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Cross platform C# wrapper for the native secp256k1 lib (netstandard2.0)

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Secp256k1.Net

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Cross platform C# wrapper for the native secp256k1 library.

The nuget package supports win-x64, win-x86, win-arm64, macOS-x64, macOS-arm64 (Apple Silcon), linux-x64, linux-x86, and linux-arm64 out of the box. The native libraries are bundled from the Secp256k1.Native package. This wrapper should work on any other platform that supports netstandard2.0 (.NET Core 2.0+, Mono 5.4+, etc) but requires that the native secp256k1 library be compiled from source.


Example Usage

Generate key pair

using var secp256k1 = new Secp256k1();

// Generate a private key
var privateKey = new byte[Secp256k1.PRIVKEY_LENGTH];
var rnd = System.Security.Cryptography.RandomNumberGenerator.Create();
do { rnd.GetBytes(privateKey); }
while (!secp256k1.SecretKeyVerify(privateKey));

// Derive public key bytes
var publicKey = new byte[Secp256k1.PUBKEY_LENGTH];
Assert.True(secp256k1.PublicKeyCreate(publicKey, privateKey));

// Serialize the public key to compressed format
var serializedCompressedPublicKey = new byte[Secp256k1.SERIALIZED_COMPRESSED_PUBKEY_LENGTH];
Assert.True(secp256k1.PublicKeySerialize(serializedCompressedPublicKey, publicKey, Flags.SECP256K1_EC_COMPRESSED));

// Serialize the public key to uncompressed format
var serializedUncompressedPublicKey = new byte[Secp256k1.SERIALIZED_UNCOMPRESSED_PUBKEY_LENGTH];
Assert.True(secp256k1.PublicKeySerialize(serializedUncompressedPublicKey, publicKey, Flags.SECP256K1_EC_UNCOMPRESSED));

// Parse public key from serialized compressed public key
var parsedPublicKey1 = new byte[Secp256k1.PUBKEY_LENGTH];
Assert.IsTrue(secp256k1.PublicKeyParse(parsedPublicKey1, serializedCompressedPublicKey));
Assert.AreEqual(Convert.ToHexString(publicKey), Convert.ToHexString(parsedPublicKey1));

// Parse public key from serialied uncompressed public key
var parsedPublicKey2 = new byte[Secp256k1.PUBKEY_LENGTH];
Assert.IsTrue(secp256k1.PublicKeyParse(parsedPublicKey2, serializedUncompressedPublicKey));
Assert.AreEqual(Convert.ToHexString(publicKey), Convert.ToHexString(parsedPublicKey2));

Sign and verify message

using var secp256k1 = new Secp256k1();
var keypair = new
{
    PrivateKey = Convert.FromHexString("7ef7543476bf146020cb59f9968a25ec67c3c73dbebad8a0b53a3256170dcdfe"),
    PublicKey = Convert.FromHexString("2208d5dc41d4f3ed555aff761e9bb0b99fbe6d1503b98711944be6a362242ebfa1c788c7a4e13f6aaa4099f9d2175fc031e5aa3ba08eb280e87dfb43bdae207f")
};

// Create message hash
var msgBytes = System.Text.Encoding.UTF8.GetBytes("Hello!!");
var msgHash = System.Security.Cryptography.SHA256.HashData(msgBytes);
Assert.Equal(Secp256k1.HASH_LENGTH, msgHash.Length);

// Sign then verify message hash
var signature = new byte[Secp256k1.SIGNATURE_LENGTH];
Assert.True(secp256k1.Sign(signature, msgHash, keypair.PrivateKey));
Assert.True(secp256k1.Verify(signature, msgHash, keypair.PublicKey));

Compute an ECDH (EC Diffie-Hellman) secret

using var secp256k1 = new Secp256k1();
            
var aliceKeyPair = new
{
  PrivateKey = Convert.FromHexString("7ef7543476bf146020cb59f9968a25ec67c3c73dbebad8a0b53a3256170dcdfe"),
  PublicKey = Convert.FromHexString("2208d5dc41d4f3ed555aff761e9bb0b99fbe6d1503b98711944be6a362242ebfa1c788c7a4e13f6aaa4099f9d2175fc031e5aa3ba08eb280e87dfb43bdae207f")
};
var bobKeyPair = new
{
  PrivateKey = Convert.FromHexString("d8bdb07407bb011137ef7ba6a7f07c6a55c1e3600a6aa138e34ab5c16439ceda"),
  PublicKey = Convert.FromHexString("62127c4563f711169b1d3e56a34f218302a2587c3725bd418b9388933373e095d45ec4d74ca734599598c89d7719bda5fb799afeec89c6940d569e05bd5a1bba")
};

// Create secret using Alice's public key and Bob's private key
var secret1 = new byte[Secp256k1.SECRET_LENGTH];
Assert.True(secp256k1.Ecdh(secret1, aliceKeyPair.PublicKey, bobKeyPair.PrivateKey));

// Create secret using Bob's public key and Alice's private key
var secret2 = new byte[Secp256k1.SECRET_LENGTH];
Assert.True(secp256k1.Ecdh(secret2, bobKeyPair.PublicKey, aliceKeyPair.PrivateKey));

// Validate secrets match
Assert.Equal(Convert.ToHexString(secret1), Convert.ToHexString(secret2));

Parsing and serializing DER signatures

using var secp256k1 = new Secp256k1();

// Parse DER signature
var signatureOutput = new byte[Secp256k1.SIGNATURE_LENGTH];
var derSignature = Convert.FromHexString("30440220484ECE2B365D2B2C2EAD34B518328BBFEF0F4409349EEEC9CB19837B5795A5F5022040C4F6901FE489F923C49D4104554FD08595EAF864137F87DADDD0E3619B0605");                
Assert.True(secp256k1.SignatureParseDer(signatureOutput, derSignature));

// Serialize DER signature
Span<byte> derSignatureOutput = new byte[Secp256k1.SERIALIZED_DER_SIGNATURE_MAX_SIZE];
Assert.True(secp256k1.SignatureSerializeDer(derSignatureOutput, signatureOutput, out int signatureOutputLength));
derSignatureOutput = derSignatureOutput.Slice(0, signatureOutputLength);

// Validate signature is the same after round trip parse and serialize
Assert.Equal(Convert.ToHexString(derSignature), Convert.ToHexString(derSignatureOutput));

See the tests project for more examples.

Benchmarks

BenchmarkDotNet=v0.13.4, OS=macOS Monterey 12.6.2 (21G320) [Darwin 21.6.0]
Apple M1 Pro, 1 CPU, 10 logical and 10 physical cores
.NET SDK=7.0.102
  [Host]     : .NET 7.0.2 (7.0.222.60605), Arm64 RyuJIT AdvSIMD
  DefaultJob : .NET 7.0.2 (7.0.222.60605), Arm64 RyuJIT AdvSIMD

Method feature Mean Error StdDev Ratio RatioSD
Secp256k1Net SignOnly 53.00 μs 0.044 μs 0.037 μs 1.00 0.00
Nbitcoin SignOnly 186.25 μs 0.255 μs 0.226 μs 3.51 0.01
Nethereum SignOnly 579.06 μs 1.272 μs 0.993 μs 10.93 0.02
BouncyCastle SignOnly 582.83 μs 6.968 μs 5.818 μs 11.00 0.11
Chainers SignOnly 778.34 μs 15.176 μs 14.905 μs 14.72 0.30
StarkBank SignOnly 1,800.91 μs 4.751 μs 4.444 μs 34.00 0.10
Secp256k1Net SignAndVerify 90.97 μs 0.084 μs 0.075 μs 1.00 0.00
Nbitcoin SignAndVerify 373.22 μs 1.822 μs 1.521 μs 4.10 0.02
Nethereum SignAndVerify 1,679.02 μs 3.984 μs 3.327 μs 18.46 0.04
BouncyCastle SignAndVerify 1,701.31 μs 18.157 μs 16.985 μs 18.72 0.18
StarkBank SignAndVerify 5,315.49 μs 15.796 μs 14.002 μs 58.43 0.15

BenchmarkDotNet=v0.13.4, OS=macOS Monterey 12.6.3 (21G419) [Darwin 21.6.0]
Intel Xeon CPU E5-1650 v2 3.50GHz (Max: 3.34GHz), 1 CPU, 3 logical and 3 physical cores
.NET SDK=7.0.102
  [Host]     : .NET 7.0.2 (7.0.222.60605), X64 RyuJIT AVX
  DefaultJob : .NET 7.0.2 (7.0.222.60605), X64 RyuJIT AVX

Method feature Mean Error StdDev Median Ratio RatioSD
Secp256k1Net SignOnly 97.17 μs 4.112 μs 11.666 μs 93.27 μs 1.00 0.00
Nbitcoin SignOnly 362.74 μs 15.863 μs 45.769 μs 357.29 μs 3.79 0.65
Nethereum SignOnly 1,122.70 μs 28.246 μs 78.740 μs 1,098.21 μs 11.71 1.46
BouncyCastle SignOnly 1,079.60 μs 21.453 μs 43.823 μs 1,067.88 μs 11.18 1.36
Chainers SignOnly 1,300.33 μs 23.165 μs 30.121 μs 1,301.86 μs 12.49 1.65
StarkBank SignOnly 2,564.26 μs 41.055 μs 40.322 μs 2,566.36 μs 25.16 2.97
Secp256k1Net SignAndVerify 146.25 μs 2.679 μs 2.506 μs 145.54 μs 1.00 0.00
Nbitcoin SignAndVerify 724.20 μs 7.401 μs 6.561 μs 723.84 μs 4.95 0.09
Nethereum SignAndVerify 3,048.38 μs 59.507 μs 55.663 μs 3,058.23 μs 20.85 0.57
BouncyCastle SignAndVerify 2,997.17 μs 51.521 μs 45.672 μs 2,999.00 μs 20.48 0.41
StarkBank SignAndVerify 8,008.58 μs 159.859 μs 304.149 μs 8,022.61 μs 53.30 2.05

BenchmarkDotNet=v0.13.4, OS=ubuntu 22.04
Intel Xeon Platinum 8370C CPU 2.80GHz, 1 CPU, 2 logical and 2 physical cores
.NET SDK=7.0.102
  [Host]     : .NET 7.0.2 (7.0.222.60605), X64 RyuJIT AVX2
  DefaultJob : .NET 7.0.2 (7.0.222.60605), X64 RyuJIT AVX2

Method feature Mean Error StdDev Ratio RatioSD
Secp256k1Net SignOnly 88.61 μs 0.047 μs 0.041 μs 1.00 0.00
Nbitcoin SignOnly 303.01 μs 0.478 μs 0.447 μs 3.42 0.01
Nethereum SignOnly 988.51 μs 4.649 μs 4.348 μs 11.16 0.05
BouncyCastle SignOnly 1,005.06 μs 4.370 μs 4.087 μs 11.35 0.05
Chainers SignOnly 1,545.85 μs 29.765 μs 29.233 μs 17.42 0.35
StarkBank SignOnly 2,441.18 μs 5.709 μs 5.340 μs 27.55 0.06
Secp256k1Net SignAndVerify 146.08 μs 0.047 μs 0.039 μs 1.00 0.00
Nbitcoin SignAndVerify 631.46 μs 0.782 μs 0.693 μs 4.32 0.01
Nethereum SignAndVerify 2,800.69 μs 19.084 μs 17.851 μs 19.17 0.13
BouncyCastle SignAndVerify 2,878.09 μs 16.666 μs 14.774 μs 19.71 0.10
StarkBank SignAndVerify 7,121.17 μs 13.625 μs 12.745 μs 48.77 0.08

BenchmarkDotNet=v0.13.4, OS=Windows 10 (10.0.20348.1487), VM=Hyper-V
Intel Xeon CPU E5-2673 v4 2.30GHz, 1 CPU, 2 logical and 2 physical cores
.NET SDK=7.0.102
  [Host]     : .NET 7.0.2 (7.0.222.60605), X64 RyuJIT AVX2
  DefaultJob : .NET 7.0.2 (7.0.222.60605), X64 RyuJIT AVX2

Method feature Mean Error StdDev Ratio RatioSD
Secp256k1Net SignOnly 165.8 μs 3.28 μs 3.07 μs 1.00 0.00
Nbitcoin SignOnly 374.1 μs 7.43 μs 8.84 μs 2.25 0.06
Nethereum SignOnly 1,206.2 μs 20.57 μs 20.21 μs 7.28 0.21
BouncyCastle SignOnly 1,200.1 μs 20.21 μs 18.91 μs 7.24 0.17
Chainers SignOnly 1,613.4 μs 31.76 μs 50.38 μs 9.78 0.31
StarkBank SignOnly 3,341.0 μs 63.47 μs 73.09 μs 20.17 0.57
Secp256k1Net SignAndVerify 274.4 μs 5.30 μs 7.26 μs 1.00 0.00
Nbitcoin SignAndVerify 807.3 μs 16.02 μs 32.00 μs 3.00 0.16
Nethereum SignAndVerify 3,490.7 μs 68.01 μs 101.79 μs 12.74 0.47
BouncyCastle SignAndVerify 3,438.9 μs 68.07 μs 109.93 μs 12.52 0.52
StarkBank SignAndVerify 9,331.1 μs 184.57 μs 318.37 μs 34.38 1.49

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Cross platform C# wrapper for the native secp256k1 lib (netstandard2.0)

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