Add the public participant-facing ChillDKG API to
include/secp256k1_chilldkg.h and the CertEq sub-protocol, completing
the participant side of the protocol (bip-frost-dkg v0.3.0-dev,
reference pinned at a91896883f85b159415ecf298d5e844879af112d).
New module files:
- certeq.h / certeq_impl.h: CertEq sub-protocol. Participants sign
pad33("BIP DKG/certeq message") || u32be(i) || eq_input with plain
BIP0340-tagged Schnorr signatures under their host key
(certeq_participant_step); verification is per-index against the
x-only hostpubkeys[i][1:33] exactly as the reference
(certeq_verify). The coordinator side reuses certeq_verify in
Phase 4.
Public API (all no-malloc, caller-allocated buffers, outputs zeroed on
failure, secret paths cleared):
- secp256k1_chilldkg_hostpubkey_gen: plain compressed host pubkey
generation; rejects zero / >= group order seckeys.
- secp256k1_chilldkg_params_hash: validates session params (participant
and threshold ranges, strictly compressed non-infinity pubkeys, no
duplicates) and computes TH("BIP DKG/params_hash", u32be(t) ||
hostpubkeys).
- Message-length helpers so callers can size buffers:
participant_msg1_len (33t+32n+97), coordinator_msg1_len
(162n+33(t-1)), participant_msg2_len (64), coordinator_msg2_len
(64n), recovery_data_len (4+33t+162n).
- secp256k1_chilldkg_participant_step1: full EncPedPop step1 with
seed=deckey=hostseckey; rejects zero randomness and hostseckeys not
matching the claimed hostpubkey (input errors, not protocol faults).
- secp256k1_chilldkg_participant_step2: parses and verifies cmsg1 via
the Phase 2 encpedpop/simplpedpop participant path, computes the
tweaked secshare/pubshares/threshold pubkey, appends enc_secshares
to eq_input (matching the reference for recovery consistency), and
emits the 64-byte CertEq signature.
- secp256k1_chilldkg_participant_finalize: re-verifies all n CertEq
signatures in the certificate, then outputs the 32-byte secshare,
33-byte threshold pubkey, n pubshares and the self-delimiting
recovery data (eq_input || cert).
Blame reporting without exceptions: public enum
secp256k1_chilldkg_fault (OK / FAULTY_COORDINATOR /
FAULTY_PARTICIPANT / FAULTY_PARTICIPANT_OR_COORDINATOR /
UNKNOWN_FAULTY_PARTICIPANT_OR_COORDINATOR / INVALID_INPUT) plus an out
fault_index, mapping the reference's exception taxonomy:
- hostseckey invalid/mismatch -> INVALID_INPUT (HostSeckeyError),
- cmsg1 scalar overflow/parse -> FAULTY_COORDINATOR (MsgParseError),
- pubnonce/commitment/PoP faults -> FAULTY_PARTICIPANT_OR_COORDINATOR(i),
- share-vs-pubshare mismatch -> UNKNOWN with fault_index = UINT32_MAX,
- certificate signature failure -> FAULTY_COORDINATOR (documented
deviation: fault_index carries the failing signature index as
diagnostic info; the reference discards it).
Enum-returning functions use a local CHILLDKG_ARG_CHECK that fires the
illegal-argument callback and returns INVALID_INPUT (ARG_CHECK would
return 0 = OK).
Opaque state objects with magic-validated save/load (frost idiom):
participant_state1 (4306 bytes, no secrets) and participant_state2
(21073 bytes, contains the secshare; documented keep-secret/no-copy).
Fixed-size at SECP256K1_CHILLDKG_MAX_PARTICIPANTS = 128.
Also fixes a noverify-build bug: state1_load ran point_load inside
VERIFY_CHECK, which compiles out in noverify builds and left the
commitment uninitialized; now called unconditionally.
tests_impl.h: participant_api_test with full-session reference vectors
(n=3, t=2; coordinator aggregation simulated through the internal
Phase 2 coordinator step and verified byte-identical to the
reference's coordinator_step1): msglen helpers, hostpubkey_gen and
params_hash vectors incl. duplicate/invalid/infinity rejection,
byte-exact pmsg1/cmsg1/CertEq sigs/secshare/thresh_pk/pubshares/
recovery, blame cases (tampered enc_secshare -> UNKNOWN, invalid
pubnonce -> FAULTY_PARTICIPANT_OR_COORDINATOR(1), overflowing
enc_secshare -> FAULTY_COORDINATOR, corrupted cert sig ->
FAULTY_COORDINATOR with fault_index and zeroed outputs), NULL-arg
misuse and bad-magic state rejection.
Verified: make check 3/3 (incl. noverify); CMake ctest 363/363;
make distdir includes all new files.
Add an empty, experimental `chilldkg` module as the foundation for a
ChillDKG implementation (distributed key generation for FROST) per the
bip-frost-dkg BIP draft (v0.3.0-dev):
https://github.com/BlockstreamResearch/bip-frost-dkg
The module lives in src/modules/chilldkg/ (separate from the frost
module, per the implementation plan in .idea/docs/
chilldkg-implementation-plan.md: FROST signing (BIP 445) and ChillDKG
are separate BIPs with separate reference repos, test vectors and
review cycles; the dependency between them is one-way bytes).
New files:
- include/secp256k1_chilldkg.h: public header skeleton with the same
"EXTREMELY DANGEROUS / work in progress" warning style as
secp256k1_frost.h, plus a note that the BIP is a draft and tagged
hashes/wire formats may change. No API yet (Phase 3+).
- src/modules/chilldkg/main_impl.h: implementation skeleton including
the public header.
- src/modules/chilldkg/tests_impl.h: trivial scaffolding unit test
(chilldkg_scaffolding_test) registered via the tests_chilldkg[]
CASE1 array used by this repo's unit-test framework.
- src/modules/chilldkg/Makefile.am.include: autotools file list,
mirroring the frost module's.
- src/modules/chilldkg/chilldkg.md: module doc stub (purpose, draft
status, dependency on the schnorrsig and ecdh modules).
Build wiring (mirrors the frost module exactly):
- configure.ac: --enable-module-chilldkg (default no, experimental
gate), dependency errors when schnorrsig or ecdh are explicitly
disabled, AM_CONDITIONAL(ENABLE_MODULE_CHILLDKG), summary line.
- Makefile.am: include src/modules/chilldkg/Makefile.am.include under
ENABLE_MODULE_CHILLDKG.
- src/secp256k1.c: guarded include of modules/chilldkg/main_impl.h
after the frost module.
- src/tests.c: guarded include of tests_impl.h and
MAKE_TEST_MODULE(chilldkg) registration.
- CMakeLists.txt: SECP256K1_ENABLE_MODULE_CHILLDKG option (OFF) +
summary line.
- src/CMakeLists.txt: dependency checks on
SECP256K1_ENABLE_MODULE_SCHNORRSIG and SECP256K1_ENABLE_MODULE_ECDH,
ENABLE_MODULE_CHILLDKG=1 compile definition, public header export.
Verified:
- ./autogen.sh && ./configure --enable-experimental
--enable-module-chilldkg --enable-module-schnorrsig
--enable-module-ecdh && make check: PASS 3/3 (tests, noverify_tests,
exhaustive_tests).
- configure fails with a clear error when schnorrsig or ecdh are
disabled, or when experimental is not enabled.
- CMake build with SECP256K1_ENABLE_MODULE_CHILLDKG=ON: ctest 345/345
passed; dependency errors fire correctly when schnorrsig/ecdh OFF.
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Four small divergences from the reference implementation and its API
contract, none of which changes any signature: the differential harness
(240 signing + 120 deterministic-signing cases against the Python
reference) produces byte-identical output before and after.
Length prefixes that do not fit
-------------------------------
secp256k1_frost_sha256_write_prefixed asserted, via VERIFY_CHECK, that
the length fits into its prefix. VERIFY_CHECK compiles away in release
builds, so a length that does not fit was silently truncated modulo
2^(8*prefix_size) instead of being rejected, yielding a nonce that does
not follow the spec. The reference raises OverflowError instead.
Only the 4-byte extra_in prefix of nonce_hash is affected, and only where
size_t is wider than 32 bits, so this needs an extra_in of 4 GiB to
trigger. It is nevertheless a silent deviation, so write_prefixed now
returns 0 without writing anything, and the failure is propagated:
secp256k1_frost_nonce_function and secp256k1_frost_det_nonce_function
return 0, and secp256k1_frost_nonce_gen returns 0 after wiping
session_secrand32 and the nonces. Checking the shifted-out bits (which
the loop already computes) rather than comparing extra_in_len against a
32-bit bound avoids a comparison that is always true on 32-bit platforms.
The bound is now documented on the extra_in_len parameter.
Identifiers equal to UINT32_MAX
-------------------------------
BIP 445 derive_interpolating_value accepts every identifier in
0 <= id < 2^32, but secp256k1_frost_ids_are_valid rejected UINT32_MAX
because the mapping to the polynomial x-coordinate, id + 1, overflows in
uint32_t arithmetic. The +1 is now added in scalar arithmetic, where it
cannot overflow, and the identifier restriction is gone. The denominator
never needed the +1 at all, since
x_j - x_i = (id_j + 1) - (my_id + 1) = id_j - my_id
so it is computed directly from the identifiers.
This was unreachable through the public API -- validate_session_params
already bounds identifiers by n_participants, which is at most
SECP256K1_FROST_MAX_PARTICIPANTS = 128 -- but it made an internal helper
diverge from the algorithm it implements. frost_large_id_test covers it
by reconstructing the constant term of a random degree-2 polynomial from
shares held by identifiers 0, UINT32_MAX - 1 and UINT32_MAX.
Zero-length messages
--------------------
secp256k1_frost_session_init and secp256k1_frost_deterministic_sign
required a non-NULL msg, so an empty message -- which the reference
represents as the byte string b"" -- could only be passed as a pointer
that is never dereferenced. Both now accept NULL when msglen is 0,
matching secp256k1_schnorrsig_sign_custom and the msg parameter of
secp256k1_frost_nonce_gen. secp256k1_sha256_write guards both of its
memcpy calls on a non-zero length, so it is never reached with a NULL
pointer.
NonceGen keeps its distinction between a NULL msg and a zero-length msg:
there the BIP really does distinguish msg = None (hashed as the single
byte 0x00) from msg = b"" (hashed as 0x01 followed by an eight-byte zero
length), and the API expresses that as NULL versus non-NULL.
frost_empty_msg_test runs a signing round over a zero-length message
passed both ways and checks that the two session objects are identical.
The two API tests that relied on a NULL msg always being rejected now
pass an explicit non-zero msglen; previously they passed a random msglen
that could be 0.
Header documentation
--------------------
The parameter tables of eleven doc comments had names that did not line
up with their block's continuation column. All parameter tables are now
aligned consistently, with wrapped text two columns past the colon.
Verification
------------
- gcc and clang, -std=c89 -pedantic-errors -Werror, with and without
-DVERIFY: clean
- tests (multiple seeds), noverify_tests and frost_example: pass
- ctime_tests under MemorySanitizer: exits 0 with halt_on_error=1
- vectors.h still reproduces exactly from the spec's JSON vectors
- 240 signing + 120 deterministic-signing differential cases against
the BIP 445 Python reference: byte-identical to the previous commit
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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This introduces `secp256k1_context_set_sha256_compression()`,
which allows users to provide their own SHA256 block-compression
function at runtime.
This is useful in setups where the fastest implementation can only
be determined dynamically based on the available CPU features, and
rebuilding the library is not possible.
The callback is installed on the `secp256k1_context` and is then used
by all operations that compute SHA256 hashes. As part of the setup,
the library performs sanity checks to ensure that the supplied
function is equivalent to the default transform.
Passing NULL to the callback setter restores the built-in
implementation.
dc0bda5731 bench: Port bitcoin-core/secp256k1#1796 to zkp-specific code (mllwchrry)
fe48cc9fa5 generator: Port bitcoin-core/secp256k1#1764 to zkp-specific code (mllwchrry)
d111d31293 generator: Port bitcoin-core/secp256k1#1779 to zkp-specific code (mllwchrry)
d8e87e45f3 unit_test: bump MAX_ARGS from 150 to 200 (mllwchrry)
2542b43451 modules: Port bitcoin-core/secp256k1#1774 to zkp-specific code (mllwchrry)
ae7eb729c0 release cleanup: bump version after 0.7.1 (Jonas Nick)
20a209f11c release: prepare for 0.7.1 (Jonas Nick)
c4b6a81a60 changelog: update in preparation for the v0.7.1 release (Jonas Nick)
c09215f7af bench: fail early if user inputs invalid value for SECP256K1_BENCH_ITERS (kevkevinpal)
29ac4d8491 sage: verify Eisenstein integer connection for GLV constants (Justsomebuddy)
bd5ced1fe1 doc/bench: added help text for SECP256K1_BENCH_ITERS env var for bench_ecmult (kevkevinpal)
2f73e5281d group: Avoid using infinity field directly in other modules (Tim Ruffing)
0406cfc4d1 doc: include arg -DUSE_EXTERNAL_DEFAULT_CALLBACKS=1 for cmake (kevkevinpal)
ae00c552df Add VERIFY_CHECKs that flags are 0 or 1 (John Moffett)
3b5b03f301 doc/bench: Added cmake build options to bench error messages (kevkevinpal)
d822b29021 test: split monolithic ellswift test into independent cases (furszy)
3daab83a60 refactor: remove ret from secp256k1_ec_pubkey_serialize (kevkevinpal)
8bcda186d2 test: Add non-NULL checks for "pointer of array" API functions (Sebastian Falbesoner)
5a08c1bcdc Add ARG_CHECKs to ensure "array of pointers" elements are non-NULL (Sebastian Falbesoner)
f5e815f430 remove secp256k1_eckey_pubkey_serialize function (Sebastian Falbesoner)
0d3659c547 use new `_eckey_pubkey_serialize{33,65}` functions in modules (ellswift,musig) (Sebastian Falbesoner)
adb76f82ea use new `_eckey_pubkey_serialize{33,65}` functions in public API (Sebastian Falbesoner)
fc7458ca3e introduce `secp256k1_eckey_pubkey_serialize{33,65}` functions (Sebastian Falbesoner)
26166c4f5f ecmult_multi: reduce strauss memory usage by 30% (Jonas Nick)
f252da7e6e ci: Use Python virtual environment in "x86_64-macos-native" job (Hennadii Stepanov)
153eea20c2 bench: Use `ALIGNMENT` macro instead of hardcoded value (Hennadii Stepanov)
Pull request description:
Merge bitcoin-core/secp256k1#1763: bench: Use `ALIGNMENT` macro instead of hardcoded value
Merge bitcoin-core/secp256k1#1771: ci: Use Python virtual environment in "x86_64-macos-native" job
Merge bitcoin-core/secp256k1#1761: ecmult_multi: reduce strauss memory usage by 30%
Merge bitcoin-core/secp256k1#1774: refactor: split up internal pubkey serialization function into compressed/uncompressed variants
Merge bitcoin-core/secp256k1#1779: Add ARG_CHECKs to ensure "array of pointers" elements are non-NULL
Merge bitcoin-core/secp256k1#1784: refactor: remove ret from secp256k1_ec_pubkey_serialize
Merge bitcoin-core/secp256k1#1788: test: split monolithic ellswift test into independent cases
Merge bitcoin-core/secp256k1#1778: doc/bench: Added cmake build options to bench error messages
Merge bitcoin-core/secp256k1#1783: Add VERIFY_CHECKs and documentation that flags must be 0 or 1
Merge bitcoin-core/secp256k1#1790: doc: include arg -DSECP256K1_USE_EXTERNAL_DEFAULT_CALLBACKS=ON for cmake
Merge bitcoin-core/secp256k1#1764: group: Avoid using infinity field directly in other modules
Merge bitcoin-core/secp256k1#1793: doc/bench: added help text for SECP256K1_BENCH_ITERS env var for bench_ecmult
Merge bitcoin-core/secp256k1#1800: sage: verify Eisenstein integer connection for GLV constants
Merge bitcoin-core/secp256k1#1796: bench: fail early if user inputs invalid value for SECP256K1_BENCH_ITERS
Merge bitcoin-core/secp256k1#1808: Prepare for 0.7.1
Merge bitcoin-core/secp256k1#1809: release cleanup: bump version after 0.7.1
This PR can be recreated with `./contrib/sync-upstream.sh -b master range c7a52400`.
Tips:
* Use `git show --remerge-diff <pr-branch>` to show the conflict resolution in the merge commit.
* Use `git read-tree --reset -u <pr-branch>` to replay these resolutions during the conflict resolution stage when recreating the PR branch locally.
Be aware that this may discard your index as well as the uncommitted changes and untracked files in your worktree.
ACKs for top commit:
real-or-random:
ACK dc0bda5731
Tree-SHA512: a816729a8d3ce199154a1b670172f4639b03812071fd78db8e23dfad9a88a2fef882f30c9f34e1151ad79b85201fbb7eba890a572d68bb45ca8fb05496bc34e8
6f7c112cc8 include: add description of range proofs focusing on the differences between the implementation and the CA paper (Mykyta)
Pull request description:
Added the description of range proofs in Confidential Assets focusing on the differences between the description in the paper and the actual implementation.
ACKs for top commit:
real-or-random:
ACK 6f7c112cc8
Tree-SHA512: c8568883648d6d1f0cbbe9a9730b08512665a90106b974733eecfc3dc628361ff54785c67c355216157af5a63b7fefa52d49df400ccaeec9cbf14d40a600707f
4d90585fea docs: Improve API docs of _context_set_illegal_callback (Tim Ruffing)
895f53d1cf docs: Clarify that callback can be called more than once (Tim Ruffing)
Pull request description:
The tests in #1698 reminded me that some functions, e.g., `secp256k1_ec_pubkey_cmp`, may call the illegal callback more than once (see https://github.com/bitcoin-core/secp256k1/pull/1390#discussion_r1279194655 for more context). This PR clarifies the API docs to state explicitly that this is possible.
This is the simplest solution. Any production code should crash anyway if it encounters a callback. And in debug code or in our test code, it doesn't really matter whether you see an error message once or twice.
The alternative is to provide a guarantee that the callback is called only once. But that would make our code more complex for no good reason.
The second commit fixes a few typos, wording, and consistency.
ACKs for top commit:
stratospher:
ACK 4d90585.
theStack:
re-ACK 4d90585fea
Tree-SHA512: 97c31d68851e845b21e9ec2530432603917c019580feba98b62014b538f61be94ba963bf619217720d8f7331ac830e97e62c76c02e7297d3cf73dd085e6f4ca2
This makes the usage of the atribute consistent. In the musig and ellswift
module, functions that return 1 always already don't have the WARN_UNUSED_RESULT
attribute. In secp256k1.h and the extrakeys module, this has only been the case
partially.
In all cases where this was removed, the function only returns 0 if the illegal
callback has been called.
These function aliases have been described as DEPRECATED in the public
API docs already many years ago (see #701, commit 41fc7856), and in
addition explicit deprecation warnings are shown by the compiler at
least since the first official release 0.2.0 (see PR #1089, commit
fc94a2da), so it should be fine to just remove them by now.
Co-authored-by: Tim Ruffing <crypto@timruffing.de>
447334cb06 include: Avoid visibility("default") on Windows (Tim Ruffing)
Pull request description:
Fixes#1421. See code comments for rationale.
Related meta-bug: #1181. This reminds me that we should move forward with #1359.
ACKs for top commit:
fanquake:
ACK 447334cb06
hebasto:
ACK 447334cb06, tested on Ubuntu 24.04 using the following commands:
theuni:
ACK 447334cb06
Tree-SHA512: aaa47d88fd1b1f85c3e879a2b288c0eb3beebad0cc89e85f05d0b631f83e58d5a324fb441911970865eaa292f6820d03a1b516d6e8de37a87510e2082acc6e28
168c92011f build: allow enabling the musig module in cmake (Jonas Nick)
f411841a46 Add module "musig" that implements MuSig2 multi-signatures (BIP 327) (Jonas Nick)
0be79660f3 util: add constant-time is_zero_array function (Jonas Nick)
c8fbdb1b97 group: add ge_to_bytes_ext and ge_from_bytes_ext (Jonas Nick)
85e224dd97 group: add ge_to_bytes and ge_from_bytes (Jonas Nick)
Pull request description:
EDIT: based on #1518. Closes#1452. Most of the code is a copy from [libsecp256k1-zkp](https://github.com/BlockstreamResearch/secp256k1-zkp). The API added in this PR is identical with the exception of two modifications:
1. I removed the unused `scratch_space` argument from `secp256k1_musig_pubkey_agg`. This argument was intended to allow using `ecmult_multi` algorithms for key aggregation in the future. But at this point it's unclear whether the `scratch_space` object will remain in its current form (see #1302).
2. Support for adaptor signatures was removed and therefore the `adaptor` argument of `musig_nonce_process` was also removed.
In contrast to the module in libsecp256k1-zkp, the module is non-experimental. I slightly cleaned up parts of the module, adjusted the code to the new definition of the VERIFY_CHECK macro and applied some simplifications that were possible because the module is now in the upstream repo (`ge_from_bytes`, `ge_to_bytes`). You can follow the changes I made to the libsecp256k1-zkp module at https://github.com/jonasnick/secp256k1-zkp/commits/musig2-upstream/.
ACKs for top commit:
sipa:
reACK 168c92011f
real-or-random:
reACK 168c92011f
theStack:
re-ACK 168c92011f
Tree-SHA512: e3a599a8d5a466107b9a86f76582b8fb9dc87ec95416c784c3ef39d1c64686e6c739806ed6ba62c91793eb7fa418a6270cf999027ee7bd3dd85c67bc2c74f677
