mmd5.bas

算法解密

    G = (x And z) Or (y And (Not z))
End Function

'*******************************************************************************
' H (FUNCTION)
'
' DESCRIPTION:
' MD5's H function
'*******************************************************************************
Private Function H(ByVal x As Long, _
                   ByVal y As Long, _
                   ByVal z As Long) As Long
    H = (x Xor y Xor z)
End Function

'*******************************************************************************
' I (FUNCTION)
'
' DESCRIPTION:
' MD5's I function
'*******************************************************************************
Private Function I(ByVal x As Long, _
                   ByVal y As Long, _
                   ByVal z As Long) As Long
    I = (y Xor (x Or (Not z)))
End Function

'*******************************************************************************
' FF (SUB)
'
' DESCRIPTION:
' MD5's FF procedure
'*******************************************************************************
Private Sub FF(a As Long, _
               ByVal b As Long, _
               ByVal c As Long, _
               ByVal d As Long, _
               ByVal x As Long, _
               ByVal s As Long, _
               ByVal ac As Long)
    a = AddUnsigned(a, AddUnsigned(AddUnsigned(F(b, c, d), x), ac))
    a = RotateLeft(a, s)
    a = AddUnsigned(a, b)
End Sub

'*******************************************************************************
' GG (SUB)
'
' DESCRIPTION:
' MD5's GG procedure
'*******************************************************************************
Private Sub GG(a As Long, _
               ByVal b As Long, _
               ByVal c As Long, _
               ByVal d As Long, _
               ByVal x As Long, _
               ByVal s As Long, _
               ByVal ac As Long)
    a = AddUnsigned(a, AddUnsigned(AddUnsigned(G(b, c, d), x), ac))
    a = RotateLeft(a, s)
    a = AddUnsigned(a, b)
End Sub

'*******************************************************************************
' HH (SUB)
'
' DESCRIPTION:
' MD5's HH procedure
'*******************************************************************************
Private Sub HH(a As Long, _
               ByVal b As Long, _
               ByVal c As Long, _
               ByVal d As Long, _
               ByVal x As Long, _
               ByVal s As Long, _
               ByVal ac As Long)
    a = AddUnsigned(a, AddUnsigned(AddUnsigned(H(b, c, d), x), ac))
    a = RotateLeft(a, s)
    a = AddUnsigned(a, b)
End Sub

'*******************************************************************************
' II (SUB)
'
' DESCRIPTION:
' MD5's II procedure
'*******************************************************************************
Private Sub II(a As Long, _
               ByVal b As Long, _
               ByVal c As Long, _
               ByVal d As Long, _
               ByVal x As Long, _
               ByVal s As Long, _
               ByVal ac As Long)
    a = AddUnsigned(a, AddUnsigned(AddUnsigned(I(b, c, d), x), ac))
    a = RotateLeft(a, s)
    a = AddUnsigned(a, b)
End Sub

'*******************************************************************************
' ConvertToWordArray (FUNCTION)
'
' PARAMETERS:
' (In/Out) - sMessage - String - String message
'
' RETURN VALUE:
' Long() - Converted message as long array
'
' DESCRIPTION:
' Takes the string message and puts it in a long array with padding according to
' the MD5 rules. Note we are using only the first byte of each character with
' the AscB function, this may well mess up in unicode/dbcs situations where you
' are comparing what was generated on two different PCs with different
' character sets.
'*******************************************************************************
Private Function ConvertToWordArray(sMessage As String) As Long()
    Dim lMessageLength  As Long
    Dim lNumberOfWords  As Long
    Dim lWordArray()    As Long
    Dim lBytePosition   As Long
    Dim lByteCount      As Long
    Dim lWordCount      As Long
    Dim lChar           As Long
    
    Const MODULUS_BITS      As Long = 512
    Const CONGRUENT_BITS    As Long = 448
    
    lMessageLength = Len(sMessage)
    
    ' Get padded number of words. Message needs to be congruent to 448 bits,
    ' modulo 512 bits. If it is exactly congruent to 448 bits, modulo 512 bits
    ' it must still have another 512 bits added. 512 bits = 64 bytes
    ' (or 16 * 4 byte words), 448 bits = 56 bytes. This means lMessageSize must
    ' be a multiple of 16 (i.e. 16 * 4 (bytes) * 8 (bits))
    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)
    
    ' Combine each block of 4 bytes (ascii code of character) into one long
    ' value and store in the message. The high-order (most significant) bit of
    ' each byte is listed first. However, the low-order (least significant) byte
    ' is given first in each word.
    lBytePosition = 0
    lByteCount = 0
    Do Until lByteCount >= lMessageLength
        ' Each word is 4 bytes
        lWordCount = lByteCount \ BYTES_TO_A_WORD
                
        ' The bytes are put in the word from the right most edge
        lBytePosition = (lByteCount Mod BYTES_TO_A_WORD) * BITS_TO_A_BYTE
        lChar = AscB(Mid(sMessage, lByteCount + 1, 1))
        lWordArray(lWordCount) = lWordArray(lWordCount) Or LShift(lChar, lBytePosition)
        lByteCount = lByteCount + 1
    Loop

    ' Terminate according to MD5 rules with a 1 bit, zeros and the length in
    ' bits stored in the last two words
    lWordCount = lByteCount \ BYTES_TO_A_WORD
    lBytePosition = (lByteCount Mod BYTES_TO_A_WORD) * BITS_TO_A_BYTE

    ' Add a terminating 1 bit, all the rest of the bits to the end of the
    ' word array will default to zero
    lWordArray(lWordCount) = lWordArray(lWordCount) Or LShift(&H80, lBytePosition)

    ' We put the length of the message in bits into the last two words, to get
    ' the length in bits we need to multiply by 8 (or left shift 3). This left
    ' shifted value is put in the first word. Any bits shifted off the left edge
    ' need to be put in the second word, we can work out which bits by shifting
    ' right the length by 29 bits.
    lWordArray(lNumberOfWords - 2) = LShift(lMessageLength, 3)
    lWordArray(lNumberOfWords - 1) = RShift(lMessageLength, 29)
    
    ConvertToWordArray = lWordArray
End Function

'*******************************************************************************
' WordToHex (FUNCTION)
'
' PARAMETERS:
' (In) - lValue - Long - Long value to convert
'
' RETURN VALUE:
' String - Hex value to return
'
' DESCRIPTION:
' Takes a long integer and due to the bytes reverse order it extracts the
' individual bytes and converts them to hex appending them for an overall hex
' value
'*******************************************************************************
Private Function WordToHex(ByVal lValue As Long) As String
    Dim lByte As Long
    Dim lCount As Long
    
    For lCount = 0 To 3
        lByte = RShift(lValue, lCount * BITS_TO_A_BYTE) And _
            m_lOnBits(BITS_TO_A_BYTE - 1)
        WordToHex = WordToHex & Right("0" & Hex(lByte), 2)
    Next
End Function

'*******************************************************************************
' MD5 (FUNCTION)
'
' PARAMETERS:
' (In/Out) - sMessage - String - String to be digested
'
' RETURN VALUE:
' String - The MD5 digest
'
' DESCRIPTION:
' This function takes a string message and generates an MD5 digest for it.
' sMessage can be up to the VB string length limit of 2^31 (approx. 2 billion)
' characters.
'
' NOTE: Due to the way in which the string is processed the routine assumes a
' single byte character set. VB passes unicode (2-byte) character strings, the
' ConvertToWordArray function uses on the first byte for each character. This
' has been done this way for ease of use, to make the routine truely portable
' you could accept a byte array instead, it would then be up to the calling
' routine to make sure that the byte array is generated from their string in
' a manner consistent with the string type.
'*******************************************************************************
Public Function MD5(sMessage As String) As String
    Dim x() As Long
    Dim k   As Long
    Dim AA  As Long
    Dim BB  As Long
    Dim CC  As Long
    Dim DD  As Long
    Dim a   As Long
    Dim b   As Long
    Dim c   As Long
    Dim d   As Long
    
    Const S11 As Long = 7
    Const S12 As Long = 12
    Const S13 As Long = 17
    Const S14 As Long = 22
    Const S21 As Long = 5
    Const S22 As Long = 9
    Const S23 As Long = 14
    Const S24 As Long = 20
    Const S31 As Long = 4
    Const S32 As Long = 11
    Const S33 As Long = 16
    Const S34 As Long = 23
    Const S41 As Long = 6
    Const S42 As Long = 10
    Const S43 As Long = 15
    Const S44 As Long = 21

    ' Steps 1 and 2.  Append padding bits and length and convert to words
    x = ConvertToWordArray(sMessage)
    
    ' Step 3.  Initialise
    a = &H67452301
    b = &HEFCDAB89
    c = &H98BADCFE
    d = &H10325476

    ' Step 4.  Process the message in 16-word blocks
    For k = 0 To UBound(x) Step 16
        AA = a
        BB = b
        CC = c
        DD = d
    
        ' The hex number on the end of each of the following procedure calls is
        ' an element from the 64 element table constructed with
        ' T(i) = Int(4294967296 * Abs(Sin(i))) where i is 1 to 64.
        '
        ' However, for speed we don't want to calculate the value every time.
        FF a, b, c, d, x(k + 0), S11, &HD76AA478
        FF d, a, b, c, x(k + 1), S12, &HE8C7B756
        FF c, d, a, b, x(k + 2), S13, &H242070DB
        FF b, c, d, a, x(k + 3), S14, &HC1BDCEEE
        FF a, b, c, d, x(k + 4), S11, &HF57C0FAF
        FF d, a, b, c, x(k + 5), S12, &H4787C62A
        FF c, d, a, b, x(k + 6), S13, &HA8304613
        FF b, c, d, a, x(k + 7), S14, &HFD469501
        FF a, b, c, d, x(k + 8), S11, &H698098D8
        FF d, a, b, c, x(k + 9), S12, &H8B44F7AF
        FF c, d, a, b, x(k + 10), S13, &HFFFF5BB1
        FF b, c, d, a, x(k + 11), S14, &H895CD7BE
        FF a, b, c, d, x(k + 12), S11, &H6B901122
        FF d, a, b, c, x(k + 13), S12, &HFD987193
        FF c, d, a, b, x(k + 14), S13, &HA679438E
        FF b, c, d, a, x(k + 15), S14, &H49B40821
    
        GG a, b, c, d, x(k + 1), S21, &HF61E2562
        GG d, a, b, c, x(k + 6), S22, &HC040B340
        GG c, d, a, b, x(k + 11), S23, &H265E5A51
        GG b, c, d, a, x(k + 0), S24, &HE9B6C7AA
        GG a, b, c, d, x(k + 5), S21, &HD62F105D
        GG d, a, b, c, x(k + 10), S22, &H2441453
        GG c, d, a, b, x(k + 15), S23, &HD8A1E681
        GG b, c, d, a, x(k + 4), S24, &HE7D3FBC8
        GG a, b, c, d, x(k + 9), S21, &H21E1CDE6
        GG d, a, b, c, x(k + 14), S22, &HC33707D6
        GG c, d, a, b, x(k + 3), S23, &HF4D50D87
        GG b, c, d, a, x(k + 8), S24, &H455A14ED
        GG a, b, c, d, x(k + 13), S21, &HA9E3E905
        GG d, a, b, c, x(k + 2), S22, &HFCEFA3F8
        GG c, d, a, b, x(k + 7), S23, &H676F02D9
        GG b, c, d, a, x(k + 12), S24, &H8D2A4C8A
            
        HH a, b, c, d, x(k + 5), S31, &HFFFA3942
        HH d, a, b, c, x(k + 8), S32, &H8771F681
        HH c, d, a, b, x(k + 11), S33, &H6D9D6122
        HH b, c, d, a, x(k + 14), S34, &HFDE5380C
        HH a, b, c, d, x(k + 1), S31, &HA4BEEA44
        HH d, a, b, c, x(k + 4), S32, &H4BDECFA9
        HH c, d, a, b, x(k + 7), S33, &HF6BB4B60
        HH b, c, d, a, x(k + 10), S34, &HBEBFBC70
        HH a, b, c, d, x(k + 13), S31, &H289B7EC6
        HH d, a, b, c, x(k + 0), S32, &HEAA127FA
        HH c, d, a, b, x(k + 3), S33, &HD4EF3085
        HH b, c, d, a, x(k + 6), S34, &H4881D05
        HH a, b, c, d, x(k + 9), S31, &HD9D4D039
        HH d, a, b, c, x(k + 12), S32, &HE6DB99E5
        HH c, d, a, b, x(k + 15), S33, &H1FA27CF8
        HH b, c, d, a, x(k + 2), S34, &HC4AC5665
    
        II a, b, c, d, x(k + 0), S41, &HF4292244
        II d, a, b, c, x(k + 7), S42, &H432AFF97
        II c, d, a, b, x(k + 14), S43, &HAB9423A7
        II b, c, d, a, x(k + 5), S44, &HFC93A039
        II a, b, c, d, x(k + 12), S41, &H655B59C3
        II d, a, b, c, x(k + 3), S42, &H8F0CCC92
        II c, d, a, b, x(k + 10), S43, &HFFEFF47D
        II b, c, d, a, x(k + 1), S44, &H85845DD1
        II a, b, c, d, x(k + 8), S41, &H6FA87E4F
        II d, a, b, c, x(k + 15), S42, &HFE2CE6E0
        II c, d, a, b, x(k + 6), S43, &HA3014314
        II b, c, d, a, x(k + 13), S44, &H4E0811A1
        II a, b, c, d, x(k + 4), S41, &HF7537E82
        II d, a, b, c, x(k + 11), S42, &HBD3AF235
        II c, d, a, b, x(k + 2), S43, &H2AD7D2BB
        II b, c, d, a, x(k + 9), S44, &HEB86D391
    
        a = AddUnsigned(a, AA)
        b = AddUnsigned(b, BB)
        c = AddUnsigned(c, CC)
        d = AddUnsigned(d, DD)
    Next
    
    ' Step 5.  Output the 128 bit digest
            '=LCase(WordToHex(a) & WordToHex(b) & WordToHex(c) & WordToHex(d))
    MD5 = LCase(WordToHex(b) & WordToHex(c))
End Function