我已经实现了这段代码，用于使用公钥加密消息并使用私钥解密..现在我需要使用私钥更改它加密并使用公钥解密。我应该在以下代码中更改什么，我是初学者。请帮助。
public static string Encrypt(string plainText, X509Certificate2 certificate)
{
if (string.IsNullOrEmpty(plainText))
throw new ArgumentNullException("plainText");
using (var aesManaged = new AesManaged())
{
aesManaged.KeySize = 256;
aesManaged.BlockSize = 128;
aesManaged.Mode = CipherMode.CBC;
// Create the streams used for encryption.
using (var memoryStream = new MemoryStream())
{
// Generate a Symmetric Key used to actually encrypt the data
RSAPKCS1KeyExchangeFormatter keyFormatter = new RSAPKCS1KeyExchangeFormatter((RSACryptoServiceProvider)certificate.PublicKey.Key);
byte[] keyEncrypted = keyFormatter.CreateKeyExchange(aesManaged.Key, aesManaged.GetType());
//byte[] LenSalt = new byte[_saltSize];
// Create byte arrays to contain
// the length values of the key and IV.
byte[] LenK = new byte[_keyBytes];
byte[] LenIV = new byte[_keyBytes];
// Salt genration :
// default iteration count is 1000 in .NET (this is the same as when using Constructor(string password, int salt))
//using (var keyDerivationFunction = new Rfc2898DeriveBytes(keyEncrypted, LenSalt, _iterations))
//{
// LenSalt = keyDerivationFunction.Salt;
//}
int lKey = keyEncrypted.Length;
LenK = BitConverter.GetBytes(lKey);
int lIV = aesManaged.IV.Length;
LenIV = BitConverter.GetBytes(lIV);
// Write the following to the Stream
// for the encrypted file (outFs):
// - length of the key
// - length of the IV
// - encrypted key
// - the IV
// - the encrypted cipher content
memoryStream.Write(LenK, 0, 4);
memoryStream.Write(LenIV, 0, 4);
//memoryStream.Write(LenSalt, 0, 4);
memoryStream.Write(keyEncrypted, 0, lKey);
memoryStream.Write(aesManaged.IV, 0, lIV);
//memoryStream.Write(LenSalt, 0, _saltSize);
//using (var encryptor = aesManaged.CreateEncryptor(aesManaged.Key, aesManaged.IV))
using (var encryptor = aesManaged.CreateEncryptor())
using (var memoryStreamEnc = new MemoryStream())
{
using (var cryptoStream = new CryptoStream(memoryStreamEnc, encryptor, CryptoStreamMode.Write))
using (var streamWriter = new StreamWriter(cryptoStream))
{
// Send the data through the StreamWriter, through the CryptoStream, to the underlying MemoryStream
streamWriter.Write(plainText);
}
memoryStream.Write(memoryStreamEnc.ToArray(), 0, memoryStreamEnc.ToArray().Length);
}
return Convert.ToBase64String(memoryStream.ToArray());
}
}
}
/// <summary>
/// Decrypts the ciphertext using the public key.
/// </summary>
/// <param name="ciphertext">The ciphertext to decrypt.</param>
/// <param name="certificate">The RSA certificate (need access to Private Key for decryption to work).</param>
/// <returns>The decrypted text.</returns>
public static string Decrypt(string ciphertext, X509Certificate2 certificate)
{
string outstring = string.Empty;
if (string.IsNullOrEmpty(ciphertext))
throw new ArgumentNullException("cipherText");
if (!certificate.HasPrivateKey)
throw new ApplicationException("The private key is not accessible. Decryption is not supported.");
var allTheBytes = Convert.FromBase64String(ciphertext);
//using (var keyDerivationFunction = new Rfc2898DeriveBytes(UTF8Encoding.UTF8.GetString(symmetricKey), saltBytes))
using (var aesManaged = new AesManaged())
{
aesManaged.KeySize = 256;
aesManaged.BlockSize = 128;
aesManaged.Mode = CipherMode.CBC;
// Create byte arrays to get the length of
// the encrypted key and IV.
// These values were stored as 4 bytes each
// at the beginning of the encrypted package.
byte[] LenK = new byte[_keyBytes];
byte[] LenIV = new byte[_keyBytes];
using (MemoryStream InStr = new MemoryStream(allTheBytes))
{
InStr.Seek(0, SeekOrigin.Begin);
InStr.Read(LenK, 0, _keyBytes - 1);
InStr.Seek(_keyBytes, SeekOrigin.Begin);
InStr.Read(LenIV, 0, _keyBytes - 1);
// Convert the lengths to integer values.
int lenK = BitConverter.ToInt32(LenK, 0);
int lenIV = BitConverter.ToInt32(LenIV, 0);
// Determine the start postition of
// the ciphter text (startC)
// and its length(lenC).
int startC = lenK + lenIV + 8;
int lenC = (int)InStr.Length - startC;
// Create the byte arrays for
// the encrypted AesManaged key,
// the IV, and the cipher text.
byte[] KeyEncrypted = new byte[lenK];
byte[] IV = new byte[lenIV];
// Extract the salt, key and IV
// starting from index 8
// after the length values.
InStr.Seek(8, SeekOrigin.Begin);
InStr.Read(KeyEncrypted, 0, lenK);
InStr.Seek(8 + lenK, SeekOrigin.Begin);
InStr.Read(IV, 0, lenIV);
byte[] KeyDecrypted = ((RSACryptoServiceProvider)certificate.PrivateKey).Decrypt(KeyEncrypted, false);
byte[] CipherTextBytes = new byte[lenC];
InStr.Seek(startC, SeekOrigin.Begin);
InStr.Read(CipherTextBytes, 0, lenC);
using (var decryptor = aesManaged.CreateDecryptor(KeyDecrypted, IV))
using (var memoryStream = new MemoryStream(CipherTextBytes))
using (var cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read))
using (var streamReader = new StreamReader(cryptoStream))
{
// Return the decrypted bytes from the decrypting stream.
return streamReader.ReadToEnd();
}
}
}
}