HMACSHA512.Demo.cs

void Main()
{
    { // 0. Create a HMAC 
        byte[] keyHmac = new byte[] { 255 };
        var hmac = new HMACSHA512(keyHmac); // 1st HMACSHA512 ctor
        var result = hmac.ComputeHash(new byte[] { 1, 2, 3 });
        Console.Out.WriteLine($"0. - {Convert.ToBase64String(result)}");
    }

    Console.Out.WriteLine("\r\nThe following MACs should be all equal!\r\n");

    { // 1. Create a HMAC than add a byte to the result and create a second HMAC
        byte[] keyHmac = new byte[] { 255 };
        var hmac = new HMACSHA512(keyHmac); // 1st HMACSHA512 ctor
        var result = hmac.ComputeHash(new byte[] { 1, 2, 3 });
        result = hmac.ComputeHash(result.Concat(new byte[] { 7 }).ToArray());
        Console.Out.WriteLine($"1. - {Convert.ToBase64String(result)}");
    }

    { // 2. Create a HMAC than add a byte to the result and create a second HMAC with a new instance
        byte[] keyHmac = new byte[] { 255 };
        var hmac = new HMACSHA512(keyHmac);  // 1st HMACSHA512 ctor
        var result = hmac.ComputeHash(new byte[] { 1, 2, 3 });
        hmac = new HMACSHA512(keyHmac);  // 2nd HMACSHA512 ctor
        result = hmac.ComputeHash(result.Concat(new byte[] { 7 }).ToArray());
        Console.Out.WriteLine($"2. - {Convert.ToBase64String(result)}");
    }

    { // 3. Create a HMAC from a stream than add a byte to the result and create a second HMAC
        byte[] keyHmac = new byte[] { 255 };
        var hmac = new HMACSHA512(keyHmac);
        using (var resultStream = new MemoryStream())
        {
            using (var hmacStream = new CryptoStream(resultStream, hmac, CryptoStreamMode.Write))
            {
                new MemoryStream(new byte[] { 1, 2, 3 }).CopyTo(hmacStream);
            }
        }

        var result = hmac.Hash;
        result = hmac.ComputeHash(result.Concat(new byte[] { 7 }).ToArray());

        Console.Out.WriteLine($"3. - {Convert.ToBase64String(result)}");
    }


    { // 4. Create a HMAC from a stream than add a byte to the result and create a second HMAC with a new instance
        byte[] keyHmac = new byte[] { 255 };
        var hmac = new HMACSHA512(keyHmac);
        using (var resultStream = new MemoryStream())
        {
			using (var hmacStream = new CryptoStream(resultStream, hmac, CryptoStreamMode.Write))
			{
				new MemoryStream(new byte[] { 1, 2, 3 }).CopyTo(hmacStream);
			}
		}

		var result = hmac.Hash;
		hmac = new HMACSHA512(keyHmac);
		result = hmac.ComputeHash(result.Concat(new byte[] { 7 }).ToArray());

		Console.Out.WriteLine($"4. - {Convert.ToBase64String(result)}");
	}
}

// 0. - J0x6KRHzGh1nTLL+a+pL8H9PJyl1b9/rL7D0j3S1DBpMduct37uMi0mBFEOdkfrLs2Ipn39yoV6GaRoEK+hU7A==
// 
// The following MACs should be all equal!
// 
// 1. - mVd7YQ7AbmRfH57AprAuU1vlSuOucvg+NbUFl7eNurPuvGS/Xrko2Kz3d9vUGXr0P287dOgEKQJDNfMkN2xi5Q==
// 2. - mVd7YQ7AbmRfH57AprAuU1vlSuOucvg+NbUFl7eNurPuvGS/Xrko2Kz3d9vUGXr0P287dOgEKQJDNfMkN2xi5Q==
// 3. - DVncxk/dEYhmmpK5qEnVg0Pc0/MUe8APbAiyZrh+ba35oGv2TGCkFco3gFVZ2gl+h3DpcqP7VbmuthBmCvSKlg==
// 4. - mVd7YQ7AbmRfH57AprAuU1vlSuOucvg+NbUFl7eNurPuvGS/Xrko2Kz3d9vUGXr0P287dOgEKQJDNfMkN2xi5Q==