md5.bas

VB类实现学生信息管理系统

Attribute VB_Name = "md5"
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: [phone]
'         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
'