md5加密運算是不可逆的，就是說不能通過那壹串古古怪怪的東西算出它原始的樣子。
以下提供VB可用的16位和32位MD5加密函數代碼：
Private?Const?BITS_TO_A_BYTE?=?8Private?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
End?Function
Private?Function?WordToHex(lValue)
Dim?lByte
Dim?lCount
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
Public?Function?MD5(sMessage,?stype)
m_lOnBits(0)?=?CLng(1)
m_lOnBits(1)?=?CLng(3)
m_lOnBits(2)?=?CLng(7)
m_lOnBits(3)?=?CLng(15)
m_lOnBits(4)?=?CLng(31)
m_lOnBits(5)?=?CLng(63)
m_lOnBits(6)?=?CLng(127)
m_lOnBits(7)?=?CLng(255)
m_lOnBits(8)?=?CLng(511)
m_lOnBits(9)?=?CLng(1023)
m_lOnBits(10)?=?CLng(2047)
m_lOnBits(11)?=?CLng(4095)
m_lOnBits(12)?=?CLng(8191)
m_lOnBits(13)?=?CLng(16383)
m_lOnBits(14)?=?CLng(32767)
m_lOnBits(15)?=?CLng(65535)
m_lOnBits(16)?=?CLng(131071)
m_lOnBits(17)?=?CLng(262143)
m_lOnBits(18)?=?CLng(524287)
m_lOnBits(19)?=?CLng(1048575)
m_lOnBits(20)?=?CLng(2097151)
m_lOnBits(21)?=?CLng(4194303)
m_lOnBits(22)?=?CLng(8388607)
m_lOnBits(23)?=?CLng(16777215)
m_lOnBits(24)?=?CLng(33554431)
m_lOnBits(25)?=?CLng(67108863)
m_lOnBits(26)?=?CLng(134217727)
m_lOnBits(27)?=?CLng(268435455)
m_lOnBits(28)?=?CLng(536870911)
m_lOnBits(29)?=?CLng(1073741823)
m_lOnBits(30)?=?CLng(2147483647)
m_l2Power(0)?=?CLng(1)
m_l2Power(1)?=?CLng(2)
m_l2Power(2)?=?CLng(4)
m_l2Power(3)?=?CLng(8)
m_l2Power(4)?=?CLng(16)
m_l2Power(5)?=?CLng(32)
m_l2Power(6)?=?CLng(64)
m_l2Power(7)?=?CLng(128)
m_l2Power(8)?=?CLng(256)
m_l2Power(9)?=?CLng(512)
m_l2Power(10)?=?CLng(1024)
m_l2Power(11)?=?CLng(2048)
m_l2Power(12)?=?CLng(4096)
m_l2Power(13)?=?CLng(8192)
m_l2Power(14)?=?CLng(16384)
m_l2Power(15)?=?CLng(32768)
m_l2Power(16)?=?CLng(65536)
m_l2Power(17)?=?CLng(131072)
m_l2Power(18)?=?CLng(262144)
m_l2Power(19)?=?CLng(524288)
m_l2Power(20)?=?CLng(1048576)
m_l2Power(21)?=?CLng(2097152)
m_l2Power(22)?=?CLng(4194304)
m_l2Power(23)?=?CLng(8388608)
m_l2Power(24)?=?CLng(16777216)
m_l2Power(25)?=?CLng(33554432)
m_l2Power(26)?=?CLng(67108864)
m_l2Power(27)?=?CLng(134217728)
m_l2Power(28)?=?CLng(268435456)
m_l2Power(29)?=?CLng(536870912)
m_l2Power(30)?=?CLng(1073741824)
Dim?x
Dim?k
Dim?AA
Dim?BB
Dim?CC
Dim?DD
Dim?a
Dim?b
Dim?c
Dim?d
Const?S11?=?7
Const?S12?=?12
Const?S13?=?17
Const?S14?=?22
Const?S21?=?5
Const?S22?=?9
Const?S23?=?14
Const?S24?=?20
Const?S31?=?4
Const?S32?=?11
Const?S33?=?16
Const?S34?=?23
Const?S41?=?6
Const?S42?=?10
Const?S43?=?15
Const?S44?=?21
x?=?ConvertToWordArray(sMessage)
a?=?&H67452301
b?=?&HEFCDAB89
c?=?&H98BADCFE
d?=?&H10325476
For?k?=?0?To?UBound(x)?Step?16
AA?=?a
BB?=?b
CC?=?c
DD?=?d
md5_FF?a,?b,?c,?d,?x(k?+?0),?S11,?&HD76AA478
md5_FF?d,?a,?b,?c,?x(k?+?1),?S12,?&HE8C7B756
md5_FF?c,?d,?a,?b,?x(k?+?2),?S13,?&H242070DB
md5_FF?b,?c,?d,?a,?x(k?+?3),?S14,?&HC1BDCEEE
md5_FF?a,?b,?c,?d,?x(k?+?4),?S11,?&HF57C0FAF
md5_FF?d,?a,?b,?c,?x(k?+?5),?S12,?&H4787C62A
md5_FF?c,?d,?a,?b,?x(k?+?6),?S13,?&HA8304613
md5_FF?b,?c,?d,?a,?x(k?+?7),?S14,?&HFD469501
md5_FF?a,?b,?c,?d,?x(k?+?8),?S11,?&H698098D8
md5_FF?d,?a,?b,?c,?x(k?+?9),?S12,?&H8B44F7AF
md5_FF?c,?d,?a,?b,?x(k?+?10),?S13,?&HFFFF5BB1
md5_FF?b,?c,?d,?a,?x(k?+?11),?S14,?&H895CD7BE
md5_FF?a,?b,?c,?d,?x(k?+?12),?S11,?&H6B901122
md5_FF?d,?a,?b,?c,?x(k?+?13),?S12,?&HFD987193
md5_FF?c,?d,?a,?b,?x(k?+?14),?S13,?&HA679438E
md5_FF?b,?c,?d,?a,?x(k?+?15),?S14,?&H49B40821
md5_GG?a,?b,?c,?d,?x(k?+?1),?S21,?&HF61E2562
md5_GG?d,?a,?b,?c,?x(k?+?6),?S22,?&HC040B340
md5_GG?c,?d,?a,?b,?x(k?+?11),?S23,?&H265E5A51
md5_GG?b,?c,?d,?a,?x(k?+?0),?S24,?&HE9B6C7AA
md5_GG?a,?b,?c,?d,?x(k?+?5),?S21,?&HD62F105D
md5_GG?d,?a,?b,?c,?x(k?+?10),?S22,?&H2441453
md5_GG?c,?d,?a,?b,?x(k?+?15),?S23,?&HD8A1E681
md5_GG?b,?c,?d,?a,?x(k?+?4),?S24,?&HE7D3FBC8
md5_GG?a,?b,?c,?d,?x(k?+?9),?S21,?&H21E1CDE6
md5_GG?d,?a,?b,?c,?x(k?+?14),?S22,?&HC33707D6
md5_GG?c,?d,?a,?b,?x(k?+?3),?S23,?&HF4D50D87
md5_GG?b,?c,?d,?a,?x(k?+?8),?S24,?&H455A14ED
md5_GG?a,?b,?c,?d,?x(k?+?13),?S21,?&HA9E3E905
md5_GG?d,?a,?b,?c,?x(k?+?2),?S22,?&HFCEFA3F8
md5_GG?c,?d,?a,?b,?x(k?+?7),?S23,?&H676F02D9
md5_GG?b,?c,?d,?a,?x(k?+?12),?S24,?&H8D2A4C8A
md5_HH?a,?b,?c,?d,?x(k?+?5),?S31,?&HFFFA3942
md5_HH?d,?a,?b,?c,?x(k?+?8),?S32,?&H8771F681
md5_HH?c,?d,?a,?b,?x(k?+?11),?S33,?&H6D9D6122
md5_HH?b,?c,?d,?a,?x(k?+?14),?S34,?&HFDE5380C
md5_HH?a,?b,?c,?d,?x(k?+?1),?S31,?&HA4BEEA44
md5_HH?d,?a,?b,?c,?x(k?+?4),?S32,?&H4BDECFA9
md5_HH?c,?d,?a,?b,?x(k?+?7),?S33,?&HF6BB4B60
md5_HH?b,?c,?d,?a,?x(k?+?10),?S34,?&HBEBFBC70
md5_HH?a,?b,?c,?d,?x(k?+?13),?S31,?&H289B7EC6
md5_HH?d,?a,?b,?c,?x(k?+?0),?S32,?&HEAA127FA
md5_HH?c,?d,?a,?b,?x(k?+?3),?S33,?&HD4EF3085
md5_HH?b,?c,?d,?a,?x(k?+?6),?S34,?&H4881D05
md5_HH?a,?b,?c,?d,?x(k?+?9),?S31,?&HD9D4D039
md5_HH?d,?a,?b,?c,?x(k?+?12),?S32,?&HE6DB99E5
md5_HH?c,?d,?a,?b,?x(k?+?15),?S33,?&H1FA27CF8
md5_HH?b,?c,?d,?a,?x(k?+?2),?S34,?&HC4AC5665
md5_II?a,?b,?c,?d,?x(k?+?0),?S41,?&HF4292244
md5_II?d,?a,?b,?c,?x(k?+?7),?S42,?&H432AFF97
md5_II?c,?d,?a,?b,?x(k?+?14),?S43,?&HAB9423A7
md5_II?b,?c,?d,?a,?x(k?+?5),?S44,?&HFC93A039
md5_II?a,?b,?c,?d,?x(k?+?12),?S41,?&H655B59C3
md5_II?d,?a,?b,?c,?x(k?+?3),?S42,?&H8F0CCC92
md5_II?c,?d,?a,?b,?x(k?+?10),?S43,?&HFFEFF47D
md5_II?b,?c,?d,?a,?x(k?+?1),?S44,?&H85845DD1
md5_II?a,?b,?c,?d,?x(k?+?8),?S41,?&H6FA87E4F
md5_II?d,?a,?b,?c,?x(k?+?15),?S42,?&HFE2CE6E0
md5_II?c,?d,?a,?b,?x(k?+?6),?S43,?&HA3014314
md5_II?b,?c,?d,?a,?x(k?+?13),?S44,?&H4E0811A1
md5_II?a,?b,?c,?d,?x(k?+?4),?S41,?&HF7537E82
md5_II?d,?a,?b,?c,?x(k?+?11),?S42,?&HBD3AF235
md5_II?c,?d,?a,?b,?x(k?+?2),?S43,?&H2AD7D2BB
md5_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
If?stype?=?32?Then
MD5?=?LCase(WordToHex(a)?&?WordToHex(b)?&?WordToHex(c)?&?WordToHex(d))
Else
MD5?=?LCase(WordToHex(b)?&?WordToHex(c))
End?If
End?Function
'下面是測試代碼
Sub?test()
MsgBox?MD5("a",?16)?'16位加密
MsgBox?MD5("a",?32)?'32位加密
End?Sub