f0014c4c49
Ten tests covering the round trip, the three deliberate deviations from BIP
445, and the failure modes the module cannot catch for its caller.
The centrepiece is a pair of FIXED threshold secret keys, one whose threshold
public key has even Y and one whose has odd Y. The nested equation has no
g_frost factor, and the reason is NOT that the tweak cache is the identity:
stock frost's key-side factor is g*gacc with g = -1 for an odd-Y threshold key
(frost/session_impl.h:664, :797-800), so an implementation that imported
frost's key-side parity works for even-Y groups and fails for odd-Y ones. With
a randomly seeded fixture that is a coin flip per run.
This was verified by mutation rather than assumed. Injecting the pk_odd
negation into prefractal_session_values and rebuilding:
run_prefractal_odd_y_group_key_test FAILED
same test with the even-Y fixture PASSED
so the fixed odd-Y fixture is what makes the trap detectable, and the parity
of the fixture is itself asserted in the test so it cannot quietly stop
testing what it is named after.
The suite:
midstate pins the Prefractal/noncecoef tagged hash against a
freshly initialised one. Nothing else in the tree would
notice a changed b_frost; it would just produce
signatures that do not verify.
e2e the round trip over {2-of-2, 3-of-2, 5-of-3, 4-of-3,
7-of-5} x both lexicographic positions of the group key
x both group-key Y parities x with and without the outer
BIP 341 tweak, against a stock musig cosigner, judged by
secp256k1_schnorrsig_verify on the outer aggregate key.
Both key orders matter because BIP 327 KeyAgg gives the
second distinct key a coefficient of exactly 1.
odd_y_group_key the odd-Y case alone, so a regression names its cause
instead of surfacing as one iteration of that matrix.
partial_sig_verify accepts a good share; rejects a tampered one, the right
share against the wrong member, a share made for a
different signer set (lambda_i is defined over the
participating set), and a different message.
identity_cache a tweaked frost cache is refused by sign, by
partial_sig_verify and by partial_sig_agg, and the same
agg call succeeds with the identity cache, so the
refusal is about the tweak and not the arguments.
key_cache_mismatch thresh_pk and the tweak cache must describe one key.
infinity_nonce both nonce columns can reach infinity independently -
the first is passed through unscaled, the second only
after the b_frost multiplication - and a musig pubnonce
can encode neither, so both are refused; the untouched
set still aggregates.
nonce_reuse the secnonce is wiped, including on calls that then fail
for another reason, so a refused member cannot retry
with the same nonce. Reuse takes the illegal-argument
path via secnonce_load's ARG_CHECK, as stock frost_sign
does, so it is checked with CHECK_ILLEGAL.
negative_control wrong key order and a missing outer tweak both produce
shares that are individually well formed and only fail
at the final BIP 340 verification. These are the
mistakes the module cannot catch for the caller, so the
tests pin where they do surface.
api duplicate identifiers, out-of-range counts, an id
outside the signer set, a share not matching its
pubshare, and NULL pubshares skipping that check as
documented.
Also fixes the outer tweak in the identity-cache test, which declared its
throwaway output as secp256k1_pubkey where frost_pubkey_xonly_tweak_add wants
secp256k1_xonly_pubkey. Both are data[64] so it ran correctly, but it is a
type error and -Wincompatible-pointer-types flags it.
Verified:
cmake ... -DSECP256K1_ENABLE_MODULE_PREFRACTAL=ON -> 10/10 prefractal tests
pass, full suite green
./configure --enable-experimental --enable-module-prefractal && make check
-> 3/3 pass
-Wall -Wextra -Wcast-align -Wshadow -Wundef -std=c89 -pedantic -> no
warnings from any prefractal file
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 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