public static async Task Decrypt(string filePath, string certName, string password)
{
//Read the file in memory so we can overwrite the source with it's original file.
//We also need it in memory so we can extract the key.
var file = (await File.ReadAllBytesAsync(filePath)).ToList();
var encryptedKey = new Collection <byte>();
//Checking the length so we know how much bytes we need to take from the file.
//Different certificates can create different size of keys.
var encryptLength = Encrypter.EncryptKey(Encoding.UTF8.GetBytes("string"), certName, password).Length;
//Extract the key.
for (var i = 0; i < encryptLength; i++)
{
encryptedKey.Add(file[i]);
}
file.RemoveRange(0, encryptLength);
var decryptedKey = DecryptKey(encryptedKey.ToArray(), certName, password);
using (var managed = new AesManaged())
{
//We're using AES encryption, but this time we do not generate the key but pass our decrypted key.
Aes aesKey = Aes.Create();
aesKey.Key = decryptedKey;
byte[] ivKey = new byte[aesKey.IV.Length];
Array.Copy(aesKey.Key, ivKey, aesKey.IV.Length);
aesKey.IV = ivKey;
var decryptor = aesKey.CreateDecryptor();
//We're using truncate mode, so the file opens up and is empty.
using (var fileStream = new FileStream(filePath, FileMode.Truncate))
using (var decryptStream = new CryptoStream(fileStream, decryptor, CryptoStreamMode.Write))
using (var encryptedFileStream = new MemoryStream(file.ToArray()))
await encryptedFileStream.CopyToAsync(decryptStream);
}
}
static void Main(string[] args)
{
Encrypter.Encrypt(File, CertPath, CertPassword).Wait();
Console.ReadKey();
Decrypter.Decrypt(File, CertPath, CertPassword).Wait();
}