannot produce the same deltas. It cannot detect a disagreement between helpers, because nothing cross-checks per-helper private randomness. That is the params hash's job. session_secrand32 is wiped whether the call succeeds or fails, so a caller cannot retry a failed run on the same randomness. Round 1.2 recomputes its own params hash from the group key and the tuple, compares every received hash against it, then sums. The slot at the caller's own position in received_params_hashes32 is skipped, while the same position in all_shares32 is read -- the asymmetry the header documents, and the thing that makes this a recomputation rather than a string comparison. The mode and bounds are re-validated here rather than trusted from the round 1.1 call site, since the full tuple is present. An out-of-range share is reported through mismatch_id the way secp256k1_frost_partial_sig_agg reports an unparseable partial signature. Round 2 compares the params hash against its own recomputation over the authenticated group key, sums, rejects a zero share, and checks secshare*G against the expected public share. Three deviations from the plan, all to match what the tree already does: - Value ranges return 0; only pointers get ARG_CHECK. The plan called for an ARG_CHECK on the n_ids bound, but the frost module's split is the one used here (secp256k1_frost_trusted_dealer_keygen, keygen_impl.h:227), and the header already documents these as return-0 conditions. The bound is still enforced in production builds -- params_are_valid requires 2 <= threshold <= n_ids <= n_participants <= 128 -- so it does not ride on the VERIFY_CHECK inside secp256k1_frost_sort_ids, which is what the plan was guarding against. - The public-share check declassifies the derived point and compares with secp256k1_ge_eq_var, rather than comparing 33 serialized bytes in constant time. There is no constant-time memcmp in this tree, and secshare*G is a public key: secp256k1_frost_sign declassifies exactly this quantity before exactly this comparison (src/modules/frost/session_impl.h:770, :789). Inventing a primitive to avoid following that precedent would be the worse trade. - params_hash's public entry point delegates to the same internal routine every gate uses, so the encoding has exactly one implementation to keep in step with the vectors. One real bug found by the tooling rather than by reading. Accumulators were initialized with secp256k1_scalar_clear, and secp256k1_memclear_explicit marks its target UNDEFINED in VERIFY builds (src/util.h:295) precisely so that reading cleared memory is caught. It was: valgrind reported 143752 errors in share_agg's summation loop. Accumulators now start at secp256k1_scalar_set_int(x, 0); scalar_clear is used only where it means "done with this secret". Worth stating plainly because the failure mode is invisible in a production build, where memclear_explicit only zeroes. ctime_tests gains a 2-of-3-enrolls-a-fourth block covering all three rounds, following prefractal's b66c757b. The threshold key, the secret shares, the session randomness and every delta and sigma on the wire are marked secret; the identifiers, public shares, group key, parameters hashes and derived public share are not. Under valgrind: 0 errors from 0 contexts, so no branch or memory access in the new code depends on secret data. Verification: ./tests, ./noverify_tests and ./exhaustive_tests exit 0; the frost_enrollment module runs clean under valgrind (0 errors); a separate CPPFLAGS='-DVERIFY' build compiles without warnings and passes; the module builds warning-free alongside frost, chilldkg, iceberg and prefractal. The smoke test is the substantive check: after a 2-of-3 group enrolls participant 3, every pair {i, 3} for i in 0..2 reconstructs the original threshold secret and matches the threshold public key, and the untouched pair {0, 1} still does too. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-09-04 04:06:59 +02:00
/* Everything one enrollment run needs, so a test can set one up in a line and
* then poke at individual pieces. */
typedef struct {
size_t n, t, u;
uint32_t new_id;
unsigned char thresh_sk[32];
unsigned char secshares[SECP256K1_FROST_MAX_PARTICIPANTS][32];
secp256k1_pubkey pubshares[SECP256K1_FROST_MAX_PARTICIPANTS];
secp256k1_pubkey thresh_pk;
uint32_t ids[SECP256K1_FROST_MAX_PARTICIPANTS];
/* shares[i][j] is what helper ids[i] produced for helper ids[j]. */
unsigned char shares[SECP256K1_FROST_MAX_PARTICIPANTS][SECP256K1_FROST_MAX_PARTICIPANTS * 32];
unsigned char params_hashes[SECP256K1_FROST_MAX_PARTICIPANTS][32];
unsigned char sigmas[SECP256K1_FROST_MAX_PARTICIPANTS * 32];
secp256k1_pubkey new_pubshare;
unsigned char new_secshare[32];
} frost_enrollment_test_run;
/* Deals a fresh (t, n) group and fills in the helper set: the first u
* identifiers that are not new_id, in ascending order. */
static void frost_enrollment_test_deal(frost_enrollment_test_run *r, size_t n, size_t t, size_t u, uint32_t new_id) {
size_t i, k;
r->n = n;
r->t = t;
r->u = u;
r->new_id = new_id;
testrand256(r->thresh_sk);
CHECK(secp256k1_frost_trusted_dealer_keygen(CTX, r->secshares[0], &r->thresh_pk, r->pubshares, n, (uint32_t)t, r->thresh_sk) == 1);
k = 0;
for (i = 0; i < n && k < u; i++) {
if ((uint32_t)i == new_id) {
continue;
}
r->ids[k] = (uint32_t)i;
k++;
}
CHECK(k == u);
}
/* Runs round 1.1 for every helper. */
static void frost_enrollment_test_round1_gen(frost_enrollment_test_run *r) {
size_t i;
for (i = 0; i < r->u; i++) {
unsigned char secrand[32];
testrand256(secrand);
CHECK(secp256k1_frost_enrollment_shares_gen(CTX, r->shares[i], r->params_hashes[i], secrand, r->secshares[r->ids[i]], &r->thresh_pk, r->ids, r->u, r->ids[i], r->new_id, r->n, (uint32_t)r->t) == 1);
CHECK(secp256k1_is_zero_array(secrand, sizeof(secrand)));
}
}
/* Runs round 1.2 for every helper, transposing the round 1.1 outputs on the
* way: helper j aggregates entry j of every helper's share buffer. */
static void frost_enrollment_test_round1_agg(frost_enrollment_test_run *r) {
size_t i, j;
for (j = 0; j < r->u; j++) {
unsigned char all_shares[SECP256K1_FROST_MAX_PARTICIPANTS * 32];
unsigned char received[SECP256K1_FROST_MAX_PARTICIPANTS * 32];
uint32_t mismatch_id = 0;
memset(received, 0, r->u * 32);
for (i = 0; i < r->u; i++) {
memcpy(&all_shares[32 * i], &r->shares[i][32 * j], 32);
if (i != j) {
memcpy(&received[32 * i], r->params_hashes[i], 32);
}
}
CHECK(secp256k1_frost_enrollment_share_agg(CTX, &r->sigmas[32 * j], &mismatch_id, all_shares, received, &r->thresh_pk, r->ids, r->u, r->ids[j], r->new_id, r->n, (uint32_t)r->t) == 1);
CHECK(mismatch_id == UINT32_MAX);
}
}
/* Runs round 2, with both optional checks enabled. */
static void frost_enrollment_test_round2(frost_enrollment_test_run *r) {
CHECK(secp256k1_frost_enrollment_pubshare_derive(CTX, &r->new_pubshare, r->pubshares, r->ids, r->u, r->new_id, r->n, (uint32_t)r->t) == 1);
CHECK(secp256k1_frost_enrollment_secshare_gen(CTX, r->new_secshare, r->sigmas, &r->thresh_pk, r->ids, r->u, r->new_id, r->n, (uint32_t)r->t, r->params_hashes[0], &r->new_pubshare) == 1);
}
static void frost_enrollment_test_full_run(frost_enrollment_test_run *r, size_t n, size_t t, size_t u, uint32_t new_id) {
frost_enrollment_test_deal(r, n, t, u, new_id);
frost_enrollment_test_round1_gen(r);
frost_enrollment_test_round1_agg(r);
frost_enrollment_test_round2(r);
}
/* Reconstructs the threshold secret from the shares of the given identifiers
* and checks it against the threshold public key. shares[k] must be the share
* of ids[k]. */
static void frost_enrollment_test_check_reconstruction(const uint32_t *ids, const unsigned char *const *shares, size_t n_ids, const secp256k1_pubkey *thresh_pk) {
secp256k1_scalar secret, share, lambda;
secp256k1_ge pk, expected;
secp256k1_gej pkj;
size_t i;
secp256k1_scalar_set_int(&secret, 0);
for (i = 0; i < n_ids; i++) {
CHECK(secp256k1_frost_derive_interpolating_value(&lambda, ids, n_ids, ids[i]) == 1);
CHECK(secp256k1_scalar_set_b32_seckey(&share, shares[i]) == 1);
secp256k1_scalar_mul(&share, &share, &lambda);
secp256k1_scalar_add(&secret, &secret, &share);
}
CHECK(!secp256k1_scalar_is_zero(&secret));
secp256k1_ecmult_gen_gej(&CTX->ecmult_gen_ctx, &pkj, &secret);
secp256k1_ge_set_gej(&pk, &pkj);
CHECK(secp256k1_pubkey_load(CTX, &expected, thresh_pk) == 1);
CHECK(secp256k1_ge_eq_var(&pk, &expected) == 1);
}
/* A 2-of-3 group grows to 2-of-4, and the new participant's share sits on the
* same polynomial as the old ones: every threshold-sized subset that contains
* it reconstructs the original threshold secret. */
static void run_frost_enrollment_smoke_test(void) {
frost_enrollment_test_run r;
const unsigned char *shares[2];
uint32_t ids[2];
size_t i;
frost_enrollment_test_full_run(&r, 3, 2, 2, 3);
/* The pair that ran the protocol, and every other pair including the new
* participant. */
for (i = 0; i < 3; i++) {
ids[0] = (uint32_t)i;
ids[1] = 3;
shares[0] = r.secshares[i];
shares[1] = r.new_secshare;
frost_enrollment_test_check_reconstruction(ids, shares, 2, &r.thresh_pk);
}
/* And the old group still reconstructs, unchanged. */
ids[0] = 0;
ids[1] = 1;
shares[0] = r.secshares[0];
shares[1] = r.secshares[1];
frost_enrollment_test_check_reconstruction(ids, shares, 2, &r.thresh_pk);
}
build: wire the frost_enrollment module into both build systems Second of six commits adding the frost_enrollment module. This one is scaffolding only: the five entry points are stubs that validate their pointer arguments, zero their outputs and return 0. What is being verified here is that the module configures, compiles, links, exports its symbols and registers its test module in both build systems -- so that the next commit changes nothing but arithmetic. Ordering is the one thing in this commit that can go silently wrong, and it goes wrong in opposite directions in the two build systems: - configure.ac executes its `if` blocks in file order, and enable_module_frost defaults to no (configure.ac:243). A block placed after the frost block at :601 that sets enable_module_frost=yes flips the variable too late: AM_CONDITIONAL goes true, so the header is installed and the Makefile fragment is pulled in, but -DENABLE_MODULE_FROST=1 is never appended, so src/secp256k1.c never includes frost's implementation and every secp256k1_frost_* symbol fails to link. The new block therefore goes ahead of both the frost block and prefractal's, which documents the same trap. - src/CMakeLists.txt processes dependents FIRST, so the same block goes above the FROST block there, beside prefractal's. Verified rather than assumed: configuring with ONLY --enable-module-frost-enrollment emits -DENABLE_MODULE_FROST=1 alongside -DENABLE_MODULE_FROST_ENROLLMENT=1, and the CMake summary prints "frost ON" for the same configuration -- the latter is what the PARENT_SCOPE lift buys, since the summary runs after add_subdirectory(src) and would otherwise report a module it is compiling in as OFF. The dependency guard is prefractal's implies-frost idiom, copied verbatim along with its reasoning. frost is default-OFF, so the `test x"$enable_module_frost" = x"no"` / `DEFINED X AND NOT X` guard every other module uses -- which reads as "the user disabled it explicitly" for a default-ON dependency -- is true by default here and cannot tell an explicit --disable-module-frost from the default once both are in the cache. Enabling frost-enrollment simply implies frost, with no error. The one frost-module change in the whole series is in this commit: src/modules/frost/session.h gains a declaration for secp256k1_frost_sort_ids, which is defined at session_impl.h:517 and declared nowhere. The params hash needs it to canonicalize identifier order. Prefractal reaches frost's statics through translation-unit ordering alone; rather than inherit reuse-by-link-order, this declares the function where keygen.h:48 already declares derive_pubshare_at, so the reuse goes through an interface. No behavior change: it is a declaration for an existing static definition in the same TU. CI wiring is two files, and skipping either half fails quietly: - ci/ci.sh gets FROST_ENROLLMENT in the reproduction header's variable list and --enable-module-frost-enrollment="$FROST_ENROLLMENT" after the prefractal line. - .github/workflows/ci.yml gets FROST_ENROLLMENT at every PREFRACTAL site: the global default, 11 inline matrix entries and 10 job-level env blocks. Without the default, ci.sh runs under set -eux with an empty $FROST_ENROLLMENT, passes --enable-module-frost-enrollment="", `test x"" = x"yes"` is false, and the module is off in all of CI while ci.sh visibly has the plumbing. Verified programmatically over the parsed workflow: across the 106 effective job contexts, PREFRACTAL and FROST_ENROLLMENT now agree in every single one (45 set to yes, no mismatches), no context sets FROST_ENROLLMENT without FROST or without EXPERIMENTAL, and no context leaves it undefined. ci.sh passes sh -n. The stub test is not a placeholder that has to be deleted later: every entry point must reject an empty helper set and leave its output zeroed, which is true of the stubs and stays true of the finished implementation, so it doubles as the check that all five symbols are reachable from the test binary. Verification. Autotools: ./autogen.sh, then a frost-enrollment-only configure and a full configure with frost, chilldkg, iceberg, prefractal and frost-enrollment all on -- both build with zero warnings under the project's -Werror-grade flag set, ./tests and ./exhaustive_tests exit 0, and `./tests -l` lists the frost_enrollment module. CMake: configure with -DSECP256K1_EXPERIMENTAL=ON -DSECP256K1_ENABLE_MODULE_FROST_ENROLLMENT=ON builds clean and ctest passes 391 tests. nm shows the five new symbols exported from libsecp256k1.so; tools/symbol-check.py could not be run here because python3-lief is not installed in this environment, but all five carry the required secp256k1_ prefix. make dist succeeds and the tarball carries src/modules/frost_enrollment/frost_enrollment.md alongside the other module documents. One unrelated observation from this build: a stale src/ctime_tests-ctime_tests.o left over from an earlier configure with a different module set will fail to link, because automake does not track CPPFLAGS changes across reconfigures. make clean between configurations with different module sets, not a fault in this change. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-09-04 03:53:03 +02:00
/* Every entry point must reject an empty helper set and leave its output
frost_enrollment: implement the three rounds Third of six commits. Replaces the Phase 1 stubs with the real arithmetic, adds a smoke test that a 2-of-3 group really does grow into a working 2-of-4 one, and wires the entry points into ctime_tests. The Lagrange machinery is frost's, called in place. pubshare_derive is a skin over secp256k1_frost_derive_pubshare_at (src/modules/frost/keygen_impl.h:150) evaluated at identifier new_id, and the id canonicalization is secp256k1_frost_sort_ids, reached through the declaration the previous commit added. The one piece frost could not supply is the scalar Lagrange coefficient at an arbitrary point. frost's secp256k1_frost_derive_interpolating_value evaluates at x-coordinate 0, which is what reconstructing the group secret needs; enrollment needs the basis polynomial at the TARGET x-coordinate. secp256k1_frost_enrollment_lagrange_at is that, and it is deliberately the same product derive_pubshare_at applies to each pubshare, in the same identifier space -- so the scalar path and the point path agree by construction rather than by coincidence. Working in identifier space is what makes the id-to-x-coordinate +1 cancel: an x-coordinate difference x_j - x_i is the identifier difference id_j - id_i. Round 1.1 computes v = lambda * secshare and splits it. Every share but the one kept locally is masking randomness derived as Scalar.from_bytes_wrapping( TH("FROST enrollment/share_split", rand32 || params_hash32 || ser32(my_id) || ser32(recipient_id))) with rand32 = TH(same tag, session_secrand32) XOR secshare32; the kept share absorbs the remainder so the set sums to v. Three details: - The reduction wraps rather than rejects, chilldkg's from_bytes_wrapping (src/modules/chilldkg/util_impl.h:394). A 256-bit hash mod the group order is about 2^-128 from uniform; rejection sampling would buy that back in exchange for a variable-time loop. - Masking with the secret share is the secp256k1_frost_nonce_gen pattern (session_impl.h:340), so a broken RNG alone does not reveal the split. - The derivation is indexed by the recipient's IDENTIFIER, not by its position in the caller's ids array. The plan called for a counter; identifiers are unique, so they are one, and using them makes the split independent of the order a caller lists the helper set in. What the binding buys is DOMAIN SEPARATION only: params_hash32 carries the group key and the whole parameter tuple, so two runs sharing a seed but differing in either cannot produce the same deltas. It cannot detect a disagreement between helpers, because nothing cross-checks per-helper private randomness. That is the params hash's job. session_secrand32 is wiped whether the call succeeds or fails, so a caller cannot retry a failed run on the same randomness. Round 1.2 recomputes its own params hash from the group key and the tuple, compares every received hash against it, then sums. The slot at the caller's own position in received_params_hashes32 is skipped, while the same position in all_shares32 is read -- the asymmetry the header documents, and the thing that makes this a recomputation rather than a string comparison. The mode and bounds are re-validated here rather than trusted from the round 1.1 call site, since the full tuple is present. An out-of-range share is reported through mismatch_id the way secp256k1_frost_partial_sig_agg reports an unparseable partial signature. Round 2 compares the params hash against its own recomputation over the authenticated group key, sums, rejects a zero share, and checks secshare*G against the expected public share. Three deviations from the plan, all to match what the tree already does: - Value ranges return 0; only pointers get ARG_CHECK. The plan called for an ARG_CHECK on the n_ids bound, but the frost module's split is the one used here (secp256k1_frost_trusted_dealer_keygen, keygen_impl.h:227), and the header already documents these as return-0 conditions. The bound is still enforced in production builds -- params_are_valid requires 2 <= threshold <= n_ids <= n_participants <= 128 -- so it does not ride on the VERIFY_CHECK inside secp256k1_frost_sort_ids, which is what the plan was guarding against. - The public-share check declassifies the derived point and compares with secp256k1_ge_eq_var, rather than comparing 33 serialized bytes in constant time. There is no constant-time memcmp in this tree, and secshare*G is a public key: secp256k1_frost_sign declassifies exactly this quantity before exactly this comparison (src/modules/frost/session_impl.h:770, :789). Inventing a primitive to avoid following that precedent would be the worse trade. - params_hash's public entry point delegates to the same internal routine every gate uses, so the encoding has exactly one implementation to keep in step with the vectors. One real bug found by the tooling rather than by reading. Accumulators were initialized with secp256k1_scalar_clear, and secp256k1_memclear_explicit marks its target UNDEFINED in VERIFY builds (src/util.h:295) precisely so that reading cleared memory is caught. It was: valgrind reported 143752 errors in share_agg's summation loop. Accumulators now start at secp256k1_scalar_set_int(x, 0); scalar_clear is used only where it means "done with this secret". Worth stating plainly because the failure mode is invisible in a production build, where memclear_explicit only zeroes. ctime_tests gains a 2-of-3-enrolls-a-fourth block covering all three rounds, following prefractal's b66c757b. The threshold key, the secret shares, the session randomness and every delta and sigma on the wire are marked secret; the identifiers, public shares, group key, parameters hashes and derived public share are not. Under valgrind: 0 errors from 0 contexts, so no branch or memory access in the new code depends on secret data. Verification: ./tests, ./noverify_tests and ./exhaustive_tests exit 0; the frost_enrollment module runs clean under valgrind (0 errors); a separate CPPFLAGS='-DVERIFY' build compiles without warnings and passes; the module builds warning-free alongside frost, chilldkg, iceberg and prefractal. The smoke test is the substantive check: after a 2-of-3 group enrolls participant 3, every pair {i, 3} for i in 0..2 reconstructs the original threshold secret and matches the threshold public key, and the untouched pair {0, 1} still does too. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-09-04 04:06:59 +02:00
* zeroed. This also checks that all five symbols are reachable from the test
* binary. */
build: wire the frost_enrollment module into both build systems Second of six commits adding the frost_enrollment module. This one is scaffolding only: the five entry points are stubs that validate their pointer arguments, zero their outputs and return 0. What is being verified here is that the module configures, compiles, links, exports its symbols and registers its test module in both build systems -- so that the next commit changes nothing but arithmetic. Ordering is the one thing in this commit that can go silently wrong, and it goes wrong in opposite directions in the two build systems: - configure.ac executes its `if` blocks in file order, and enable_module_frost defaults to no (configure.ac:243). A block placed after the frost block at :601 that sets enable_module_frost=yes flips the variable too late: AM_CONDITIONAL goes true, so the header is installed and the Makefile fragment is pulled in, but -DENABLE_MODULE_FROST=1 is never appended, so src/secp256k1.c never includes frost's implementation and every secp256k1_frost_* symbol fails to link. The new block therefore goes ahead of both the frost block and prefractal's, which documents the same trap. - src/CMakeLists.txt processes dependents FIRST, so the same block goes above the FROST block there, beside prefractal's. Verified rather than assumed: configuring with ONLY --enable-module-frost-enrollment emits -DENABLE_MODULE_FROST=1 alongside -DENABLE_MODULE_FROST_ENROLLMENT=1, and the CMake summary prints "frost ON" for the same configuration -- the latter is what the PARENT_SCOPE lift buys, since the summary runs after add_subdirectory(src) and would otherwise report a module it is compiling in as OFF. The dependency guard is prefractal's implies-frost idiom, copied verbatim along with its reasoning. frost is default-OFF, so the `test x"$enable_module_frost" = x"no"` / `DEFINED X AND NOT X` guard every other module uses -- which reads as "the user disabled it explicitly" for a default-ON dependency -- is true by default here and cannot tell an explicit --disable-module-frost from the default once both are in the cache. Enabling frost-enrollment simply implies frost, with no error. The one frost-module change in the whole series is in this commit: src/modules/frost/session.h gains a declaration for secp256k1_frost_sort_ids, which is defined at session_impl.h:517 and declared nowhere. The params hash needs it to canonicalize identifier order. Prefractal reaches frost's statics through translation-unit ordering alone; rather than inherit reuse-by-link-order, this declares the function where keygen.h:48 already declares derive_pubshare_at, so the reuse goes through an interface. No behavior change: it is a declaration for an existing static definition in the same TU. CI wiring is two files, and skipping either half fails quietly: - ci/ci.sh gets FROST_ENROLLMENT in the reproduction header's variable list and --enable-module-frost-enrollment="$FROST_ENROLLMENT" after the prefractal line. - .github/workflows/ci.yml gets FROST_ENROLLMENT at every PREFRACTAL site: the global default, 11 inline matrix entries and 10 job-level env blocks. Without the default, ci.sh runs under set -eux with an empty $FROST_ENROLLMENT, passes --enable-module-frost-enrollment="", `test x"" = x"yes"` is false, and the module is off in all of CI while ci.sh visibly has the plumbing. Verified programmatically over the parsed workflow: across the 106 effective job contexts, PREFRACTAL and FROST_ENROLLMENT now agree in every single one (45 set to yes, no mismatches), no context sets FROST_ENROLLMENT without FROST or without EXPERIMENTAL, and no context leaves it undefined. ci.sh passes sh -n. The stub test is not a placeholder that has to be deleted later: every entry point must reject an empty helper set and leave its output zeroed, which is true of the stubs and stays true of the finished implementation, so it doubles as the check that all five symbols are reachable from the test binary. Verification. Autotools: ./autogen.sh, then a frost-enrollment-only configure and a full configure with frost, chilldkg, iceberg, prefractal and frost-enrollment all on -- both build with zero warnings under the project's -Werror-grade flag set, ./tests and ./exhaustive_tests exit 0, and `./tests -l` lists the frost_enrollment module. CMake: configure with -DSECP256K1_EXPERIMENTAL=ON -DSECP256K1_ENABLE_MODULE_FROST_ENROLLMENT=ON builds clean and ctest passes 391 tests. nm shows the five new symbols exported from libsecp256k1.so; tools/symbol-check.py could not be run here because python3-lief is not installed in this environment, but all five carry the required secp256k1_ prefix. make dist succeeds and the tarball carries src/modules/frost_enrollment/frost_enrollment.md alongside the other module documents. One unrelated observation from this build: a stale src/ctime_tests-ctime_tests.o left over from an earlier configure with a different module set will fail to link, because automake does not track CPPFLAGS changes across reconfigures. make clean between configurations with different module sets, not a fault in this change. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-09-04 03:53:03 +02:00
static void run_frost_enrollment_rejects_empty_set_test(void) {
secp256k1_pubkey pk;
secp256k1_pubkey pubshare;
unsigned char buf32[32];
unsigned char secrand32[32];
unsigned char hash32[32];
uint32_t ids[1] = { 0 };
memset(&pk, 0, sizeof(pk));
memset(&pubshare, 0xff, sizeof(pubshare));
memset(secrand32, 0x11, sizeof(secrand32));
memset(buf32, 0xff, sizeof(buf32));
CHECK(secp256k1_frost_enrollment_params_hash(CTX, buf32, &pk, ids, 0, 0, 1, 2) == 0);
CHECK(secp256k1_is_zero_array(buf32, sizeof(buf32)));
memset(buf32, 0xff, sizeof(buf32));
memset(hash32, 0xff, sizeof(hash32));
CHECK(secp256k1_frost_enrollment_shares_gen(CTX, buf32, hash32, secrand32, buf32, &pk, ids, 0, 0, 1, 1, 2) == 0);
CHECK(secp256k1_is_zero_array(hash32, sizeof(hash32)));
memset(buf32, 0xff, sizeof(buf32));
CHECK(secp256k1_frost_enrollment_share_agg(CTX, buf32, NULL, buf32, hash32, &pk, ids, 0, 0, 1, 1, 2) == 0);
CHECK(secp256k1_is_zero_array(buf32, sizeof(buf32)));
CHECK(secp256k1_frost_enrollment_pubshare_derive(CTX, &pubshare, &pk, ids, 0, 0, 1, 2) == 0);
CHECK(secp256k1_is_zero_array((unsigned char *)&pubshare, sizeof(pubshare)));
memset(buf32, 0xff, sizeof(buf32));
CHECK(secp256k1_frost_enrollment_secshare_gen(CTX, buf32, buf32, &pk, ids, 0, 0, 1, 2, NULL, NULL) == 0);
CHECK(secp256k1_is_zero_array(buf32, sizeof(buf32)));
}
static const struct tf_test_entry tests_frost_enrollment[] = {
frost_enrollment: implement the three rounds Third of six commits. Replaces the Phase 1 stubs with the real arithmetic, adds a smoke test that a 2-of-3 group really does grow into a working 2-of-4 one, and wires the entry points into ctime_tests. The Lagrange machinery is frost's, called in place. pubshare_derive is a skin over secp256k1_frost_derive_pubshare_at (src/modules/frost/keygen_impl.h:150) evaluated at identifier new_id, and the id canonicalization is secp256k1_frost_sort_ids, reached through the declaration the previous commit added. The one piece frost could not supply is the scalar Lagrange coefficient at an arbitrary point. frost's secp256k1_frost_derive_interpolating_value evaluates at x-coordinate 0, which is what reconstructing the group secret needs; enrollment needs the basis polynomial at the TARGET x-coordinate. secp256k1_frost_enrollment_lagrange_at is that, and it is deliberately the same product derive_pubshare_at applies to each pubshare, in the same identifier space -- so the scalar path and the point path agree by construction rather than by coincidence. Working in identifier space is what makes the id-to-x-coordinate +1 cancel: an x-coordinate difference x_j - x_i is the identifier difference id_j - id_i. Round 1.1 computes v = lambda * secshare and splits it. Every share but the one kept locally is masking randomness derived as Scalar.from_bytes_wrapping( TH("FROST enrollment/share_split", rand32 || params_hash32 || ser32(my_id) || ser32(recipient_id))) with rand32 = TH(same tag, session_secrand32) XOR secshare32; the kept share absorbs the remainder so the set sums to v. Three details: - The reduction wraps rather than rejects, chilldkg's from_bytes_wrapping (src/modules/chilldkg/util_impl.h:394). A 256-bit hash mod the group order is about 2^-128 from uniform; rejection sampling would buy that back in exchange for a variable-time loop. - Masking with the secret share is the secp256k1_frost_nonce_gen pattern (session_impl.h:340), so a broken RNG alone does not reveal the split. - The derivation is indexed by the recipient's IDENTIFIER, not by its position in the caller's ids array. The plan called for a counter; identifiers are unique, so they are one, and using them makes the split independent of the order a caller lists the helper set in. What the binding buys is DOMAIN SEPARATION only: params_hash32 carries the group key and the whole parameter tuple, so two runs sharing a seed but differing in either cannot produce the same deltas. It cannot detect a disagreement between helpers, because nothing cross-checks per-helper private randomness. That is the params hash's job. session_secrand32 is wiped whether the call succeeds or fails, so a caller cannot retry a failed run on the same randomness. Round 1.2 recomputes its own params hash from the group key and the tuple, compares every received hash against it, then sums. The slot at the caller's own position in received_params_hashes32 is skipped, while the same position in all_shares32 is read -- the asymmetry the header documents, and the thing that makes this a recomputation rather than a string comparison. The mode and bounds are re-validated here rather than trusted from the round 1.1 call site, since the full tuple is present. An out-of-range share is reported through mismatch_id the way secp256k1_frost_partial_sig_agg reports an unparseable partial signature. Round 2 compares the params hash against its own recomputation over the authenticated group key, sums, rejects a zero share, and checks secshare*G against the expected public share. Three deviations from the plan, all to match what the tree already does: - Value ranges return 0; only pointers get ARG_CHECK. The plan called for an ARG_CHECK on the n_ids bound, but the frost module's split is the one used here (secp256k1_frost_trusted_dealer_keygen, keygen_impl.h:227), and the header already documents these as return-0 conditions. The bound is still enforced in production builds -- params_are_valid requires 2 <= threshold <= n_ids <= n_participants <= 128 -- so it does not ride on the VERIFY_CHECK inside secp256k1_frost_sort_ids, which is what the plan was guarding against. - The public-share check declassifies the derived point and compares with secp256k1_ge_eq_var, rather than comparing 33 serialized bytes in constant time. There is no constant-time memcmp in this tree, and secshare*G is a public key: secp256k1_frost_sign declassifies exactly this quantity before exactly this comparison (src/modules/frost/session_impl.h:770, :789). Inventing a primitive to avoid following that precedent would be the worse trade. - params_hash's public entry point delegates to the same internal routine every gate uses, so the encoding has exactly one implementation to keep in step with the vectors. One real bug found by the tooling rather than by reading. Accumulators were initialized with secp256k1_scalar_clear, and secp256k1_memclear_explicit marks its target UNDEFINED in VERIFY builds (src/util.h:295) precisely so that reading cleared memory is caught. It was: valgrind reported 143752 errors in share_agg's summation loop. Accumulators now start at secp256k1_scalar_set_int(x, 0); scalar_clear is used only where it means "done with this secret". Worth stating plainly because the failure mode is invisible in a production build, where memclear_explicit only zeroes. ctime_tests gains a 2-of-3-enrolls-a-fourth block covering all three rounds, following prefractal's b66c757b. The threshold key, the secret shares, the session randomness and every delta and sigma on the wire are marked secret; the identifiers, public shares, group key, parameters hashes and derived public share are not. Under valgrind: 0 errors from 0 contexts, so no branch or memory access in the new code depends on secret data. Verification: ./tests, ./noverify_tests and ./exhaustive_tests exit 0; the frost_enrollment module runs clean under valgrind (0 errors); a separate CPPFLAGS='-DVERIFY' build compiles without warnings and passes; the module builds warning-free alongside frost, chilldkg, iceberg and prefractal. The smoke test is the substantive check: after a 2-of-3 group enrolls participant 3, every pair {i, 3} for i in 0..2 reconstructs the original threshold secret and matches the threshold public key, and the untouched pair {0, 1} still does too. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-09-04 04:06:59 +02:00
CASE1(run_frost_enrollment_smoke_test),
build: wire the frost_enrollment module into both build systems Second of six commits adding the frost_enrollment module. This one is scaffolding only: the five entry points are stubs that validate their pointer arguments, zero their outputs and return 0. What is being verified here is that the module configures, compiles, links, exports its symbols and registers its test module in both build systems -- so that the next commit changes nothing but arithmetic. Ordering is the one thing in this commit that can go silently wrong, and it goes wrong in opposite directions in the two build systems: - configure.ac executes its `if` blocks in file order, and enable_module_frost defaults to no (configure.ac:243). A block placed after the frost block at :601 that sets enable_module_frost=yes flips the variable too late: AM_CONDITIONAL goes true, so the header is installed and the Makefile fragment is pulled in, but -DENABLE_MODULE_FROST=1 is never appended, so src/secp256k1.c never includes frost's implementation and every secp256k1_frost_* symbol fails to link. The new block therefore goes ahead of both the frost block and prefractal's, which documents the same trap. - src/CMakeLists.txt processes dependents FIRST, so the same block goes above the FROST block there, beside prefractal's. Verified rather than assumed: configuring with ONLY --enable-module-frost-enrollment emits -DENABLE_MODULE_FROST=1 alongside -DENABLE_MODULE_FROST_ENROLLMENT=1, and the CMake summary prints "frost ON" for the same configuration -- the latter is what the PARENT_SCOPE lift buys, since the summary runs after add_subdirectory(src) and would otherwise report a module it is compiling in as OFF. The dependency guard is prefractal's implies-frost idiom, copied verbatim along with its reasoning. frost is default-OFF, so the `test x"$enable_module_frost" = x"no"` / `DEFINED X AND NOT X` guard every other module uses -- which reads as "the user disabled it explicitly" for a default-ON dependency -- is true by default here and cannot tell an explicit --disable-module-frost from the default once both are in the cache. Enabling frost-enrollment simply implies frost, with no error. The one frost-module change in the whole series is in this commit: src/modules/frost/session.h gains a declaration for secp256k1_frost_sort_ids, which is defined at session_impl.h:517 and declared nowhere. The params hash needs it to canonicalize identifier order. Prefractal reaches frost's statics through translation-unit ordering alone; rather than inherit reuse-by-link-order, this declares the function where keygen.h:48 already declares derive_pubshare_at, so the reuse goes through an interface. No behavior change: it is a declaration for an existing static definition in the same TU. CI wiring is two files, and skipping either half fails quietly: - ci/ci.sh gets FROST_ENROLLMENT in the reproduction header's variable list and --enable-module-frost-enrollment="$FROST_ENROLLMENT" after the prefractal line. - .github/workflows/ci.yml gets FROST_ENROLLMENT at every PREFRACTAL site: the global default, 11 inline matrix entries and 10 job-level env blocks. Without the default, ci.sh runs under set -eux with an empty $FROST_ENROLLMENT, passes --enable-module-frost-enrollment="", `test x"" = x"yes"` is false, and the module is off in all of CI while ci.sh visibly has the plumbing. Verified programmatically over the parsed workflow: across the 106 effective job contexts, PREFRACTAL and FROST_ENROLLMENT now agree in every single one (45 set to yes, no mismatches), no context sets FROST_ENROLLMENT without FROST or without EXPERIMENTAL, and no context leaves it undefined. ci.sh passes sh -n. The stub test is not a placeholder that has to be deleted later: every entry point must reject an empty helper set and leave its output zeroed, which is true of the stubs and stays true of the finished implementation, so it doubles as the check that all five symbols are reachable from the test binary. Verification. Autotools: ./autogen.sh, then a frost-enrollment-only configure and a full configure with frost, chilldkg, iceberg, prefractal and frost-enrollment all on -- both build with zero warnings under the project's -Werror-grade flag set, ./tests and ./exhaustive_tests exit 0, and `./tests -l` lists the frost_enrollment module. CMake: configure with -DSECP256K1_EXPERIMENTAL=ON -DSECP256K1_ENABLE_MODULE_FROST_ENROLLMENT=ON builds clean and ctest passes 391 tests. nm shows the five new symbols exported from libsecp256k1.so; tools/symbol-check.py could not be run here because python3-lief is not installed in this environment, but all five carry the required secp256k1_ prefix. make dist succeeds and the tarball carries src/modules/frost_enrollment/frost_enrollment.md alongside the other module documents. One unrelated observation from this build: a stale src/ctime_tests-ctime_tests.o left over from an earlier configure with a different module set will fail to link, because automake does not track CPPFLAGS changes across reconfigures. make clean between configurations with different module sets, not a fault in this change. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-09-04 03:53:03 +02:00
CASE1(run_frost_enrollment_rejects_empty_set_test),
};
#endif /* SECP256K1_MODULE_FROST_ENROLLMENT_TESTS_IMPL_H */
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