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Books / Practical Cryptography for Developers (Unfinished) / Chapter 10
C# Crypto Libraries
C# Crypto Libraries
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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:
- The build-in libraries: System.Security.Cryptography
- The Bouncy Castle .NET– a powerful C# cryptography library
- Nethereum – a simplified library for Ethereum and secp256k1
- Nethereum – https://github.com/Nethereum
- 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}",
privKey.GetPrivateKey().Substring(4));
Console.WriteLine("Public key: {0}",
privKey.GetPubKey().ToHex().Substring(2));
Console.WriteLine("Public key (compressed): {0}",
pubKeyCompressed.ToHex());
Complete example:https://gist.github.com/nakov/f2a579eb9893b29338b11e063d6f80c2
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,
signature.R.ToHex(),
signature.S.ToHex());
Complete example:https://gist.github.com/nakov/f2a579eb9893b29338b11e063d6f80c2
ECDSA in C#: Verify Message
var pubKeyRecovered =
EthECKey.RecoverFromSignature(signature, msgHash);
Console.WriteLine("Recovered pubKey: {0}",
pubKeyRecovered.GetPubKey().ToHex().Substring(2));
bool validSig = pubKeyRecovered.Verify(msgHash, signature);
Console.WriteLine("Signature valid? {0}", validSig);
Complete example:https://gist.github.com/nakov/f2a579eb9893b29338b11e063d6f80c2