Kgothatso Ngako 3765a82886 frost: document deterministic_sign's nonce derivation domain
BIP 445's det_nonce_hash commits to the secret share, my_id, u, the
sorted ids, the aggothernonce, the x-only tweaked threshold public key
and the message. It does not commit to the pubshares, to the untweaked
threshold public key, or to the accumulated tweaks. Because Q and -Q
share an x-coordinate, two tweak caches can agree on everything the
derivation hashes and still disagree on the sign g*gacc that multiplies
the secret share -- a cache initialized from thresh_pk and one
initialized from its negation being the smallest example.

Two calls differing only in that emit the same pubnonce and partial
signatures s = k + e*lambda*d and s' = k - e*lambda*d over the identical
k = k1 + b*k2, so subtracting them yields the secret share. Demonstrated
on a sole signer (u = 1, ids = {0}, pubshares = NULL) with thresh_sk =
0x11.. and msg = 0x42..:

  tweaked pk (cache A)  4f355bdc...075871aa
  tweaked pk (cache B)  4f355bdc...075871aa   same x-only key
  pubnonce A == pubnonce B                    nonce reused
  sA - sB               0d7d9c4e...aa748ffa
  -2*e*d                0d7d9c4e...aa748ffa   d recovered

Nothing inside a single call can catch this. The self-verification that
Sign performs passes in both cases, because each partial signature is
individually valid under the cache it was produced with;
validate_session_params likewise only ties the pubshares to the cache's
own Q0, which both caches satisfy by construction. Note also that
pubshares is optional, so there need not be a second value to disagree
with.

No code change: this is the specified derivation, and committing to Q0
or to gacc here would diverge from BIP 445 and invalidate the
det_sign test vectors. The obligation is the caller's, so state it where
the caller will meet it -- in the function's own documentation and
alongside the existing secnonce and session_secrand32 rules in frost.md.
The rule is that the tweak cache and the pubshares are fixed key
material settled at key generation, never per-session parameters taken
from a coordinator or a peer; under that discipline a repeated call is
byte-identical and harmless, which is the point of a deterministic
nonce.

Worth raising against the BIP: the spec could close this by hashing the
untweaked threshold public key, at the cost of new test vectors.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-09-01 23:37:22 +02:00
2026-08-31 12:25:55 +02:00
2026-08-31 12:25:55 +02:00
2026-08-31 12:25:09 +02:00
2013-05-09 15:24:32 +02:00

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 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:

  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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