VB MD5算法函数的详细介绍

Option Explicit

'/******************************************************************************
' * Copyright (C) 2000 by Robert Hubley. *
' * All rights reserved. *
' * *
' * This software is provided ``AS IS'' and any express or implied *
' * warranties, including, but not limited to, the implied warranties of *
' * merchantability and fitness for a particular purpose, are disclaimed. *
' * In no event shall the authors be liable for any direct, indirect, *
' * incidental, special, exemplary, or consequential damages (including, but *
' * not limited to, procurement of substitute goods or services; loss of use, *
' * data, or profits; or business interruption) however caused and on any *
' * theory of liability, whether in contract, strict liability, or tort *
' * (including negligence or otherwise) arising in any way out of the use of *
' * this software, even if advised of the possibility of such damage. *
' * *
' ******************************************************************************
'
' CLASS: MD5
'
' DESCRIPTION:
' This is a class which encapsulates a set of MD5 Message Digest functions.
' MD5 algorithm produces a 128 bit digital fingerprint (signature) from an
' dataset of arbitrary length. For details see RFC 1321 (summarized below).
' This implementation is derived from the RSA Data Security, Inc. MD5 Message-Digest
' algorithm reference implementation (originally written in C)
'
' AUTHOR:
' Robert M. Hubley 12/1999
'
'
' NOTES:
' Network Working Group R. Rivest
' Request for Comments: 1321 MIT Laboratory for Computer Science
' and RSA Data Security, Inc.
' April 1992
'
'
' The MD5 Message-Digest Algorithm
'
' Summary
'
' This document describes the MD5 message-digest algorithm. The
' algorithm takes as input a message of arbitrary length and produces
' as output a 128-bit "fingerprint" or "message digest" of the input.
' It is conjectured that it is computationally infeasible to produce
' two messages having the same message digest, or to produce any
' message having a given prespecified target message digest. The MD5
' algorithm is intended for digital signature applications, where a
' large file must be "compressed" in a secure manner before being
' encrypted with a private (secret) key under a public-key cryptosystem
' such as RSA.
'
' The MD5 algorithm is designed to be quite fast on 32-bit machines. In
' addition, the MD5 algorithm does not require any large substitution
' tables; the algorithm can be coded quite compactly.
'
' The MD5 algorithm is an extension of the MD4 message-digest algorithm
' 1,2]. MD5 is slightly slower than MD4, but is more "conservative" in
' design. MD5 was designed because it was felt that MD4 was perhaps
' being adopted for use more quickly than justified by the existing
' critical review; because MD4 was designed to be exceptionally fast,
' it is "at the edge" in terms of risking successful cryptanalytic
' attack. MD5 backs off a bit, giving up a little in speed for a much
' greater likelihood of ultimate security. It incorporates some
' suggestions made by various reviewers, and contains additional
' optimizations. The MD5 algorithm is being placed in the public domain
' for review and possible adoption as a standard.
'
' RFC Author:
' Ronald L.Rivest
' Massachusetts Institute of Technology
' Laboratory for Computer Science
' NE43 -324545 Technology Square
' Cambridge, MA 02139-1986
' Phone: (617) 253-5880
' EMail: Rivest@ theory.lcs.mit.edu
'
'
'
' CHANGE HISTORY:
'
' 0.1.0 RMH 1999/12/29 Original version
'
'

'=
'= Class Constants
'=
Private Const OFFSET_4 = 4294967296#
Private Const MAXINT_4 = 2147483647

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

'
' Initialize the class
' This must be called before a digest calculation is started
'
Public Sub MD5Init()
ByteCounter = 0
State(1) = UnsignedToLong(1732584193#)
State(2) = UnsignedToLong(4023233417#)
State(3) = UnsignedToLong(2562383102#)
State(4) = UnsignedToLong(271733878#)
End Sub

'
' MD5 Final
'
Public Sub MD5Final()
Dim dblBits As Double

Dim padding(72) As Byte
Dim lngBytesBuffered As Long

padding(0) = &H80

dblBits = ByteCounter * 8

' Pad out
lngBytesBuffered = ByteCounter Mod 64
If lngBytesBuffered <= 56 Then
MD5Update 56 - lngBytesBuffered, padding
Else
MD5Update 120 - ByteCounter, padding
End If


padding(0) = UnsignedToLong(dblBits) And &HFF&
padding(1) = UnsignedToLong(dblBits) / 256 And &HFF&
padding(2) = UnsignedToLong(dblBits) / 65536 And &HFF&
padding(3) = UnsignedToLong(dblBits) / 16777216 And &HFF&
padding(4) = 0
padding(5) = 0
padding(6) = 0
padding(7) = 0

MD5Update 8, padding
End Sub

'
' Break up input stream into 64 byte chunks
'
Public Sub MD5Update(InputLen As Long, InputBuffer() As Byte)
Dim II As Integer
Dim I As Integer
Dim J As Integer
Dim K As Integer
Dim lngBufferedBytes As Long
Dim lngBufferRemaining As Long
Dim lngRem As Long

lngBufferedBytes = ByteCounter Mod 64
lngBufferRemaining = 64 - lngBufferedBytes
ByteCounter = ByteCounter + InputLen
' Use up old buffer results first
If InputLen >= lngBufferRemaining Then
For II = 0 To lngBufferRemaining - 1
ByteBuffer(lngBufferedBytes + II) = InputBuffer(II)
Next II
MD5Transform ByteBuffer

lngRem = (InputLen) Mod 64
' The transfer is a multiple of 64 lets do some transformations
For I = lngBufferRemaining To InputLen - II - lngRem Step 64
For J = 0 To 63
ByteBuffer(J) = InputBuffer(I + J)
Next J
MD5Transform ByteBuffer
Next I
lngBufferedBytes = 0
Else
I = 0
End If

' Buffer any remaining input
For K = 0 To InputLen - I - 1
ByteBuffer(lngBufferedBytes + K) = InputBuffer(I + K)
Next K

End Sub

'
' MD5 Transform
'
Private Sub MD5Transform(Buffer() As Byte)
Dim x(16) As Long
Dim a As Long
Dim b As Long
Dim c As Long
Dim d As Long

a = State(1)
b = State(2)
c = State(3)
d = State(4)

Decode 64, x, Buffer

' Round 1
FF a, b, c, d, x(0), S11, -680876936
FF d, a, b, c, x(1), S12, -389564586
FF c, d, a, b, x(2), S13, 606105819
FF b, c, d, a, x(3), S14, -1044525330
FF a, b, c, d, x(4), S11, -176418897
FF d, a, b, c, x(5), S12, 1200080426
FF c, d, a, b, x(6), S13, -1473231341
FF b, c, d, a, x(7), S14, -45705983
FF a, b, c, d, x(8), S11, 1770035416
FF d, a, b, c, x(9), S12, -1958414417
FF c, d, a, b, x(10), S13, -42063
FF b, c, d, a, x(11), S14, -1990404162
FF a, b, c, d, x(12), S11, 1804603682
FF d, a, b, c, x(13), S12, -40341101
FF c, d, a, b, x(14), S13, -1502002290
FF b, c, d, a, x(15), S14, 1236535329

' Round 2
GG a, b, c, d, x(1), S21, -165796510
GG d, a, b, c, x(6), S22, -1069501632
GG c, d, a, b, x(11), S23, 643717713
GG b, c, d, a, x(0), S24, -373897302
GG a, b, c, d, x(5), S21, -701558691
GG d, a, b, c, x(10), S22, 38016083
GG c, d, a, b, x(15), S23, -660478335
GG b, c, d, a, x(4), S24, -405537848
GG a, b, c, d, x(9), S21, 568446438
GG d, a, b, c, x(14), S22, -1019803690
GG c, d, a, b, x(3), S23, -187363961
GG b, c, d, a, x(8), S24, 1163531501
GG a, b, c, d, x(13), S21, -1444681467
GG d, a, b, c, x(2), S22, -51403784
GG c, d, a, b, x(7), S23, 1735328473
GG b, c, d, a, x(12), S24, -1926607734

' Round 3
HH a, b, c, d, x(5), S31, -378558
HH d, a, b, c, x(8), S32, -2022574463
HH c, d, a, b, x(11), S33, 1839030562
HH b, c, d, a, x(14), S34, -35309556
HH a, b, c, d, x(1), S31, -1530992060
HH d, a, b, c, x(4), S32, 1272893353
HH c, d, a, b, x(7), S33, -155497632
HH b, c, d, a, x(10), S34, -1094730640
HH a, b, c, d, x(13), S31, 681279174
HH d, a, b, c, x(0), S32, -358537222
HH c, d, a, b, x(3), S33, -722521979
HH b, c, d, a, x(6), S34, 76029189
HH a, b, c, d, x(9), S31, -640364487
HH d, a, b, c, x(12), S32, -421815835
HH c, d, a, b, x(15), S33, 530742520
HH b, c, d, a, x(2), S34, -995338651

' Round 4
II a, b, c, d, x(0), S41, -198630844
II d, a, b, c, x(7), S42, 1126891415
II c, d, a, b, x(14), S43, -1416354905
II b, c, d, a, x(5), S44, -57434055
II a, b, c, d, x(12), S41, 1700485571
II d, a, b, c, x(3), S42, -1894986606
II c, d, a, b, x(10), S43, -1051523
II b, c, d, a, x(1), S44, -2054922799
II a, b, c, d, x(8), S41, 1873313359
II d, a, b, c, x(15), S42, -30611744
II c, d, a, b, x(6), S43, -1560198380
II b, c, d, a, x(13), S44, 1309151649
II a, b, c, d, x(4), S41, -145523070
II d, a, b, c, x(11), S42, -1120210379
II c, d, a, b, x(2), S43, 718787259
II b, c, d, a, x(9), S44, -343485551


State(1) = LongOverflowAdd(State(1), a)
State(2) = LongOverflowAdd(State(2), b)
State(3) = LongOverflowAdd(State(3), c)
State(4) = LongOverflowAdd(State(4), d)

' /* Zeroize sensitive information.
'*/
' MD5_memset ((POINTER)x, 0, sizeof (x));

End Sub

Private Sub Decode(Length As Integer, OutputBuffer() As Long, InputBuffer() As Byte)
Dim intDblIndex As Integer
Dim intByteIndex As Integer
Dim dblSum As Double

intDblIndex = 0
For intByteIndex = 0 To Length - 1 Step 4
dblSum = InputBuffer(intByteIndex) + _
InputBuffer(intByteIndex + 1) * 256# + _
InputBuffer(intByteIndex + 2) * 65536# + _
InputBuffer(intByteIndex + 3) * 16777216#
OutputBuffer(intDblIndex) = UnsignedToLong(dblSum)
intDblIndex = intDblIndex + 1
Next intByteIndex
End Sub

'
' FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.
' Rotation is separate from addition to prevent recomputation.
'
Private Function FF(a As Long, _
b As Long, _
c As Long, _
d As Long, _
x As Long, _
s As Long, _
ac As Long) As Long
a = LongOverflowAdd4(a, (b And c) Or (Not (b) And d), x, ac)
a = LongLeftRotate(a, s)
a = LongOverflowAdd(a, b)
End Function

Private Function GG(a As Long, _
b As Long, _
c As Long, _
d As Long, _
x As Long, _
s As Long, _
ac As Long) As Long
a = LongOverflowAdd4(a, (b And d) Or (c And Not (d)), x, ac)
a = LongLeftRotate(a, s)
a = LongOverflowAdd(a, b)
End Function

Private Function HH(a As Long, _
b As Long, _
c As Long, _
d As Long, _
x As Long, _
s As Long, _
ac As Long) As Long
a = LongOverflowAdd4(a, b Xor c Xor d, x, ac)
a = LongLeftRotate(a, s)
a = LongOverflowAdd(a, b)
End Function

Private Function II(a As Long, _
b As Long, _
c As Long, _
d As Long, _
x As Long, _
s As Long, _
ac As Long) As Long
a = LongOverflowAdd4(a, c Xor (b Or Not (d)), x, ac)
a = LongLeftRotate(a, s)
a = LongOverflowAdd(a, b)
End Function

'
' Rotate a long to the right
'
Function LongLeftRotate(value As Long, bits As Long) As Long
Dim lngSign As Long
Dim lngI As Long
bits = bits Mod 32
If bits = 0 Then LongLeftRotate = value: Exit Function
For lngI = 1 To bits
lngSign = value And &HC0000000
value = (value And &H3FFFFFFF) * 2
value = value Or ((lngSign < 0) And 1) Or (CBool(lngSign And _
&H40000000) And &H80000000)
Next
LongLeftRotate = value
End Function

'
' Function to add two unsigned numbers together as in C.
' Overflows are ignored!
'
Private Function LongOverflowAdd(Val1 As Long, Val2 As Long) As Long
Dim lngHighWord As Long
Dim lngLowWord As Long
Dim lngOverflow As Long

lngLowWord = (Val1 And &HFFFF&) + (Val2 And &HFFFF&)
lngOverflow = lngLowWord / 65536
lngHighWord = (((Val1 And &HFFFF0000) / 65536) + ((Val2 And &HFFFF0000) / 65536) + lngOverflow) And &HFFFF&
LongOverflowAdd = UnsignedToLong((lngHighWord * 65536#) + (lngLowWord And &HFFFF&))
End Function

'
' Function to add two unsigned numbers together as in C.
' Overflows are ignored!
'
Private Function LongOverflowAdd4(Val1 As Long, Val2 As Long, val3 As Long, val4 As Long) As Long
Dim lngHighWord As Long
Dim lngLowWord As Long
Dim lngOverflow As Long

lngLowWord = (Val1 And &HFFFF&) + (Val2 And &HFFFF&) + (val3 And &HFFFF&) + (val4 And &HFFFF&)
lngOverflow = lngLowWord / 65536
lngHighWord = (((Val1 And &HFFFF0000) / 65536) + _
((Val2 And &HFFFF0000) / 65536) + _
((val3 And &HFFFF0000) / 65536) + _
((val4 And &HFFFF0000) / 65536) + _
lngOverflow) And &HFFFF&
LongOverflowAdd4 = UnsignedToLong((lngHighWord * 65536#) + (lngLowWord And &HFFFF&))
End Function

'
' Convert an unsigned double into a long
'
Private Function UnsignedToLong(value As Double) As Long
If value < 0 Or value >= OFFSET_4 Then Error 6 ' Overflow
If value <= MAXINT_4 Then
UnsignedToLong = value
Else
UnsignedToLong = value - OFFSET_4
End If
End Function

'
' Convert a long to an unsigned Double
'
Private Function LongToUnsigned(value As Long) As Double
If value < 0 Then
LongToUnsigned = value + OFFSET_4
Else
LongToUnsigned = value
End If
End Function

'使用方法

'msgbox DigestStrToHexStr("111")