c# rsa example
using System;
using System.Security.Cryptography;
namespace RsaCryptoExample
{
static class Program
{
static void Main()
{
//lets take a new CSP with a new 2048 bit rsa key pair
var csp = new RSACryptoServiceProvider(2048);
//how to get the private key
var privKey = csp.ExportParameters(true);
//and the public key ...
var pubKey = csp.ExportParameters(false);
//converting the public key into a string representation
string pubKeyString;
{
//we need some buffer
var sw = new System.IO.StringWriter();
//we need a serializer
var xs = new System.Xml.Serialization.XmlSerializer(typeof(RSAParameters));
//serialize the key into the stream
xs.Serialize(sw, pubKey);
//get the string from the stream
pubKeyString = sw.ToString();
}
//converting it back
{
//get a stream from the string
var sr = new System.IO.StringReader(pubKeyString);
//we need a deserializer
var xs = new System.Xml.Serialization.XmlSerializer(typeof(RSAParameters));
//get the object back from the stream
pubKey = (RSAParameters)xs.Deserialize(sr);
}
//conversion for the private key is no black magic either ... omitted
//we have a public key ... let's get a new csp and load that key
csp = new RSACryptoServiceProvider();
csp.ImportParameters(pubKey);
//we need some data to encrypt
var plainTextData = "foobar";
//for encryption, always handle bytes...
var bytesPlainTextData = System.Text.Encoding.Unicode.GetBytes(plainTextData);
//apply pkcs#1.5 padding and encrypt our data
var bytesCypherText = csp.Encrypt(bytesPlainTextData, false);
//we might want a string representation of our cypher text... base64 will do
var cypherText = Convert.ToBase64String(bytesCypherText);
/*
* some transmission / storage / retrieval
*
* and we want to decrypt our cypherText
*/
//first, get our bytes back from the base64 string ...
bytesCypherText = Convert.FromBase64String(cypherText);
//we want to decrypt, therefore we need a csp and load our private key
csp = new RSACryptoServiceProvider();
csp.ImportParameters(privKey);
//decrypt and strip pkcs#1.5 padding
bytesPlainTextData = csp.Decrypt(bytesCypherText, false);
//get our original plainText back...
plainTextData = System.Text.Encoding.Unicode.GetString(bytesPlainTextData);
}
}
}