public void EncryptFile(string fileToEncodePath, string fileResultPath, string recieverPublicKeyFilePath)
{
var recieverPublicKey = ReadRsaKey(recieverPublicKeyFilePath);
// генерим ключ для DES
var desKeyBytes = new byte[9];
_rand.GetBytes(desKeyBytes);
desKeyBytes[desKeyBytes.Length - 1] = 0; // всегда неотрицательное
var desKey = new BigInteger(desKeyBytes);
// шифруем файл
var bytesToEncrypt = File.ReadAllBytes(fileToEncodePath);
var encryptedData = DesFileEncoder.EncryptBytes(bytesToEncrypt, desKey.ToByteArray());
// шифруем ключ DES
var desKeyEncoded = BigInteger.ModPow(desKey, recieverPublicKey.Item1, recieverPublicKey.Item2);
// пишем в файл
using (var fs = new FileStream(fileResultPath, FileMode.Create))
using (var bw = new BinaryWriter(fs))
{
var desKeyEncodedBytes = desKeyEncoded.ToByteArray();
bw.Write(desKeyEncodedBytes.Length);
bw.Write(desKeyEncodedBytes);
bw.Write(encryptedData.Length);
bw.Write(encryptedData);
}
}
public void DecryptFile(string fileToDecrypt, string fileResultPath, string privateKeyOfReceiver)
{
var recieverPrivateKey = ReadRsaKey(privateKeyOfReceiver);
byte[] desKeyBytes, encryptedDataBytes;
using (var fs = new FileStream(fileToDecrypt, FileMode.Open))
using (var bw = new BinaryReader(fs))
{
var desKeyLength = bw.ReadInt32();
desKeyBytes = bw.ReadBytes(desKeyLength);
var encLength = bw.ReadInt32();
encryptedDataBytes = bw.ReadBytes(encLength);
}
// получили зашифрованный ключ DES
var desKeyBytesForBigInt = new byte[desKeyBytes.Length + 1];
desKeyBytes.CopyTo(desKeyBytesForBigInt, 0);
var desKeyEncrypted = new BigInteger(desKeyBytesForBigInt);
var desKeyDecrypted = BigInteger.ModPow(desKeyEncrypted, recieverPrivateKey.Item1, recieverPrivateKey.Item2).ToByteArray();
var decryptedData = DesFileEncoder.DecryptBytes(encryptedDataBytes, desKeyDecrypted);
File.WriteAllBytes(fileResultPath, decryptedData);
}
