我在尝试实现DES加密和解密时遇到错误（虽然我的代码允许不同的实现）
我已就此进行了大量研究，并在Stack Overflow上找到了几个类似的问题，但是他们提供的答案是确保Key和IV在加密和解密过程中是相同的，I似乎已经实现了这一点，所以似乎问题的根源在于其他地方。
以下是我的代码，＃164
行引发异常namespace xNFCE
{
public class Crypto
{
public enum cryptype
{
DES,
THREEDES,
AES
};
// Variables for the file input, output and the password to encrypt the file
string _input, _output;
byte[] _password;
cryptype _type;
/// <summary>
/// Initializes a new instance of the <see cref="xNFCE.Crypto"/> class.
/// </summary>
/// <param name="input">Input.</param>
/// <param name="output">Output.</param>
/// <param name="password">Password.</param>
public Crypto(string input, string output, string password, cryptype type = cryptype.AES)
{
// Set the properties for the encryption
_input = input;
_output = output;
_password = hash(password);
_type = type;
}
/// <summary>
/// Run the appropriate encryption function
/// </summary>
public void Encrypt()
{
switch (_type)
{
case cryptype.DES:
DESenc();
break;
case cryptype.THREEDES:
// TODO Implement
throw new NotImplementedException();
case cryptype.AES:
// TODO Implement
throw new NotImplementedException();
}
}
/// <summary>
/// Run the appropriate decryption function
/// </summary>
public void Decrypt()
{
switch (_type)
{
case cryptype.DES:
DESdec();
break;
case cryptype.THREEDES:
// TODO Implement
throw new NotImplementedException();
case cryptype.AES:
// TODO Implement
throw new NotImplementedException();
}
}
/// <summary>
/// Hash the password and return it as a byte array
/// </summary>
/// <param name="pwd">Pwd.</param>
byte[] hash(String pwd)
{
// System.Text provides .GetBytes() this converts a string to the series of bytes
// Convert the password string to an array of bytes
byte[] bytes = Encoding.ASCII.GetBytes(pwd);
// Create an instance of Managed SHA256
SHA256Managed hashman = new SHA256Managed();
// Hash the array of bytes
byte[] hash = hashman.ComputeHash(bytes);
return hash;
}
/// <summary>
/// This function is called when the user wants to encrypt a file
/// </summary>
void DESenc()
{
// Create file streams for the input and output of the files
FileStream fileInput = new FileStream(_input, FileMode.Open, FileAccess.Read);
// Append the xNFCE extension to the output
FileStream fileEncrypted = new FileStream(_output + GlobalValues.fextension, FileMode.Create, FileAccess.Write);
// Declare an insrance of the DESCryptoServiceProvider class
// This represents the actual encryption and decryption technology that is used on the files
// Other cryptographic techniques can be used here
// TODO implement other encryption techniques
DESCryptoServiceProvider DES = new DESCryptoServiceProvider();
// Each cryptographic technique takes a different syze key, DES takes a 64Bit key which is 8 Bytes (8 Characters)
// If we do not provide a key and IV here, they are randomly generated, meaning we cannot decrypt the file
// Take the first 8 bytes from the password
DES.Key = _password.Take(8).ToArray();
DES.IV = _password.Take(8).ToArray();
// Cretae an instance of the CryptoStream class by using the cryptographic prover to obtain an encrypting object
// and the existing output filestream as part of the constructor.
ICryptoTransform desencrypt = DES.CreateEncryptor();
CryptoStream cryptostream = new CryptoStream(fileEncrypted, desencrypt, CryptoStreamMode.Write);
// Read in the input file and write to the output file while passing through the crypto stream object using the password provided
byte[] bytearrayinput = new byte[fileInput.Length - 1];
fileInput.Read(bytearrayinput, 0, bytearrayinput.Length);
cryptostream.Write(bytearrayinput, 0, bytearrayinput.Length);
}
/// <summary>
/// This function is called when the user wants to decrypt a file
/// </summary>
void DESdec()
{
// This function has two key differences from the encrypt function
// CreateDecryptor is used instead of CreateEncryptor to create the crypto stream object
// When the decrypted text is written to the destination file, the CryptoStream object is now the source isntead of the destination stream
DESCryptoServiceProvider DES = new DESCryptoServiceProvider();
// Take the first 8 bytes from the password
DES.Key = _password.Take(8).ToArray();
DES.IV = _password.Take(8).ToArray();
// Create the file stream to read the encrypted file back
FileStream fileInput = new FileStream(_input, FileMode.Open, FileAccess.Read);
// Create a DES decryptor
ICryptoTransform desdecrypt = DES.CreateDecryptor();
// Create a crypto stream set to read and do a decryption transform on incoming bytes
CryptoStream cryptostream = new CryptoStream(fileInput, desdecrypt, CryptoStreamMode.Read);
// Print the contents of the decrypted file
FileInfo fi = new FileInfo(_output);
string writename = Path.Combine(fi.DirectoryName, Path.GetFileNameWithoutExtension(_output));
StreamWriter fsDecrypted = new StreamWriter(writename);
fsDecrypted.Write(new StreamReader(cryptostream).ReadToEnd());
fsDecrypted.Flush();
fsDecrypted.Close();
}
}
}
注意：我正在使用Xamarin.Android，但我不相信它是相关的
谢谢！ ：）
答案 0 :(得分：2)
问题是加密文件是空的，因此您随后尝试解密将失败的空字符串。
该文件为空，因为CryptoStream永远不会刷新到磁盘。
这与您没有处置任何内容有关，您需要返回并向实现using () {}的任何内容添加IDisposable子句（对CryptoStream执行此操作将正确冲洗它。）
作为最低：
using (CryptoStream cryptostream = new CryptoStream(fileEncrypted, desencrypt, CryptoStreamMode.Write))
{
// Read in the input file and write to the output file while passing through the crypto stream object using the password provided
byte[] bytearrayinput = new byte[fileInput.Length - 1];
fileInput.Read(bytearrayinput, 0, bytearrayinput.Length);
cryptostream.Write(bytearrayinput, 0, bytearrayinput.Length);
}
会导致程序按预期运行。 （但仍在其他地方泄漏）。
（不要对密钥和iv使用相同的值）