Question

I’ve used AESManaged Class to encrypt a zip file, but it couldn’t be decompressed by winzip/7zip. I can only decompress it after decrypting in my code.

Below is the code I used to encrypt and decrypt. Anyone can help?

private static void EncryptFile(string input, string output, string pwd)
    {
        using (AesManaged aes = new AesManaged())
        {
            FileStream fsCrypt=null;
            try
            {
                byte[] key = Encoding.UTF8.GetBytes(pwd);

                fsCrypt = new FileStream(output, FileMode.Create);

                    using (CryptoStream cs = new CryptoStream(fsCrypt, aes.CreateEncryptor(key, key), CryptoStreamMode.Write))
                    {
                        using (FileStream fsIn = new FileStream(input, FileMode.Open))
                        {
                            int data;

                            while ((data = fsIn.ReadByte()) != -1)
                            {
                                cs.WriteByte((byte)data);
                            }
                            aes.Clear();
                        }
                    }

            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
                aes.Clear();
            }
            finally
            {
                if(fsCrypt!=null)
                {
                    fsCrypt.Dispose();
                }
            }
        }
    }


    private static void DecryptFile(string input, string output, string pwd)
    {
        using (AesManaged aes = new AesManaged())
        {
            FileStream fsCrypt = null;
            try
            {
                byte[] key = Encoding.UTF8.GetBytes(pwd);

                fsCrypt = new FileStream(input, FileMode.Open);
                {

                    using (FileStream fsOut = new FileStream(output, FileMode.Create))
                    {
                        using (CryptoStream cs = new CryptoStream(fsCrypt, aes.CreateDecryptor(key, key), CryptoStreamMode.Read))
                        {
                            int data;

                            while ((data = cs.ReadByte()) != -1)
                            {
                                fsOut.WriteByte((byte)data);
                            }
                            aes.Clear();
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
                aes.Clear();
            }
            finally
            {
                if (fsCrypt != null)
                {
                    fsCrypt.Dispose();
                }
            }
        }
    }

Answer 1

You are overwriting the internal structure of a zip file with your encryption algorithm.
How could you expect that an external zip manager recognizes your encrypted file as a valid zip file?
If you really want to use a password protected zip file then use a library that can do this for you without destroying the zip file structure.

I recommend this library DotNetZip