为什么此代码会禁用 sheet 保护？

Question

以下代码由 this website 提供，我用它来取消保护我不知道密码的工作表。

Sub DisableSheetProtection()
Dim password As String
On Error Resume Next
For i = 65 To 66: For j = 65 To 66
For k = 65 To 66: For l = 65 To 66
For m = 65 To 66: For n = 65 To 66
For o = 65 To 66: For p = 65 To 66
For q = 65 To 66: For r = 65 To 66
For S = 65 To 66: For t = 32 To 126
ActiveSheet.Unprotect Chr(i) & _
Chr(j) & Chr(k) & Chr(l) & _
Chr(m) & Chr(n) & Chr(o) & _
Chr(p) & Chr(q) & Chr(r) & _
Chr(S) & Chr(t)

Next t: Next S: Next r: Next q
Next p: Next o: Next n: Next m
Next l: Next k: Next j: Next i
MsgBox "Sheet protection disabled."
End Sub

问题是：它是如何或为什么起作用的？Chr(65) 是 A，Chr(66) 是 B，Chr(32) 到 Chr(126) 是整个字母表和特殊字符。

基本上，如果您想尝试所有可能性，您需要这样做：

Sub DisableSheetProtection()
    Dim password As String
    On Error Resume Next
    For i = 32 To 126: For j = 32 To 126
    For k = 32 To 126: For l = 32 To 126
    For m = 32 To 126: For n = 32 To 126
    For o = 32 To 126: For p = 32 To 126
    For q = 32 To 126: For r = 32 To 126
    For S = 32 To 126: For t = 32 To 126
    ActiveSheet.Unprotect Chr(i) & _
    Chr(j) & Chr(k) & Chr(l) & _
    Chr(m) & Chr(n) & Chr(o) & _
    Chr(p) & Chr(q) & Chr(r) & _
    Chr(S) & Chr(t)

    Next t: Next S: Next r: Next q
    Next p: Next o: Next n: Next m
    Next l: Next k: Next j: Next i
    MsgBox "Sheet protection disabled."
    End Sub

但是代码工作正常，因为它用于取消保护，您无法打印出正确的密码。我认为这与 VBA unprotect/protect 方法有关。

Answer 1

Internal XL passwords are about as useful for security as tissue paper. The reason is that the passwords you enter (i.e., with Tools/Protect/Protect Worksheet or /Protect Workbook) are not used directly in protection. Instead they are hashed (mathematically transformed) into a much less secure code. Effectively, any password of any length is transformed into a string of 12 characters, the first 11 of which have one of only two possible values. The remaining character can have up to 95 possible values, leading to only

2^11 * 95 = 194,560 potential passwords.

This may seem like a lot, but it only takes a few seconds for a modern computer >to try them all. As a comparison, a 4-character password containing just the 26 lower case alphabet characters has 456,976 combinations, and a 3-character password consisting of lower case, upper case and the digits 0-9 will have 238,328 combinations.

Again, it doesn't matter what your original password is, one of those 194K strings will unlock your sheet or workbook.

更多阅读this。

为什么此代码会禁用 sheet 保护？

Why does this code disable the sheet protection?

vba

excel

passwords

excel-2007

password-protection