Secp256k1.Net 2.0.0

Secp256k1.Net

Cross platform C# wrapper for the native bitcoin-core/secp256k1 C library.

dotnet add package Secp256k1.Net

Platform Support

Pre-compiled binaries are bundled for the following platforms:

This library targets netstandard2.0 and net8.0, supporting a wide-range of .NET deployments: .NET Core 2.0+, .NET Framework 4.6.1+, Mono 5.4+, etc. Conditional compilation is used to enable optimized native library interop features available on modern targets (net8.0 and above).

Quick Start

using Secp256k1Net;
using System.Security.Cryptography;
using System.Text;

// Generate a key pair
var (secretKey, publicKey) = Secp256k1.CreateKeyPair(compressed: true);

// Sign a message (ECDSA)
byte[] message = SHA256.HashData(Encoding.UTF8.GetBytes("Hello, secp256k1!"));
byte[] signature = Secp256k1.Sign(message, secretKey);
bool isValid = Secp256k1.Verify(signature, message, publicKey);

// Schnorr signatures (BIP-340)
var (xOnlyPubKey, _) = Secp256k1.CreateXOnlyPublicKey(secretKey);
byte[] schnorrSig = Secp256k1.SignSchnorr(message, secretKey);
bool schnorrValid = Secp256k1.VerifySchnorr(schnorrSig, message, xOnlyPubKey);

// ECDH shared secret
var (aliceSecret, alicePublic) = Secp256k1.CreateKeyPair(compressed: true);
var (bobSecret, bobPublic) = Secp256k1.CreateKeyPair(compressed: true);
byte[] sharedSecret1 = Secp256k1.ComputeSharedSecret(bobPublic, aliceSecret);
byte[] sharedSecret2 = Secp256k1.ComputeSharedSecret(alicePublic, bobSecret);
// sharedSecret1 == sharedSecret2

See the examples project for more complete working examples.

API Reference

Full API Documentation

The Secp256k1 class exposes static functions that are idiomatic C#, using a thread-safe internal context:

Key Generation & Validation

• CreateSecretKey() - Generate a cryptographically secure random secret key (example)
• CreatePublicKey(secretKey, compressed) - Derive a serialized public key from a secret key (example)
• CreateXOnlyPublicKey(secretKey) - Derive an x-only public key and parity for BIP-340 (example)
• CreateKeyPair(compressed) - Generate a new secret key and public key pair (example)
• IsValidSecretKey(secretKey) - Validate a secret key (example)
• IsValidPublicKey(publicKey) - Validate a serialized public key (example)

Public Key Operations

• CompressPublicKey(publicKey) - Convert a public key to 33-byte compressed format (example)
• DecompressPublicKey(publicKey) - Convert a public key to 65-byte uncompressed format (example)
• NegatePublicKey(publicKey, compressed) - Negate a public key (example)
• CombinePublicKeys(publicKeys, compressed) - Add multiple public keys together (example)

ECDSA Signing & Verification

• Sign(messageHash, secretKey) - Create a 64-byte compact ECDSA signature (example)
• Verify(signature, messageHash, publicKey) - Verify an ECDSA signature (example)
• SignRecoverable(messageHash, secretKey) - Create a recoverable signature with recovery ID (example)
• RecoverPublicKey(signature, recoveryId, messageHash, compressed) - Recover public key from signature (example)

DER Signature Format

• SignatureToDer(compactSignature) - Convert compact signature to DER format (example)
• SignatureFromDer(derSignature) - Convert DER signature to compact format (example)
• VerifyDer(derSignature, messageHash, publicKey) - Verify a DER-encoded signature (example)

Signature Normalization

• NormalizeSignature(signature) - Normalize signature to lower-S form (example)
• IsNormalizedSignature(signature) - Check if signature is in lower-S form (example)

Schnorr Signatures (BIP-340)

• SignSchnorr(messageHash, secretKey, auxRand) - Create a Schnorr signature (example)
• VerifySchnorr(signature, message, publicKey) - Verify a Schnorr signature (example)

ECDH Key Agreement

• ComputeSharedSecret(publicKey, secretKey) - Compute ECDH shared secret (example)

Key Tweaking (BIP-32 HD Wallets)

• TweakSecretKeyAdd(secretKey, tweak) - Add a tweak to a secret key (example)
• TweakPublicKeyAdd(publicKey, tweak, compressed) - Add a tweak to a public key (example)
• TweakSecretKeyMul(secretKey, tweak) - Multiply a secret key by a tweak (example)
• TweakPublicKeyMul(publicKey, tweak, compressed) - Multiply a public key by a tweak (example)
• NegateSecretKey(secretKey) - Negate a secret key (example)

Hashing

• TaggedHash(tag, message) - Compute a BIP-340 tagged hash (example)

Advanced Usage

The Secp256k1 class also provides instance methods that are direct wrappers for the native C library, with near one-to-one API mapping. These offer more control over memory allocation and access to additional features:

• Custom ECDH hash functions - Use custom hash functions for ECDH
• Custom nonce functions - Provide custom nonce generation for signing
• Public key sorting - Sort public keys lexicographically
• Keypair operations - Work with 96-byte keypair objects
• X-only pubkey tweaking - Taproot-style key tweaking (BIP-341)
• ElligatorSwift encoding - BIP-324 encrypted transport
• MuSig2 multi-signatures - Aggregate Schnorr signatures from multiple signers

Benchmarks

Secp256k1.Net is consistently 5-10x faster than the next best library (NBitcoin) and 20-100x faster than pure managed implementations like BouncyCastle, Nethereum, and StarkBank.

BenchmarkDotNet v0.15.8, macOS Sequoia 15.7.1 (24G231) [Darwin 24.6.0]
Apple M3 Max, 1 CPU, 14 logical and 14 physical cores
.NET SDK 10.0.102
  [Host]     : .NET 10.0.2 (10.0.2, 10.0.225.61305), Arm64 RyuJIT armv8.0-a
  DefaultJob : .NET 10.0.2 (10.0.2, 10.0.225.61305), Arm64 RyuJIT armv8.0-a

BenchmarkDotNet v0.15.8, Windows 11 (10.0.26100.7462/24H2/2024Update/HudsonValley) (Hyper-V)
Intel Xeon Platinum 8370C CPU 2.80GHz (Max: 2.79GHz), 1 CPU, 4 logical and 2 physical cores
.NET SDK 10.0.102
  [Host]   : .NET 10.0.2 (10.0.2, 10.0.225.61305), X64 RyuJIT x86-64-v4
  ShortRun : .NET 10.0.2 (10.0.2, 10.0.225.61305), X64 RyuJIT x86-64-v4

Job=ShortRun  IterationCount=3  LaunchCount=1  
WarmupCount=3  

BenchmarkDotNet v0.15.8, Linux Ubuntu 24.04.3 LTS (Noble Numbat)
Intel Xeon Platinum 8370C CPU 2.80GHz (Max: 3.39GHz), 1 CPU, 4 logical and 2 physical cores
.NET SDK 10.0.102
  [Host]   : .NET 10.0.2 (10.0.2, 10.0.225.61305), X64 RyuJIT x86-64-v4
  ShortRun : .NET 10.0.2 (10.0.2, 10.0.225.61305), X64 RyuJIT x86-64-v4

Job=ShortRun  IterationCount=3  LaunchCount=1  
WarmupCount=3