public class EncrypHelp
{
static public byte[] RSAEncrypt(byte[] DataToEncrypt, RSAParameters RSAKeyInfo, bool DoOAEPPadding)
{
try
{
byte[] encryptedData;
//Create a new instance of RSACryptoServiceProvider.
using (RSACryptoServiceProvider RSA = new RSACryptoServiceProvider())
{ //Import the RSA Key information. This only needs
//toinclude the public key information.
RSA.ImportParameters(RSAKeyInfo); //Encrypt the passed byte array and specify OAEP padding.
//OAEP padding is only available on Microsoft Windows XP or
//later.
encryptedData = RSA.Encrypt(DataToEncrypt, DoOAEPPadding);
}
return encryptedData;
}
//Catch and display a CryptographicException
//to the console.
catch (CryptographicException e)
{
Console.WriteLine(e.Message); return null;
} } static public byte[] RSADecrypt(byte[] DataToDecrypt, RSAParameters RSAKeyInfo, bool DoOAEPPadding)
{
try
{
byte[] decryptedData;
//Create a new instance of RSACryptoServiceProvider.
using (RSACryptoServiceProvider RSA = new RSACryptoServiceProvider())
{
//Import the RSA Key information. This needs
//to include the private key information.
RSA.ImportParameters(RSAKeyInfo); //Decrypt the passed byte array and specify OAEP padding.
//OAEP padding is only available on Microsoft Windows XP or
//later.
decryptedData = RSA.Decrypt(DataToDecrypt, DoOAEPPadding);
}
return decryptedData;
}
//Catch and display a CryptographicException
//to the console.
catch (CryptographicException e)
{
Console.WriteLine(e.ToString()); return null;
} } public static String Encrypt(String plaintext, X509Certificate2 pubcrt)
{
X509Certificate2 _X509Certificate2 = pubcrt;
using (RSACryptoServiceProvider RSACryptography = _X509Certificate2.PublicKey.Key as RSACryptoServiceProvider)
{
Byte[] PlaintextData = Encoding.UTF8.GetBytes(plaintext);
int MaxBlockSize = RSACryptography.KeySize / 8 - 11; //加密块最大长度限制 if (PlaintextData.Length <= MaxBlockSize)
return Convert.ToBase64String(RSACryptography.Encrypt(PlaintextData, false)); using (MemoryStream PlaiStream = new MemoryStream(PlaintextData))
using (MemoryStream CrypStream = new MemoryStream())
{
Byte[] Buffer = new Byte[MaxBlockSize];
int BlockSize = PlaiStream.Read(Buffer, 0, MaxBlockSize); while (BlockSize > 0)
{
Byte[] ToEncrypt = new Byte[BlockSize];
Array.Copy(Buffer, 0, ToEncrypt, 0, BlockSize); Byte[] Cryptograph = RSACryptography.Encrypt(ToEncrypt, false);
CrypStream.Write(Cryptograph, 0, Cryptograph.Length); BlockSize = PlaiStream.Read(Buffer, 0, MaxBlockSize);
} return Convert.ToBase64String(CrypStream.ToArray(), Base64FormattingOptions.None);
}
}
} public static String Decrypt(String ciphertext, X509Certificate2 prvpfx)
{
X509Certificate2 _X509Certificate2 = prvpfx;
using (RSACryptoServiceProvider RSACryptography = _X509Certificate2.PrivateKey as RSACryptoServiceProvider)
{
Byte[] CiphertextData = Convert.FromBase64String(ciphertext);
int MaxBlockSize = RSACryptography.KeySize / 8; //解密块最大长度限制 if (CiphertextData.Length <= MaxBlockSize)
return Encoding.UTF8.GetString(RSACryptography.Decrypt(CiphertextData, false)); using (MemoryStream CrypStream = new MemoryStream(CiphertextData))
using (MemoryStream PlaiStream = new MemoryStream())
{
Byte[] Buffer = new Byte[MaxBlockSize];
int BlockSize = CrypStream.Read(Buffer, 0, MaxBlockSize); while (BlockSize > 0)
{
Byte[] ToDecrypt = new Byte[BlockSize];
Array.Copy(Buffer, 0, ToDecrypt, 0, BlockSize); Byte[] Plaintext = RSACryptography.Decrypt(ToDecrypt, false);
PlaiStream.Write(Plaintext, 0, Plaintext.Length); BlockSize = CrypStream.Read(Buffer, 0, MaxBlockSize);
} return Encoding.UTF8.GetString(PlaiStream.ToArray());
}
}
} private static X509Certificate2 RetrieveX509Certificate()
{
return null; //检索用于 RSA 加密的 X509Certificate2 证书
} //调用方法 public void doit()
{ //Create a UnicodeEncoder to convert between byte array and string.
UnicodeEncoding ByteConverter = new UnicodeEncoding(); //Create byte arrays to hold original, encrypted, and decrypted data.
byte[] dataToEncrypt = ByteConverter.GetBytes("310991");
byte[] encryptedData;
byte[] decryptedData; X509Certificate2 pubcrt = new X509Certificate2(AppDomain.CurrentDomain.BaseDirectory + "cmb.cer");
RSACryptoServiceProvider pubkey = (RSACryptoServiceProvider)pubcrt.PublicKey.Key;
//X509Certificate2 prvcrt = new X509Certificate2(AppDomain.CurrentDomain.BaseDirectory + "bfkey.pfx", "123456789", X509KeyStorageFlags.Exportable);
//RSACryptoServiceProvider prvkey = (RSACryptoServiceProvider)prvcrt.PrivateKey; encryptedData = EncrypHelp.RSAEncrypt(dataToEncrypt, pubkey.ExportParameters(false), false);
string encryptedDataStr = Convert.ToBase64String(encryptedData);
Console.WriteLine("Encrypted plaintext: {0}", Convert.ToBase64String(encryptedData)); //decryptedData = EncrypHelp.RSADecrypt(encryptedData, prvkey.ExportParameters(true), false);
//Console.WriteLine("Decrypted plaintext: {0}", ByteConverter.GetString(decryptedData)); //加密长内容
String data = @"RSA 是常用的非对称加密算法。最近使用时却出现了“不正确的长度”的异常，研究发现是由于待加密的数据超长所致。
.NET Framework 中提供的 RSA 算法规定：
待加密的字节数不能超过密钥的长度值除以 8 再减去 11（即：RSACryptoServiceProvider.KeySize / 8 - 11），而加密后得到密文的字节数，正好是密钥的长度值除以 8（即：RSACryptoServiceProvider.KeySize / 8）。
所以，如果要加密较长的数据，则可以采用分段加解密的方式，实现方式如下："; string encrypt = EncrypHelp.Encrypt(data, pubcrt);
Console.WriteLine("Encrypted plaintext: {0}", encrypt);
//string decrypt = EncrypHelp.Decrypt(encrypt, prvcrt);
//Console.WriteLine("Decrypted plaintext: {0}", decrypt); //prvkey.Clear();
pubkey.Clear();
Console.Read(); }
}