303a7caeae
Fourth of six commits. Twelve tests replacing the Phase 2 smoke test, plus
a vector generator and the frozen vectors it produces.
The regression vectors are the one part of this worth being precise
about, because they are easy to over-claim. FROST enrollment has no BIP
and no published vectors, and the reference proof of concept draws its
randomness from secrets.randbits, which is not seedable -- so there is
nothing to cross-validate against. tools/test_vectors_frost_enrollment_generate.py
therefore re-implements the math independently in stdlib-only Python,
including the group arithmetic written from the secp256k1 parameters
rather than borrowed, and freezes the output. What that buys: the two tag
strings, the params hash serialization, the share-splitting derivation
and the identifier conventions are now pinned, and changing any of them
is a loud vector-breaking change. What it does not buy is evidence of
protocol correctness. The generator header comment and the generated
file both say so, as does frost_enrollment.md.
The vectors passed on the first run against the C code, which is worth
recording: two independent implementations agree byte for byte on the
params hash, every delta, every sigma, the derived public share and the
final share, across four cases (2-of-3 minimal, 2-of-3 oversized at
u = 3 > t = 2, a 3-of-5 repair with a deliberately UNSORTED helper set,
and a 4-of-6 enrollment), covering both threshold-key Y parities.
The algebraic invariants are what actually carry correctness:
- Reconstruction (PoC test_generate_frost_share): after a 2-of-3 group
enrolls id 3, every pair {i, 3} reconstructs the original threshold
secret, and so does the untouched pair {0, 1}.
- Signing (PoC test_sign): a real BIP340 signature from {2, 3} verifying
against the unchanged threshold public key, with every partial
signature individually verified, plus the n -> n+1 bookkeeping --
secp256k1_frost_threshold_info_validate must accept the public share
table extended with pubshare_derive's output at n+1.
- Repair: byte-for-byte equality with the lost share, and the repaired
participant keeps its old public share.
- Oversized helper set: u = 3 and u = 2 over the same key material
produce the same share and the same derived public share.
- Randomized: COUNT iterations over 2 <= t <= u <= n <= 7, half
enrollment and half repair, with EVERY HELPER GIVEN THE IDENTIFIER SET
IN ITS OWN SHUFFLED ORDER. The params hash must come out identical
while the delta buffers stay aligned per helper -- which is the whole
point of canonicalizing ids inside the hash and nowhere else. Each
iteration then checks every t-subset containing the new participant.
The negative tests are organized around what each gate is actually for:
- Fault injection flips a bit in one sigma. secshare_gen fails and wipes
its output; the same call with expected_pubshare = NULL SUCCEEDS and
returns a wrong share. That second assertion is the point -- it is the
evidence that the parameter is load-bearing rather than decorative.
Tampered public shares are caught earlier, by
secp256k1_frost_threshold_info_validate, so the test exercises the
recommended flow and not just the module.
- Parameter mismatch, four angles: (a) one helper runs round 1.1 for a
different target and every other helper's share_agg aborts naming it
by identifier; (b) a caller that IGNORES that abort and finishes round
1.2 anyway still cannot produce a usable share, because the
public-share check catches the inconsistent sum -- defence in depth,
not a test of the test's own control flow; (c) the helpers agree with
each other on new_id = 3 while the target expects 4, which round 1.2
cannot see and round 2's own recomputation does; (d) two groups with
identical (t, n, ids, new_id) get different hashes, and a hash from one
fails share_agg in the other.
- Own-slot semantics: filling the caller's own slot of
received_params_hashes32 with garbage changes nothing, because it is
never read -- but the same garbage in a slot that IS read still aborts.
That pair is what makes "recomputation, not string comparison"
testable rather than merely asserted.
- Invalid parameters, including both deliberate divergences: t = 1
refused, enrollment refused at n = 128 while repair at n = 128 is
accepted, n_ids > 128 returning 0 with the output zeroed in a
production build.
Three bugs found while writing these, all in the tests, all worth
naming:
- pubshare_derive takes public shares ALIGNED WITH ids, and the test
helper was handing it the participant-indexed table. Those coincide
exactly when the helper set is 0..u-1, which every test until the
repair case used, so the first non-contiguous helper set {0, 2} was
what exposed it. There is now one helper that does the gather, with a
comment saying which confusion it exists to prevent.
- The fault-injection test compared against r.new_secshare without ever
running round 2, and the mismatch test compared against
r.params_hashes[0] one line before round 1.1 filled it. Both were
reads of uninitialized memory that happened to pass; valgrind found
both.
The randomized test loops COUNT times so -i scales it, following the
iceberg module (tests_impl.h:1322) rather than prefractal's run-once
convention -- a fuzzing loop that ignores the iteration count is not
much of one.
Verification: all twelve tests pass at the default iteration count, at
-i=200 and at -i=2000; ./tests, ./noverify_tests and ./exhaustive_tests
exit 0 with all five FROST-stack modules enabled; the module runs clean
under valgrind (0 errors from 0 contexts); ctime_tests is clean under
valgrind; regenerating vectors.h reproduces it byte for byte.
One note for anyone running these locally: ctime_tests must not be run
against a CPPFLAGS='-DVERIFY' build. secp256k1_scalar_verify branches on
scalar values, which ctime_tests deliberately marks secret, so every
scalar operation in the library reports a finding -- 75997 of them, none
in this module. The CI matrix already pairs -DVERIFY with
CTIMETESTS: 'no' (.github/workflows/ci.yml:119, :596) for this reason.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
libsecp256k1-zkp
A fork of libsecp256k1 with support for advanced and experimental features
Added features:
- Experimental module for ECDSA adaptor signatures.
- Experimental module for ECDSA sign-to-contract.
- Experimental modules for Confidential Assets (Pedersen commitments, range proofs, and surjection proofs).
- Experimental module for address whitelisting.
- Experimental module for Schnorr signature half-aggregation.
- Experimental module for FROST (BIP 445).
- Experimental module for ChillDKG, distributed key generation for FROST (bip-frost-dkg draft).
- Experimental module for Iceberg, a threshold scheme that lets a group of parties stand in for a single MuSig2 (BIP 327) participant.
- Experimental module for Prefractal, a nested FROST+MuSig2 signer that lets a FROST group occupy one participant slot of an ordinary MuSig2 (BIP 327) session.
Experimental features are made available for testing and review by the community. The APIs of these features should not be considered stable.
Build steps
Obtaining and verifying
The git tag for each release (e.g. v0.6.0) is GPG-signed by one of the maintainers.
For a fully verified build of this project, it is recommended to obtain this repository
via git, obtain the GPG keys of the signing maintainer(s), and then verify the release
tag's signature using git.
This can be done with the following steps:
- Obtain the GPG keys listed in SECURITY.md.
- If possible, cross-reference these key IDs with another source controlled by its owner (e.g. social media, personal website). This is to mitigate the unlikely case that incorrect content is being presented by this repository.
- Clone the repository:
git clone https://github.com/bitcoin-core/secp256k1 - Check out the latest release tag, e.g.
git checkout v0.7.1 - Use git to verify the GPG signature:
% git tag -v v0.7.1 | grep -C 3 'Good signature' gpg: Signature made Mon 26 Jan 2026 07:42:46 PM UTC gpg: using RSA key 2840EAABF4BC9F0FFD716AFAFBAFCC46DE2D3FE2 gpg: Good signature from "Pieter Wuille <pieter@wuille.net>" [unknown] gpg: aka "Pieter Wuille <pieter.wuille@gmail.com>" [full] gpg: aka "[jpeg image of size 5996]" [undefined] gpg: WARNING: This key is not certified with a trusted signature! gpg: There is no indication that the signature belongs to the owner. Primary key fingerprint: 133E AC17 9436 F14A 5CF1 B794 860F EB80 4E66 9320 Subkey fingerprint: 2840 EAAB F4BC 9F0F FD71 6AFA FBAF CC46 DE2D 3FE2
Building with Autotools
$ ./autogen.sh # Generate a ./configure script
$ ./configure # Generate a build system
$ make # Run the actual build process
$ make check # Run the test suite
$ sudo make install # Install the library into the system (optional)
To compile optional modules (such as Schnorr signatures), you need to run ./configure with additional flags (such as --enable-module-schnorrsig). Run ./configure --help to see the full list of available flags. For experimental modules, you will also need --enable-experimental as well as a flag for each individual module, e.g. --enable-module-rangeproof.
Building with CMake
To maintain a pristine source tree, CMake encourages to perform an out-of-source build by using a separate dedicated build tree.
Building on POSIX systems
$ cmake -B build # Generate a build system in subdirectory "build"
$ cmake --build build # Run the actual build process
$ ctest --test-dir build # Run the test suite
$ sudo cmake --install build # Install the library into the system (optional)
To compile optional modules (such as Schnorr signatures), you need to run cmake with additional flags (such as -DSECP256K1_ENABLE_MODULE_SCHNORRSIG=ON). Run cmake -B build -LH or ccmake -B build to see the full list of available flags.
Cross compiling
To alleviate issues with cross compiling, preconfigured toolchain files are available in the cmake directory.
For example, to cross compile for Windows:
$ cmake -B build -DCMAKE_TOOLCHAIN_FILE=cmake/x86_64-w64-mingw32.toolchain.cmake
To cross compile for Android with NDK (using NDK's toolchain file, and assuming the ANDROID_NDK_ROOT environment variable has been set):
$ cmake -B build -DCMAKE_TOOLCHAIN_FILE="${ANDROID_NDK_ROOT}/build/cmake/android.toolchain.cmake" -DANDROID_ABI=arm64-v8a -DANDROID_PLATFORM=28
Building on Windows
The following example assumes Visual Studio 2022. Using clang-cl is recommended.
In "Developer Command Prompt for VS 2022":
>cmake -B build -T ClangCL
>cmake --build build --config RelWithDebInfo
Usage examples
Usage examples can be found in the examples directory. To compile them you need to configure with --enable-examples.
- ECDSA example
- Schnorr signatures example
- Deriving a shared secret (ECDH) example
- ElligatorSwift key exchange example
- MuSig2 Schnorr multi-signatures example
To compile the examples, make sure the corresponding modules are enabled.
Benchmark
If configured with --enable-benchmark (which is the default), binaries for benchmarking the libsecp256k1-zkp functions will be present in the root directory after the build.
To print the benchmark result to the command line:
$ ./bench_name
To create a CSV file for the benchmark result :
$ ./bench_name | sed '2d;s/ \{1,\}//g' > bench_name.csv
Reporting a vulnerability
See SECURITY.md
Contributing to libsecp256k1
See CONTRIBUTING.md