trovato la risposta qui:
http://msdn.microsoft.com/en-us/library/ms148409.aspx
grande esempio:
using System;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using System.IO;
using System.Text;
// To run this sample use the Certificate Creation Tool (Makecert.exe) to generate a test X.509 certificate and
// place it in the local user store.
// To generate an exchange key and make the key exportable run the following command from a Visual Studio command prompt:
//makecert -r -pe -n "CN=CERT_SIGN_TEST_CERT" -b 01/01/2010 -e 01/01/2012 -sky exchange -ss my
namespace X509CertEncrypt
{
class Program
{
// Path variables for source, encryption, and
// decryption folders. Must end with a backslash.
private static string encrFolder = @"C:\Encrypt\";
private static string decrFolder = @"C:\Decrypt\";
private static string originalFile = "TestData.txt";
private static string encryptedFile = "TestData.enc";
static void Main(string[] args)
{
// Create an input file with test data.
StreamWriter sw = File.CreateText(originalFile);
sw.WriteLine("Test data to be encrypted");
sw.Close();
// Get the certifcate to use to encrypt the key.
X509Certificate2 cert = GetCertificateFromStore("CN=CERT_SIGN_TEST_CERT");
if (cert == null)
{
Console.WriteLine("Certificatge 'CN=CERT_SIGN_TEST_CERT' not found.");
Console.ReadLine();
}
// Encrypt the file using the public key from the certificate.
EncryptFile(originalFile, (RSACryptoServiceProvider)cert.PublicKey.Key);
// Decrypt the file using the private key from the certificate.
DecryptFile(encryptedFile, (RSACryptoServiceProvider)cert.PrivateKey);
//Display the original data and the decrypted data.
Console.WriteLine("Original: {0}", File.ReadAllText(originalFile));
Console.WriteLine("Round Trip: {0}", File.ReadAllText(decrFolder + originalFile));
Console.WriteLine("Press the Enter key to exit.");
Console.ReadLine();
}
private static X509Certificate2 GetCertificateFromStore(string certName)
{
// Get the certificate store for the current user.
X509Store store = new X509Store(StoreLocation.CurrentUser);
try
{
store.Open(OpenFlags.ReadOnly);
// Place all certificates in an X509Certificate2Collection object.
X509Certificate2Collection certCollection = store.Certificates;
// If using a certificate with a trusted root you do not need to FindByTimeValid, instead:
// currentCerts.Find(X509FindType.FindBySubjectDistinguishedName, certName, true);
X509Certificate2Collection currentCerts = certCollection.Find(X509FindType.FindByTimeValid, DateTime.Now, false);
X509Certificate2Collection signingCert = currentCerts.Find(X509FindType.FindBySubjectDistinguishedName, certName, false);
if (signingCert.Count == 0)
return null;
// Return the first certificate in the collection, has the right name and is current.
return signingCert[0];
}
finally
{
store.Close();
}
}
// Encrypt a file using a public key.
private static void EncryptFile(string inFile, RSACryptoServiceProvider rsaPublicKey)
{
using (AesManaged aesManaged = new AesManaged())
{
// Create instance of AesManaged for
// symetric encryption of the data.
aesManaged.KeySize = 256;
aesManaged.BlockSize = 128;
aesManaged.Mode = CipherMode.CBC;
using (ICryptoTransform transform = aesManaged.CreateEncryptor())
{
RSAPKCS1KeyExchangeFormatter keyFormatter = new RSAPKCS1KeyExchangeFormatter(rsaPublicKey);
byte[] keyEncrypted = keyFormatter.CreateKeyExchange(aesManaged.Key, aesManaged.GetType());
// Create byte arrays to contain
// the length values of the key and IV.
byte[] LenK = new byte[4];
byte[] LenIV = new byte[4];
int lKey = keyEncrypted.Length;
LenK = BitConverter.GetBytes(lKey);
int lIV = aesManaged.IV.Length;
LenIV = BitConverter.GetBytes(lIV);
// Write the following to the FileStream
// for the encrypted file (outFs):
// - length of the key
// - length of the IV
// - ecrypted key
// - the IV
// - the encrypted cipher content
int startFileName = inFile.LastIndexOf("\\") + 1;
// Change the file's extension to ".enc"
string outFile = encrFolder + inFile.Substring(startFileName, inFile.LastIndexOf(".") - startFileName) + ".enc";
Directory.CreateDirectory(encrFolder);
using (FileStream outFs = new FileStream(outFile, FileMode.Create))
{
outFs.Write(LenK, 0, 4);
outFs.Write(LenIV, 0, 4);
outFs.Write(keyEncrypted, 0, lKey);
outFs.Write(aesManaged.IV, 0, lIV);
// Now write the cipher text using
// a CryptoStream for encrypting.
using (CryptoStream outStreamEncrypted = new CryptoStream(outFs, transform, CryptoStreamMode.Write))
{
// By encrypting a chunk at
// a time, you can save memory
// and accommodate large files.
int count = 0;
int offset = 0;
// blockSizeBytes can be any arbitrary size.
int blockSizeBytes = aesManaged.BlockSize/8;
byte[] data = new byte[blockSizeBytes];
int bytesRead = 0;
using (FileStream inFs = new FileStream(inFile, FileMode.Open))
{
do
{
count = inFs.Read(data, 0, blockSizeBytes);
offset += count;
outStreamEncrypted.Write(data, 0, count);
bytesRead += blockSizeBytes;
}
while (count > 0);
inFs.Close();
}
outStreamEncrypted.FlushFinalBlock();
outStreamEncrypted.Close();
}
outFs.Close();
}
}
}
}
// Decrypt a file using a private key.
private static void DecryptFile(string inFile, RSACryptoServiceProvider rsaPrivateKey)
{
// Create instance of AesManaged for
// symetric decryption of the data.
using (AesManaged 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[4];
byte[] LenIV = new byte[4];
// Consruct the file name for the decrypted file.
string outFile = decrFolder + inFile.Substring(0, inFile.LastIndexOf(".")) + ".txt";
// Use FileStream objects to read the encrypted
// file (inFs) and save the decrypted file (outFs).
using (FileStream inFs = new FileStream(encrFolder + inFile, FileMode.Open))
{
inFs.Seek(0, SeekOrigin.Begin);
inFs.Seek(0, SeekOrigin.Begin);
inFs.Read(LenK, 0, 3);
inFs.Seek(4, SeekOrigin.Begin);
inFs.Read(LenIV, 0, 3);
// 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)inFs.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 key and IV
// starting from index 8
// after the length values.
inFs.Seek(8, SeekOrigin.Begin);
inFs.Read(KeyEncrypted, 0, lenK);
inFs.Seek(8 + lenK, SeekOrigin.Begin);
inFs.Read(IV, 0, lenIV);
Directory.CreateDirectory(decrFolder);
// Use RSACryptoServiceProvider
// to decrypt the AesManaged key.
byte[] KeyDecrypted = rsaPrivateKey.Decrypt(KeyEncrypted, false);
// Decrypt the key.
using (ICryptoTransform transform = aesManaged.CreateDecryptor(KeyDecrypted, IV))
{
// Decrypt the cipher text from
// from the FileSteam of the encrypted
// file (inFs) into the FileStream
// for the decrypted file (outFs).
using (FileStream outFs = new FileStream(outFile, FileMode.Create))
{
int count = 0;
int offset = 0;
int blockSizeBytes = aesManaged.BlockSize/8;
byte[] data = new byte[blockSizeBytes];
// By decrypting a chunk a time,
// you can save memory and
// accommodate large files.
// Start at the beginning
// of the cipher text.
inFs.Seek(startC, SeekOrigin.Begin);
using (CryptoStream outStreamDecrypted = new CryptoStream(outFs, transform, CryptoStreamMode.Write))
{
do
{
count = inFs.Read(data, 0, blockSizeBytes);
offset += count;
outStreamDecrypted.Write(data, 0, count);
}
while (count > 0);
outStreamDecrypted.FlushFinalBlock();
outStreamDecrypted.Close();
}
outFs.Close();
}
inFs.Close();
}
}
}
}
}
}
Sembra che l'istanza RSA 'privateKey' non abbia una chiave privata valida. Non so perché. – CodesInChaos
RSA è * molto * lento rispetto ai cifrari simmetrici. Pertanto, si consiglia di crittografare solo una chiave simmetrica generata in modo casuale con RSA e crittografare il messaggio stesso con quella chiave simmetrica. – CodesInChaos
Ciao, c'è una password per il pfx? – Digvijay