Wie sicher ist eine Word Dokumenten Verschlüsselung mit Passwort?

5 min Suche. Speziell VBA Passwörter, man muss nur mit einem Hex-Editor 2 Bytes ändern und das Passwort ist weg. Sicherer ist eine AES Verschlüsselung.

Einfaches VB Beispiel:

    Public Function Encrypt(ByVal plainText As String, ByVal passPhrase As String, ByVal saltValue As String, ByVal hashAlgorithm As String, ByVal passwordIterations As Integer, ByVal initVector As String, ByVal keySize As Integer) As String

        Dim initVectorBytes As Byte()
        initVectorBytes = Encoding.ASCII.GetBytes(initVector)

        Dim saltValueBytes As Byte()
        saltValueBytes = Encoding.ASCII.GetBytes(saltValue)

        Dim plainTextBytes As Byte()
        plainTextBytes = Encoding.UTF8.GetBytes(plainText)

        Dim password As Rfc2898DeriveBytes = New Rfc2898DeriveBytes(passPhrase, saltValueBytes, passwordIterations)
        Dim keyBytes As Byte()
        keyBytes = password.GetBytes(CInt(keySize / 8))

        Dim symmetricKey As RijndaelManaged
        symmetricKey = New RijndaelManaged()
        symmetricKey.Mode = CipherMode.CBC

        Dim encryptor As ICryptoTransform
        encryptor = symmetricKey.CreateEncryptor(keyBytes, initVectorBytes)

        Dim memoryStream As MemoryStream
        memoryStream = New MemoryStream()

        Dim cryptoStream As CryptoStream
        cryptoStream = New CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write)
        cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length)
        cryptoStream.FlushFinalBlock()

        Dim cipherTextBytes As Byte()
        cipherTextBytes = memoryStream.ToArray()
        memoryStream.Close()
        cryptoStream.Close()

        Dim cipherText As String
        cipherText = Convert.ToBase64String(cipherTextBytes)
        Encrypt = cipherText

    End Function

    Public Function Decrypt(ByVal cipherText As String, ByVal passPhrase As String, ByVal saltValue As String, ByVal hashAlgorithm As String, ByVal passwordIterations As Integer, ByVal initVector As String, ByVal keySize As Integer) As String

        On Error Resume Next

        Dim initVectorBytes As Byte()
        initVectorBytes = Encoding.ASCII.GetBytes(initVector)

        Dim saltValueBytes As Byte()
        saltValueBytes = Encoding.ASCII.GetBytes(saltValue)

        Dim cipherTextBytes As Byte()
        cipherTextBytes = Convert.FromBase64String(cipherText)

        Dim password As Rfc2898DeriveBytes = New Rfc2898DeriveBytes(passPhrase, saltValueBytes, passwordIterations)
        Dim keyBytes As Byte()
        keyBytes = password.GetBytes(CInt(keySize / 8))

        Dim symmetricKey As RijndaelManaged
        symmetricKey = New RijndaelManaged()
        symmetricKey.Mode = CipherMode.CBC

        Dim decryptor As ICryptoTransform
        decryptor = symmetricKey.CreateDecryptor(keyBytes, initVectorBytes)

        Dim memoryStream As MemoryStream
        memoryStream = New MemoryStream(cipherTextBytes)

        Dim cryptoStream As CryptoStream
        cryptoStream = New CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read)

        Dim plainTextBytes As Byte()
        ReDim plainTextBytes(cipherTextBytes.Length)

        Dim decryptedByteCount As Integer
        decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length)

        memoryStream.Close()
        cryptoStream.Close()

        Dim plainText As String
        plainText = Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount)

        Decrypt = plainText
    End Function

Bei aktuellen Versionen so sicher wie das Passwort, dass du verwendest - zu "sicheren Passwörtern" und dem "Knacken" von Passwörtern habe ich hier einiges erklärt: https://www.gutefrage.net/frage/welche-passwoerterwuerdet-ihr-nie-nutzen#answer-490617093

Word benutzt seit Office 2007 zur Dokumenten-Verschlüsselung den AES-Algorithmus, der als sehr sicher gilt. Natürlich sollte man das Passwort so wählen, dass es nicht leicht zu erraten ist.

Ältere Versionen als Office 2007 benutzen hingegen andere, leicht zu knackende Verfahren.