代碼示例如下（來自MSDN）：
using System;
using System.Security.Cryptography;
using System.IO;
using System.Text;
namespace Microsoft.Samples.Security.PublicKey
{
class App
{
// Main entry point
static void Main(string[] args)
{
// Instantiate 3 People for example. See the Person class below
Person alice = new Person("Alice");
Person bob = new Person("Bob");
Person steve = new Person("Steve");
// Messages that will Exchanged. See CipherMessage class below
CipherMessage aliceMessage;
CipherMessage bobMessage;
CipherMessage steveMessage;
// Example of encrypting/decrypting your own message
Console.WriteLine("Encrypting/Decrypting Your Own Message");
Console.WriteLine("-----------------------------------------");
// Alice encrypts a message using her own public key
aliceMessage = alice.EncryptMessage("Alice wrote this message");
// then using her private key can decrypt the message
alice.DecryptMessage(aliceMessage);
// Example of Exchanging Keys and Messages
Console.WriteLine();
Console.WriteLine("Exchanging Keys and Messages");
Console.WriteLine("-----------------------------------------");
// Alice Sends a copy of her public key to Bob and Steve
bob.GetPublicKey(alice);
steve.GetPublicKey(alice);
// Bob and Steve both encrypt messages to send to Alice
bobMessage = bob.EncryptMessage("Hi Alice! - Bob.");
steveMessage = steve.EncryptMessage("How are you? - Steve");
// Alice can decrypt and read both messages
alice.DecryptMessage(bobMessage);
alice.DecryptMessage(steveMessage);
Console.WriteLine();
Console.WriteLine("Private Key required to read the messages");
Console.WriteLine("-----------------------------------------");
// Steve cannot read the message that Bob encrypted
steve.DecryptMessage(bobMessage);
// Not even Bob can use the Message he encrypted for Alice.
// The RSA private key is required to decrypt the RS2 key used
// in the decryption.
bob.DecryptMessage(bobMessage);
} // method Main
} // class App
class CipherMessage
{
public byte[] cipherBytes; // RC2 encrypted message text
public byte[] rc2Key; // RSA encrypted rc2 key
public byte[] rc2IV; // RC2 initialization vector
}
class Person
{
private RSACryptoServiceProvider rsa;
private RC2CryptoServiceProvider rc2;
private string name;
// Maximum key size for the RC2 algorithm
const int keySize = 128;
// Person constructor
public Person(string p_Name)
{
rsa = new RSACryptoServiceProvider();
rc2 = new RC2CryptoServiceProvider();
rc2.KeySize = keySize;
name = p_Name;
}
// Used to send the rsa public key parameters
public RSAParameters SendPublicKey()
{
RSAParameters result = new RSAParameters();
try
{
result = rsa.ExportParameters(false);
}
catch (CryptographicException e)
{
Console.WriteLine(e.Message);
}
return result;
}
// Used to import the rsa public key parameters
public void GetPublicKey(Person receiver)
{
try
{
rsa.ImportParameters(receiver.SendPublicKey());
}
catch (CryptographicException e)
{
Console.WriteLine(e.Message);
}
}
public CipherMessage EncryptMessage(string text)
{
// Convert string to a byte array
CipherMessage message = new CipherMessage();
byte[] plainBytes = Encoding.Unicode.GetBytes(text.ToCharArray());
// A new key and iv are generated for every message
rc2.GenerateKey();
rc2.GenerateIV();
// The rc2 initialization doesnt need to be encrypted, but will
// be used in conjunction with the key to decrypt the message.
message.rc2IV = rc2.IV;
try
{
// Encrypt the RC2 key using RSA encryption
message.rc2Key = rsa.Encrypt(rc2.Key, false);
}
catch (CryptographicException e)
{
// The High Encryption Pack is required to run this sample
// because we are using a 128-bit key. See the readme for
// additional information.
Console.WriteLine("Encryption Failed. Ensure that the" +
" High Encryption Pack is installed.");
Console.WriteLine("Error Message: " + e.Message);
Environment.Exit(0);
}
// Encrypt the Text Message using RC2 (Symmetric algorithm)
ICryptoTransform sse = rc2.CreateEncryptor();
MemoryStream ms = new MemoryStream();
CryptoStream cs = new CryptoStream(ms, sse, CryptoStreamMode.Write);
try
{
cs.Write(plainBytes, 0, plainBytes.Length);
cs.FlushFinalBlock();
message.cipherBytes = ms.ToArray();
}
catch (Exception e)
{
Console.WriteLine(e.Message);
}
finally
{
ms.Close();
cs.Close();
}
return message;
} // method EncryptMessage
public void DecryptMessage(CipherMessage message)
{
// Get the RC2 Key and Initialization Vector
rc2.IV = message.rc2IV;
try
{
// Try decrypting the rc2 key
rc2.Key = rsa.Decrypt(message.rc2Key, false);
}
catch (CryptographicException e)
{
Console.WriteLine("Decryption Failed: " + e.Message);
return;
}
ICryptoTransform ssd = rc2.CreateDecryptor();
// Put the encrypted message in a memorystream
MemoryStream ms = new MemoryStream(message.cipherBytes);
// the CryptoStream will read cipher text from the MemoryStream
CryptoStream cs = new CryptoStream(ms, ssd, CryptoStreamMode.Read);
byte[] initialText = new Byte[message.cipherBytes.Length];
try
{
// Decrypt the message and store in byte array
cs.Read(initialText, 0, initialText.Length);
}
catch (Exception e)
{
Console.WriteLine(e.Message);
}
finally
{
ms.Close();
cs.Close();
}
// Display the message received
Console.WriteLine(name + " received the following message:");
Console.WriteLine(" " + Encoding.Unicode.GetString(initialText));
} // method DecryptMessage
} // class Person
} // namespace PublicKey
