大家都知道，屏幕保護密碼最多為16個字符。微軟內置了16字節的密鑰：48EE761D6769A11B7A8C47F85495975F。Windows便用上述密鑰加密你輸入的密碼。其加密過程為：首先將你輸入的密碼字符逐位轉換為其16進制的ASCⅡ碼值（小寫字母先轉為大寫字母），再依次與對應密鑰逐位進行異或運算，把所得16進制值的每一位當作字符，轉換為其16進制ASCII碼，並在其尾加上00作為結束標志，存入注冊表HKEY_CURRENT_USERControlPaneldesktop下的二進制鍵ScreenSave_Data中。
懂得其加密原理後，便不難編程破解我的屏幕保護密碼（即上網密碼）了。本人用VB6.0編制了一讀取注冊表中ScrrenSave_Data值的函數GetBinaryValue(EntryAsString),讀出其值為31434133334335353334323100,去掉其結束標志00，把余下字節轉換為對應的ASCII字符，並把每兩個字符組成一16進制數：1CA33C553421，顯然，密碼為6位，將其與前6字節密鑰逐一異或後便得出密碼的ASCII碼（16進制值）：544D4A485348,對應的密碼明文為TMJHSH，破解成功！用它拔號一試，呵，立刻傳來Modem歡快的叫聲。
附VB源程序：(程序中使用了窗體Form1，文本框Text1，命令按鈕Command1)
1、窗體代碼：
OptionExplicit
DimCryptographAsString
DimiAsInteger
DimjAsInteger
DimkAsInteger
DimCryptographStr(32)AsInteger
DimPWstrAsString
DimPassWordAsString
PrivateSubCommand1_Click()
PWstr=“"
PassWord=“"
Text1.Text=“"
Cryptograph=GetBinaryValue(“ScreenSave_Data")
k=Len(Cryptograph)
Forj=1Tok－1
Fori=32To126
IfMid(Cryptograph,j,1)=Chr(i)Then
CryptographStr(j)=i
EndIf
Nexti
Nextj
i=(k－1)/2'密碼位數為(h－1)/2,根據位數選擇解密過程。
SelectCasei
Case16
GoTo16
Case15
GoTo15
Case14
GoTo14
Case13
GoTo13
Case12
GoTo12
Case11
GoTo11
Case10
GoTo10
Case9
GoTo9
Case8
GoTo8
Case7
GoTo7
Case6
GoTo6
Case5
GoTo5
Case4
GoTo4
Case3
GoTo3
Case2
GoTo2
Case1
GoTo1
CaseElse
End
EndSelect
16:PWstr=PWstr＆Chr((“＆H"＆Chr(CryptographStr(31))＆Chr(CryptographStr(32)))Xor＆H5F)
15:PWstr=PWstr＆Chr((“＆H"＆Chr(CryptographStr(29))＆Chr(CryptographStr(30)))Xor＆H97)
14:PWstr=PWstr＆Chr((“＆H"＆Chr(CryptographStr(27))＆Chr(CryptographStr(28)))Xor＆H95)
13:PWstr=PWstr＆Chr((“＆H"＆Chr(CryptographStr(25))＆Chr(CryptographStr(26)))Xor＆H54)
12:PWstr=PWstr＆Chr((“＆H"＆Chr(CryptographStr(23))＆Chr(CryptographStr(24)))Xor＆HF8)
11:PWstr=PWstr＆Chr((“＆H"＆Chr(CryptographStr(21))＆Chr(CryptographStr(22)))Xor＆H47)
10:PWstr=PWstr＆Chr((“＆H"＆Chr(CryptographStr(19))＆Chr(CryptographStr(20)))Xor＆H8C)
9:PWstr=PWstr＆Chr((“＆H"＆Chr(CryptographStr(17))＆Chr(CryptographStr(18)))Xor＆H7A)
8:PWstr=PWstr＆Chr((“＆H"＆Chr(CryptographStr(15))＆Chr(CryptographStr(16)))Xor＆H1B)
7:PWstr=PWstr＆Chr((“＆H"＆Chr(CryptographStr(13))＆Chr(CryptographStr(14)))Xor＆HA1)
6:PWstr=PWstr＆Chr((“＆H"＆Chr(CryptographStr(11))＆Chr(CryptographStr(12)))Xor＆H69)
5:PWstr=PWstr＆Chr((“＆H"＆Chr(CryptographStr(9))＆Chr(CryptographStr(10)))Xor＆H67)
4:PWstr=PWstr＆Chr((“＆H"＆Chr(CryptographStr(7))＆Chr(CryptographStr(8)))Xor＆H1D)
3:PWstr=PWstr＆Chr((“＆H"＆Chr(CryptographStr(5))＆Chr(CryptographStr(6)))Xor＆H76)
2:PWstr=PWstr＆Chr((“＆H"＆Chr(CryptographStr(3))＆Chr(CryptographStr(4)))Xor＆HEE)
1:PWstr=PWstr＆Chr((“＆H"＆Chr(CryptographStr(1))＆Chr(CryptographStr(2)))Xor＆H48)
Fori=iTo1Step－1'所得PWstr的值為密碼的倒序列，將其倒置便得出密碼。
PassWord=PassWord＆Mid(PWstr,i,1)
Nexti
Text1.Text=PassWord'在文本框內顯示密碼。
EndSub
2、模塊代碼：
OptionExplicit
ConstERROR_SUCCESS=0＆
ConstERROR_BADDB=1009＆
ConstERROR_BADKEY=1010＆
ConstREG_EXPAND_SZ=2＆
ConstREG_BINARY=3＆
ConstKEY_QUERY_VALUE=＆H1＆
ConstKEY_ENUMERATE_SUB_KEYS=＆H8＆
ConstKEY_NOTIFY=＆H10＆
ConstREAD_CONTROL=＆H20000
ConstSTANDARD_RIGHTS_READ=READ_CONTROL
ConstKEY_READ=STANDARD_RIGHTS_READOrKEY_QUERY_VALUEOrKEY_ENUMERATE_SUB_KEYSOrKEY_NOTIFY
ConstHKEY_CURRENT_USER=＆H80000001
DimhKeyAsLong,MainKeyHandleAsLong
DimrtnAsLong,lBufferAsLong,sBufferAsString,SubKeyAsString
DimlBufferSizeAsLong
DeclareFunctionRegOpenKeyExLib“advapi32.dll"Alias“RegOpenKeyExA"(ByValhKeyAsLong,ByVallpSubKeyAsString,ByValulOptionsAsLong,ByValsamDesiredAsLong,phkResultAsLong)AsLong
DeclareFunctionRegCloseKeyLib“advapi32.dll"(ByValhKeyAsLong)AsLong
DeclareFunctionRegQueryValueExLib“advapi32.dll"Alias“RegQueryValueExA"(ByValhKeyAsLong,ByVallpValueNameAsString,ByVallpReservedAsLong,lpTypeAsLong,ByVallpDataAsString,lpcbDataAsLong)AsLong
FunctionGetBinaryValue(EntryAsString)
MainKeyHandle=HKEY_CURRENT_USER
SubKey=“ControlPaneldesktop"
rtn=RegOpenKeyEx(MainKeyHandle,SubKey,0,KEY_READ,hKey)
Ifrtn=ERROR_SUCCESSThen'如果HKEY_CURRENT_USERControlPaneldesktop鍵被成功打開
lBufferSize=1
rtn=RegQueryValueEx(hKey,Entry,0,REG_BINARY,0,lBufferSize)'讀取ScreenSave_Data的值
sBuffer=Space(lBufferSize)
rtn=RegQueryValueEx(hKey,Entry,0,REG_BINARY,sBuffer,lBufferSize)
Ifrtn=ERROR_SUCCESSThen'如果讀取ScreenSave_Data的值成功
rtn=RegCloseKey(hKey)
GetBinaryValue=sBuffer'函數返回ScreenSave_Data的值
Else'如果讀取ScreenSave_Data的值不成功
CallErrorMsg
End
EndIf
Else'如果HKEY_CURRENT_USERControlPaneldesktop鍵不能打開
CallErrorMsg'調用ErrorMsg()過程
End
EndIf
EndFunction
PrivateSubErrorMsg()'顯示錯誤信息過程
SelectCasertn
CaseERROR_BADDB
MsgBox(“您的計算機注冊表有錯誤!")
CaseERROR_BADKEY,REG_EXPAND_SZ
MsgBox(“您的計算機未設屏保密碼！")
CaseElse
MsgBox(“破解過程中遇到未知錯誤，錯誤號："＆Str＄(rtn))
EndSelect
EndSub->
