Secp256k1.Net

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.

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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