Get the public key from RSACryptoServiceProvider?
Your logic seems ok and it seems that you only need some sample code.
using System;
using System.Security.Cryptography;
using System.Text;
namespace RSA
{
class Program
{
static void Main(string[] args)
{
try
{
var rsaServer = new RSACryptoServiceProvider(1024);
var publicKeyXml = rsaServer.ToXmlString(false);
var rsaClient = new RSACryptoServiceProvider(1024);
rsaClient.FromXmlString(publicKeyXml);
var data = Encoding.UTF8.GetBytes("Data To Be Encrypted");
var encryptedData = rsaClient.Encrypt(data, false);
var decryptedData = rsaServer.Decrypt(encryptedData, false);
Console.WriteLine(Encoding.UTF8.GetString(decryptedData));
Console.WriteLine("OK");
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
Console.Read();
}
}
}
1 - Please use >= 2048 Bits in your key to be protected til ~2025.
The above is from 2012, but I came across it while trying to create a ssh-rsa key for Putty / Linux server connections.
I've just solved similar problem of creating a public ssh-rsa key in the proper format, to match PuttyGen.
For Microsoft .net RSACryptoServiceProvider it would look like this
RSACryptoServiceProvider RSA = new RSACryptoServiceProvider(3072);
byte[] sshrsa_bytes = Encoding.Default.GetBytes("ssh-rsa");
byte[] n = RSA.ExportParameters(false).Modulus;
byte[] e = RSA.ExportParameters(false).Exponent;
string buffer64;
using (MemoryStream ms = new MemoryStream())
{
ms.Write(ToBytes(sshrsa_bytes.Length), 0, 4);
ms.Write(sshrsa_bytes, 0, sshrsa_bytes.Length);
ms.Write(ToBytes(e.Length), 0, 4);
ms.Write(e, 0, e.Length);
ms.Write(ToBytes(n.Length+1), 0, 4); //Remove the +1 if not Emulating Putty Gen
ms.Write(new byte[] { 0 }, 0, 1); //Add a 0 to Emulate PuttyGen (remove it not emulating)
ms.Write(n, 0, n.Length);
ms.Flush();
buffer64 = Convert.ToBase64String(ms.ToArray());
}
string pubssh = string.Format("ssh-rsa {0} generated-key", buffer64);
You can see my Private Key I used for testing & the putty gen source code link https://www.cameronmoten.com/2017/12/21/rsacryptoserviceprovider-create-a-ssh-rsa-public-key/
I work at Microsoft but this is a personal answer not a Microsoft one.
Original Post for BouncyCastle (Link)