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MD5不可逆加密算法的ASP实现实例

2008-02-23 05:25:59来源：互联网阅读 ()

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Private Const BITS_TO_A_BYTE = 8
Private Const BYTES_TO_A_WORD = 4
Private Const BITS_TO_A_WORD = 32

Private m_lOnBits(30)
Private m_l2Power(30)

Private Function LShift(lValue, iShiftBits)
If iShiftBits = 0 Then
LShift = lValue
Exit Function
ElseIf iShiftBits = 31 Then
If lValue And 1 Then
LShift = &H80000000
Else
LShift = 0
End If
Exit Function
ElseIf iShiftBits < 0 Or iShiftBits > 31 Then
Err.Raise 6
End If

If (lValue And m_l2Power(31 - iShiftBits)) Then
LShift = ((lValue And m_lOnBits(31 - (iShiftBits 1))) * m_l2Power(iShiftBits)) Or &H80000000
Else
LShift = ((lValue And m_lOnBits(31 - iShiftBits)) * m_l2Power(iShiftBits))
End If
End Function

Private Function RShift(lValue, iShiftBits)
If iShiftBits = 0 Then
RShift = lValue
Exit Function
ElseIf iShiftBits = 31 Then
If lValue And &H80000000 Then
RShift = 1
Else
RShift = 0
End If
Exit Function
ElseIf iShiftBits < 0 Or iShiftBits > 31 Then
Err.Raise 6
End If

RShift = (lValue And &H7FFFFFFE) \ m_l2Power(iShiftBits)

If (lValue And &H80000000) Then
RShift = (RShift Or (&H40000000 \ m_l2Power(iShiftBits - 1)))
End If
End Function

Private Function RotateLeft(lValue, iShiftBits)
RotateLeft = LShift(lValue, iShiftBits) Or RShift(lValue, (32 - iShiftBits))
End Function

Private Function AddUnsigned(lX, lY)
Dim lX4
Dim lY4
Dim lX8
Dim lY8
Dim lResult

lX8 = lX And &H80000000
lY8 = lY And &H80000000
lX4 = lX And &H40000000
lY4 = lY And &H40000000

lResult = (lX And &H3FFFFFFF) (lY And &H3FFFFFFF)

If lX4 And lY4 Then
lResult = lResult Xor &H80000000 Xor lX8 Xor lY8
ElseIf lX4 Or lY4 Then
If lResult And &H40000000 Then
lResult = lResult Xor &HC0000000 Xor lX8 Xor lY8
Else
lResult = lResult Xor &H40000000 Xor lX8 Xor lY8
End If
Else
lResult = lResult Xor lX8 Xor lY8
End If

AddUnsigned = lResult
End Function

Private Function md5_F(x, y, z)
md5_F = (x And y) Or ((Not x) And z)
End Function

Private Function md5_G(x, y, z)
md5_G = (x And z) Or (y And (Not z))
End Function

Private Function md5_H(x, y, z)
md5_H = (x Xor y Xor z)
End Function

Private Function md5_I(x, y, z)
md5_I = (y Xor (x Or (Not z)))
End Function

Private Sub md5_FF(a, b, c, d, x, s, ac)
a = AddUnsigned(a, AddUnsigned(AddUnsigned(md5_F(b, c, d), x), ac))
a = RotateLeft(a, s)
a = AddUnsigned(a, b)
End Sub

Private Sub md5_GG(a, b, c, d, x, s, ac)
a = AddUnsigned(a, AddUnsigned(AddUnsigned(md5_G(b, c, d), x), ac))
a = RotateLeft(a, s)
a = AddUnsigned(a, b)
End Sub

Private Sub md5_HH(a, b, c, d, x, s, ac)
a = AddUnsigned(a, AddUnsigned(AddUnsigned(md5_H(b, c, d), x), ac))
a = RotateLeft(a, s)
a = AddUnsigned(a, b)
End Sub

Private Sub md5_II(a, b, c, d, x, s, ac)
a = AddUnsigned(a, AddUnsigned(AddUnsigned(md5_I(b, c, d), x), ac))
a = RotateLeft(a, s)
a = AddUnsigned(a, b)
End Sub

Private Function ConvertToWordArray(sMessage)
Dim lMessageLength
Dim lNumberOfWords
Dim lWordArray()
Dim lBytePosition
Dim lByteCount
Dim lWordCount

Const MODULUS_BITS = 512
Const CONGRUENT_BITS = 448

lMessageLength = Len(sMessage)

lNumberOfWords = (((lMessageLength ((MODULUS_BITS - CONGRUENT_BITS) \ BITS_TO_A_BYTE)) \ (MODULUS_BITS \ BITS_TO_A_BYTE)) 1) * (MODULUS_BITS \ BITS_TO_A_WORD)
ReDim lWordArray(lNumberOfWords - 1)

lBytePosition = 0
lByteCount = 0
Do Until lByteCount >= lMessageLength
lWordCount = lByteCount \ BYTES_TO_A_WORD
lBytePosition = (lByteCount Mod BYTES_TO_A_WORD) * BITS_TO_A_BYTE
lWordArray(lWordCount) = lWordArray(lWordCount) Or LShift(Asc(Mid(sMessage, lByteCount 1, 1)), lBytePosition)
lByteCount = lByteCount 1
Loop

lWordCount = lByteCount \ BYTES_TO_A_WORD
lBytePosition = (lByteCount Mod BYTES_TO_A_WORD) * BITS_TO_A_BYTE

lWordArray(lWordCount) = lWordArray(lWordCount) Or LShift(&H80, lBytePosition)

lWordArray(lNumberOfWords - 2) = LShift(lMessageLength, 3)
lWordArray(lNumberOfWords - 1) = RShift(lMessageLength, 29)

ConvertToWordArray = lWordArray

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