C# Crypto Libraries

C# Crypto Libraries


Cryptography in C# and .NET

  • Bouncy Castle .NET and Nethereum:Hashes, ECC and ECDSA

.NET Cryptography and Bouncy Castle .NET

  • Cryptography in C# and .NET is based on:
  • Nethereum – a simplified library for Ethereum and secp256k1
    • The cryptographic functionality is in Nethereum.Signer
    • Nethereum also includes the Bouncy Castle .NET library

ECDSA in C#: Initialize the Application

Install the "Nethereum.Signer" package from NuGet
dotnet add package Nethereum.Signer
Import the Nethereum Signer namespaces:
using Nethereum.Signer;
using Nethereum.Signer.Crypto;
using Nethereum.Util;
using Nethereum.Hex.HexConvertors.Extensions;
The Bouncy Castle namespaces will also be available, e.g.
Org.BouncyCastle.Math.EC.ECPoint p =;

ECDSA in C#: Generate / Load Keys

// var privKey = EthECKey.GenerateKey(); // Random private key
var privKey = new EthECKey( "97ddae0f3a25b92268175400149d65d6887b9cefaf28ea2c078e05cdc15a3c0a");
byte[] pubKeyCompressed = new ECKey(
privKey.GetPrivateKeyAsBytes(), true).GetPubKey(true);
Console.WriteLine("Private key: {0}",
Console.WriteLine("Public key: {0}",
Console.WriteLine("Public key (compressed): {0}",

ECDSA in C#: Sign Message

string msg = "Message for signing";
byte[] msgBytes = Encoding.UTF8.GetBytes(msg);
byte[] msgHash = new Sha3Keccack().CalculateHash(msgBytes);
var signature = privKey.SignAndCalculateV(msgHash);
Console.WriteLine("Msg: {0}", msg);
Console.WriteLine("Msg hash: {0}", msgHash.ToHex());
Console.WriteLine("Signature: [v = {0}, r = {1}, s = {2}]",
signature.V[0] - 27,

ECDSA in C#: Verify Message

var pubKeyRecovered =
EthECKey.RecoverFromSignature(signature, msgHash);
Console.WriteLine("Recovered pubKey: {0}",
bool validSig = pubKeyRecovered.Verify(msgHash, signature);
Console.WriteLine("Signature valid? {0}", validSig);