利用未公开的API函数来计算MD5

本实例演示使用ADVAPI32.DLL里面三个未公开的API函数来计算字符串的MD5值。

代码如下：

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Option Explicit

Private Type MD5_CTX
    num(1) As Long
    buf(3) As Long
    inputBuf(63) As Byte
    digest(15) As Byte
End Type


Private Declare Function MD5Init Lib "ADVAPI32.DLL" (ByVal lpCtx As Long) As Long
Private Declare Function MD5Update Lib "ADVAPI32.DLL" (ByVal lpCtx As Long, ByVal lpBuf As Long, ByVal nLen As Long) As Long
Private Declare Function MD5Final Lib "ADVAPI32.DLL" (ByVal lpCtx As Long) As Long


Function MD5String(ByVal strSrc As String) As String

    Dim ctx As MD5_CTX, lpCtx As Long, strTmp As String
    
    lpCtx = VarPtr(ctx)
    
    Call MD5Init(lpCtx)
    
    strTmp = StrConv(strSrc, vbFromUnicode)
    
    Call MD5Update(lpCtx, StrPtr(strTmp), LenB(strTmp))
    
    Call MD5Final(lpCtx)

    strTmp = ""
    
    Dim i As Integer
    
    For i = 0 To 15
    
        strTmp = strTmp & Format$(Hex(ctx.digest(i)), "00")
        
    Next
    
    MD5String = strTmp

End Function


Private Sub Command1_Click()
    MsgBox MD5String("123")
End Sub