5155ee03f7
Fifth of six commits. examples/frost_enrollment.c runs a 2-of-3 group
through an enrollment to 2-of-4, signs with the new participant, and then
repairs a lost share -- all roles in one process, following
examples/frost.c's structure.
The example exists mostly to demonstrate two things the API cannot
enforce and that a reader would otherwise have to reconstruct from the
documentation.
First, the verification flow, in the order that makes it non-circular:
1. obtain thresh_pk from a source authenticated INDEPENDENTLY of the
helpers (here, the dealer step, commented as the stand-in);
2. validate the helpers' public shares against it with
secp256k1_frost_threshold_info_validate;
3. derive the expected public share from those validated shares;
4. only then run round 2, passing the same authenticated thresh_pk.
Skip step 1 or 2 and every check in round 2 still passes -- on a share
from whatever polynomial t colluding helpers chose to present. The
example says so at the point where it would be tempting to skip them.
Second, the authorization gap. There is no authorization step in the
protocol: anyone who convinces t helpers to run it receives a valid
share, and in repair mode that is an existing participant's actual
share. The precondition sits in the comment on enroll(), where a reader
copying the function will see it, and again at the repair call site,
which is where it bites hardest.
Beyond that the example is a working reference for the parts that are
fiddly to get right from the header alone: the transposition between
round 1.1's output buffers and round 1.2's input buffer (helper j
collects entry j of every helper's buffer), the opposite own-slot
conventions of the two round-1.2 buffers, the n -> n+1 bookkeeping with
threshold_info_validate over the extended table, and the fact that the
resulting signature verifies against the group's ORIGINAL threshold
public key, since enrollment changes neither the polynomial nor any
existing share.
The repair half asserts byte equality with the original secret share and
the original public share, so a regression there fails the example rather
than passing quietly.
Wired into both build systems next to the iceberg example: Makefile.am
(noinst_PROGRAMS and TESTS under ENABLE_MODULE_FROST_ENROLLMENT) and
examples/CMakeLists.txt. The .gitignore entry landed with the Phase 1
scaffolding.
Verification. Autotools: builds warning-free and `make check` reports
12/12 PASS including frost_enrollment_example; five consecutive runs exit
0 (the key material is freshly random each time, so this exercises both
threshold-key parities in practice). CMake: with
-DSECP256K1_BUILD_EXAMPLES=ON, ctest runs all nine examples and
secp256k1.example.frost_enrollment passes; the full ctest suite is
523/523 with frost, chilldkg, iceberg, prefractal and frost-enrollment
all enabled. The source is clean under gcc -std=c89 -pedantic -Wall
-Wextra.
Note for anyone reproducing this: examples are OFF by default in both
build systems (--enable-examples for autotools,
-DSECP256K1_BUILD_EXAMPLES=ON for CMake), so a plain build will not
compile this file at all.
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