using System.Security.Cryptography;
using System.Text;




// ---- Hashing example
var data = "My Passwort";

HashAlgorithm sha = SHA256.Create();
byte[] result = sha.ComputeHash(Encoding.ASCII.GetBytes(data));

foreach(var byt in result)
{
    Console.Write($"{byt:X}");
}
// ----

// ---- Signing

/*
Verifying a digital signature is the opposite of signing data. 
Verifying a signature will tell you if the signed data has changed 
or not. When a digital signature is verified, the signature is decrypted 
using the public key to produce the original hash value. The data that was 
signed is hashed. If the two hash values match, then the signature has been 
verified. To do this, write a program.


publicKey kann verschlüssen. Nur der privat key kann aber Entschlüssen.

*/


// https://learn.microsoft.com/en-us/dotnet/standard/security/cryptographic-signatures
using SHA256 alg = SHA256.Create();

byte[] data = Encoding.ASCII.GetBytes("Hello, from the .NET Docs!");
byte[] hash = alg.ComputeHash(data);
RSAParameters sharedParameters;
byte[] signedHash;

// Generate signature
using (RSA rsa = RSA.Create())
{
    sharedParameters = rsa.ExportParameters(false); //Public key

    RSAPKCS1SignatureFormatter rsaFormatter = new(rsa);
    rsaFormatter.SetHashAlgorithm(nameof(SHA256));

    signedHash = rsaFormatter.CreateSignature(hash);
}

// Verify signature
using (RSA rsa = RSA.Create())
{
    rsa.ImportParameters(sharedParameters); //Public key

    RSAPKCS1SignatureDeformatter rsaDeformatter = new(rsa);
    rsaDeformatter.SetHashAlgorithm(nameof(SHA256));

    if (rsaDeformatter.VerifySignature(hash, signedHash))
    {
        Console.WriteLine("The signature is valid.");
    }
    else
    {
        Console.WriteLine("The signature is not valid.");
    }
}


// ----