(Delphi) Determine if a Zip is Encrypted or Password-Protected

Determins whether or not a zip archive is AES encrypted or password-protected.

Download Chilkat 32-bit Zip ActiveX (.msi) (includes objects for .zip, .gz, .bz2, and .Z)

Download All 32-bit Chilkat ActiveX Components (.zip)

Download All 64-bit Chilkat ActiveX Components (.zip)

uses
    Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
    Dialogs, StdCtrls,
    ChilkatZip2Lib_TLB,
    OleCtrls;

...

procedure TForm1.Button1Click(Sender: TObject);
var
zip: TChilkatZip2;
success: Integer;
bPwdProt: Integer;
encValue: Integer;

begin
zip := TChilkatZip2.Create(Self);

//  Any string unlocks the component for the 1st 30-days.
success := zip.UnlockComponent('Anything for 30-day trial');
if (success <> 1) then
  begin
    Memo1.Lines.Add(zip.LastErrorText);
    Exit;
  end;

//  An encrypted or password-protected zip can be opened
//  without specifying the password.  However, the contents
//  of the files cannot be unzipped without providing the correct
//  password.

success := zip.OpenZip('something.zip');
if (success <> 1) then
  begin
    Memo1.Lines.Add(zip.LastErrorText);
    Exit;
  end;

//  If the zip is password-protected, meaning that it uses
//  the old (insecure) Zip 2.0 encryption, then the
//  PasswordProtect property will be 1
bPwdProt := zip.PasswordProtect;
if (bPwdProt) then
  begin
    Memo1.Lines.Add('This zip is password-protected.');
  end;

//  If the zip is AES encrypted (WinZip compatible) then
//  the Encryption property will be equal to 4.
encValue := zip.Encryption;
if (encValue = 4) then
  begin
    Memo1.Lines.Add('This zip is AES encrypted.');
  end;

//  If the Encryption property = 0, then the zip is NOT
//  strong encrypted, and is either password-protected or
//  entirely unencrypted, depending on the value of the
//  PasswordProtect property.

//  If the Encryption property = 1, 2, or 3, then the zip was
//  encrypted using AES, Blowfish, or Twofish using a
//  Chilkat-specific encryption format that was implemented
//  prior to the publication of the Zip AES standard.

zip.CloseZip();
end;