VB中实现MD5加密

Private Const S11 = 7
Private Const S12 = 12
Private Const S13 = 17
Private Const S14 = 22
Private Const S21 = 5
Private Const S22 = 9
Private Const S23 = 14
Private Const S24 = 20
Private Const S31 = 4
Private Const S32 = 11
Private Const S33 = 16
Private Const S34 = 23
Private Const S41 = 6
Private Const S42 = 10
Private Const S43 = 15
Private Const S44 = 21

'=
'= Class Variables
'=
Private State(4) As Long
Private ByteCounter As Long
Private ByteBuffer(63) As Byte

'=
'= Class Properties
'=
Property Get RegisterA() As String
    RegisterA = State(1)
End Property

Property Get RegisterB() As String
    RegisterB = State(2)
End Property

Property Get RegisterC() As String
    RegisterC = State(3)
End Property

Property Get RegisterD() As String
    RegisterD = State(4)
End Property

'=
'= Class Functions
'=

'
' Function to quickly digest a file into a hex string
'
Public Function DigestFileToHexStr(FileName As String) As String
    Open FileName For Binary Access Read As #1
    MD5Init
    Do While Not EOF(1)
        Get #1, , ByteBuffer
        If Loc(1) < LOF(1) Then
            ByteCounter = ByteCounter + 64
            MD5Transform ByteBuffer
        End If
    Loop
    ByteCounter = ByteCounter + (LOF(1) Mod 64)
    Close #1
    MD5Final
    DigestFileToHexStr = GetValues
End Function

'
' Function to digest a text string and output the result as a string
' of hexadecimal characters.
'
Public Function DigestStrToHexStr(SourceString As String) As String
    MD5Init
    MD5Update Len(SourceString), StringToArray(SourceString)
    MD5Final
    DigestStrToHexStr = GetValues
End Function

'
' A utility function which converts a string into an array of
' bytes.
'
Private Function StringToArray(InString As String) As Byte()
    Dim I As Integer
    Dim bytBuffer() As Byte
    ReDim bytBuffer(Len(InString))
    For I = 0 To Len(InString) - 1
        bytBuffer(I) = Asc(Mid(InString, I + 1, 1))
    Next I
    StringToArray = bytBuffer
End Function

'
' Concatenate the four state vaules into one string
'
Public Function GetValues() As String
    GetValues = LongToString(State(1)) & LongToString(State(2)) & LongToString(State(3)) & LongToString(State(4))
End Function

'
' Convert a Long to a Hex string
'
Private Function LongToString(Num As Long) As String
        Dim a As Byte
        Dim b As Byte
        Dim c As Byte
        Dim d As Byte
       
        a = Num And &HFF&
        If a < 16 Then
            LongToString = "0" & Hex(a)
        Else
            LongToString = Hex(a)
        End If
              
        b = (Num And &HFF00&) \ 256
        If b < 16 Then
            LongToString = LongToString & "0" & Hex(b)
        Else
            LongToString = LongToString & Hex(b)
        End If
       
        c = (Num And &HFF0000) \ 65536
        If c < 16 Then
            LongToString = LongToString & "0" & Hex(c)
        Else
            LongToString = LongToString & Hex(c)
        End If
      
        If Num < 0 Then
            d = ((Num And &H7F000000) \ 16777216) Or &H80&
        Else
            d = (Num And &HFF000000) \ 16777216
        End If
       
        If d < 16 Then
            LongToString = LongToString & "0" & Hex(d)
        Else
            LongToString = LongToString & Hex(d)
        End If
   
End Function