(VB.NET) Determine if a Zip is Encrypted or Password-Protected

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

Download: Chilkat .NET Assemblies

Dim zip As New Chilkat.Zip()

Dim success As Boolean

'  Any string unlocks the component for the 1st 30-days.
success = zip.UnlockComponent("Anything for 30-day trial")
If (success <> true) Then
    TextBox1.Text = TextBox1.Text & zip.LastErrorText & vbCrLf
    Exit Sub
End If


'  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 <> true) Then
    TextBox1.Text = TextBox1.Text & zip.LastErrorText & vbCrLf
    Exit Sub
End If


'  If the zip is password-protected, meaning that it uses
'  the old (insecure) Zip 2.0 encryption, then the
'  PasswordProtect property will be True
Dim bPwdProt As Boolean
bPwdProt = zip.PasswordProtect
If (bPwdProt) Then
    TextBox1.Text = TextBox1.Text & "This zip is password-protected." & vbCrLf
End If


'  If the zip is AES encrypted (WinZip compatible) then
'  the Encryption property will be equal to 4.
Dim encValue As Long
encValue = zip.Encryption
If (encValue = 4) Then
    TextBox1.Text = TextBox1.Text & "This zip is AES encrypted." & vbCrLf
End If


'  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()