Kgothatso Ngako 5409aae813 chilldkg: Phase 4 - public coordinator API
Add the coordinator side of the ChillDKG protocol
(bip-frost-dkg v0.3.0-dev, reference commit
a91896883f85b159415ecf298d5e844879af112d), as thin wrappers over the
Phase 2 encpedpop coordinator internals (whose cmsg1 output was
already verified byte-identical to the reference coordinator_step1).

Public API:
- secp256k1_chilldkg_coordinator_step1: takes an array of pointers to
  the n participant pmsg1 messages (musig/frost-style convention),
  parses each with checked scalar parse, aggregates SimplPedPop and
  EncPedPop, builds eq_input (including the enc_secshares suffix,
  mirroring the reference) and emits cmsg1 (162n + 33(t-1) bytes).
  PoPs are not verified coordinator-side, exactly as the reference.
- secp256k1_chilldkg_coordinator_finalize: concatenates the n CertEq
  pmsg2 signatures into the 64n-byte certificate, verifies all of them
  via certeq_verify (hostpubkeys recovered from eq_input at offset
  4+33t), and outputs the coordinator-side DKG result: threshold
  pubkey, pubshares and recovery data -- no secshare.
- secp256k1_chilldkg_coordinator_state: opaque, 21041 bytes,
  magic-validated, holds only t, n, eq_input, thresh_pk and pubshares
  -- no secret material, documented as freely copyable/persistable so
  a stateless coordinator is possible.

Blame mapping (verified against chilldkg.py):
- malformed pmsg1 (bad commitment encoding, overflowing encrypted
  share) -> FAULTY_PARTICIPANT(sender index),
- invalid CertEq signature -> FAULTY_PARTICIPANT(failing index)
  (deliberately different from participant_finalize, which maps the
  same failure to FAULTY_COORDINATOR -- matching the reference),
- invalid session params -> INVALID_INPUT; all outputs zeroed on
  failure.

tests_impl.h: chilldkg_coordinator_api_test runs a full n=3,t=2
session through only the public APIs on both sides, byte-exact
against the Python reference vectors and cross-checked against every
participant's finalize outputs; blame cases (malformed pmsg1 and
overflowing share -> FAULTY_PARTICIPANT with the right index, bad
CertEq sig -> FAULTY_PARTICIPANT(2), zeroed outputs); misuse coverage
(NULL args, corrupted state magic).

Verified: make check 3/3 (incl. noverify); CMake ctest 365/365;
./tests --target=chilldkg green.
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libsecp256k1-zkp

Dependencies: None

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 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:

  1. Obtain the GPG keys listed in SECURITY.md.
  2. 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.
  3. Clone the repository:
    git clone https://github.com/bitcoin-core/secp256k1
    
  4. Check out the latest release tag, e.g.
    git checkout v0.7.1
    
  5. 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.

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

Description
Experimental fork of libsecp256k1 with support for pedersen commitments and range proofs.
Readme 15 MiB
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