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

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.