csha256.cls

sample login method made in visual basic

VERSION 1.0 CLASS
BEGIN
  MultiUse = -1  'True
  Persistable = 0  'NotPersistable
  DataBindingBehavior = 0  'vbNone
  DataSourceBehavior  = 0  'vbNone
  MTSTransactionMode  = 0  'NotAnMTSObject
END
Attribute VB_Name = "CSHA256"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = True
Attribute VB_PredeclaredId = False
Attribute VB_Exposed = False
'*******************************************************************************
' MODULE:       CSHA256
' FILENAME:     CSHA256.cls
' AUTHOR:       Phil Fresle
' CREATED:      10-Apr-2001
' COPYRIGHT:    Copyright 2001 Phil Fresle. All Rights Reserved.
'
' DESCRIPTION:
' This class is used to generate a SHA-256 'digest' or 'signature' of a string.
' The SHA-256 algorithm is one of the industry standard methods for generating
' digital signatures. It is generically known as a digest, digital signature,
' one-way encryption, hash or checksum algorithm. A common use for SHA-256 is
' for password encryption as it is one-way in nature, that does not mean that
' your passwords are not free from a dictionary attack. If you are using the
' routine for passwords, you can make it a little more secure by concatenating
' some known random characters to the password before you generate the signature
' and on subsequent tests, so even if a hacker knows you are using SHA-256 for
' your passwords, the random characters will make it harder to dictionary attack.
'
' *** CAUTION ***
' See the comment attached to the SHA256 method below regarding use on systems
' with different character sets.
'
' This is 'free' software with the following restrictions:
'
' You may not redistribute this code as a 'sample' or 'demo'. However, you are free
' to use the source code in your own code, but you may not claim that you created
' the sample code. It is expressly forbidden to sell or profit from this source code
' other than by the knowledge gained or the enhanced value added by your own code.
'
' Use of this software is also done so at your own risk. The code is supplied as
' is without warranty or guarantee of any kind.
'
' Should you wish to commission some derivative work based on this code provided
' here, or any consultancy work, please do not hesitate to contact us.
'
' Web Site:  http://www.frez.co.uk
' E-mail:    [e-mail]
'
' MODIFICATION HISTORY:
' 10-Apr-2001   Phil Fresle     Initial Version
'*******************************************************************************
Option Explicit

Private m_lOnBits(30)   As Long
Private m_l2Power(30)   As Long
Private K(63)           As Long

Private Const BITS_TO_A_BYTE  As Long = 8
Private Const BYTES_TO_A_WORD As Long = 4
Private Const BITS_TO_A_WORD  As Long = BYTES_TO_A_WORD * BITS_TO_A_BYTE

'*******************************************************************************
' Class_Initialize (SUB)
'*******************************************************************************
Private Sub Class_Initialize()
    ' Could have done this with a loop calculating each value, but simply
    ' assigning the values is quicker - BITS SET FROM RIGHT
    m_lOnBits(0) = 1            ' 00000000000000000000000000000001
    m_lOnBits(1) = 3            ' 00000000000000000000000000000011
    m_lOnBits(2) = 7            ' 00000000000000000000000000000111
    m_lOnBits(3) = 15           ' 00000000000000000000000000001111
    m_lOnBits(4) = 31           ' 00000000000000000000000000011111
    m_lOnBits(5) = 63           ' 00000000000000000000000000111111
    m_lOnBits(6) = 127          ' 00000000000000000000000001111111
    m_lOnBits(7) = 255          ' 00000000000000000000000011111111
    m_lOnBits(8) = 511          ' 00000000000000000000000111111111
    m_lOnBits(9) = 1023         ' 00000000000000000000001111111111
    m_lOnBits(10) = 2047        ' 00000000000000000000011111111111
    m_lOnBits(11) = 4095        ' 00000000000000000000111111111111
    m_lOnBits(12) = 8191        ' 00000000000000000001111111111111
    m_lOnBits(13) = 16383       ' 00000000000000000011111111111111
    m_lOnBits(14) = 32767       ' 00000000000000000111111111111111
    m_lOnBits(15) = 65535       ' 00000000000000001111111111111111
    m_lOnBits(16) = 131071      ' 00000000000000011111111111111111
    m_lOnBits(17) = 262143      ' 00000000000000111111111111111111
    m_lOnBits(18) = 524287      ' 00000000000001111111111111111111
    m_lOnBits(19) = 1048575     ' 00000000000011111111111111111111
    m_lOnBits(20) = 2097151     ' 00000000000111111111111111111111
    m_lOnBits(21) = 4194303     ' 00000000001111111111111111111111
    m_lOnBits(22) = 8388607     ' 00000000011111111111111111111111
    m_lOnBits(23) = 16777215    ' 00000000111111111111111111111111
    m_lOnBits(24) = 33554431    ' 00000001111111111111111111111111
    m_lOnBits(25) = 67108863    ' 00000011111111111111111111111111
    m_lOnBits(26) = 134217727   ' 00000111111111111111111111111111
    m_lOnBits(27) = 268435455   ' 00001111111111111111111111111111
    m_lOnBits(28) = 536870911   ' 00011111111111111111111111111111
    m_lOnBits(29) = 1073741823  ' 00111111111111111111111111111111
    m_lOnBits(30) = 2147483647  ' 01111111111111111111111111111111
    
    ' Could have done this with a loop calculating each value, but simply
    ' assigning the values is quicker - POWERS OF 2
    m_l2Power(0) = 1            ' 00000000000000000000000000000001
    m_l2Power(1) = 2            ' 00000000000000000000000000000010
    m_l2Power(2) = 4            ' 00000000000000000000000000000100
    m_l2Power(3) = 8            ' 00000000000000000000000000001000
    m_l2Power(4) = 16           ' 00000000000000000000000000010000
    m_l2Power(5) = 32           ' 00000000000000000000000000100000
    m_l2Power(6) = 64           ' 00000000000000000000000001000000
    m_l2Power(7) = 128          ' 00000000000000000000000010000000
    m_l2Power(8) = 256          ' 00000000000000000000000100000000
    m_l2Power(9) = 512          ' 00000000000000000000001000000000
    m_l2Power(10) = 1024        ' 00000000000000000000010000000000
    m_l2Power(11) = 2048        ' 00000000000000000000100000000000
    m_l2Power(12) = 4096        ' 00000000000000000001000000000000
    m_l2Power(13) = 8192        ' 00000000000000000010000000000000
    m_l2Power(14) = 16384       ' 00000000000000000100000000000000
    m_l2Power(15) = 32768       ' 00000000000000001000000000000000
    m_l2Power(16) = 65536       ' 00000000000000010000000000000000
    m_l2Power(17) = 131072      ' 00000000000000100000000000000000
    m_l2Power(18) = 262144      ' 00000000000001000000000000000000
    m_l2Power(19) = 524288      ' 00000000000010000000000000000000
    m_l2Power(20) = 1048576     ' 00000000000100000000000000000000
    m_l2Power(21) = 2097152     ' 00000000001000000000000000000000
    m_l2Power(22) = 4194304     ' 00000000010000000000000000000000
    m_l2Power(23) = 8388608     ' 00000000100000000000000000000000
    m_l2Power(24) = 16777216    ' 00000001000000000000000000000000
    m_l2Power(25) = 33554432    ' 00000010000000000000000000000000
    m_l2Power(26) = 67108864    ' 00000100000000000000000000000000
    m_l2Power(27) = 134217728   ' 00001000000000000000000000000000
    m_l2Power(28) = 268435456   ' 00010000000000000000000000000000
    m_l2Power(29) = 536870912   ' 00100000000000000000000000000000
    m_l2Power(30) = 1073741824  ' 01000000000000000000000000000000
    
    ' Just put together the K array once
    K(0) = &H428A2F98
    K(1) = &H71374491
    K(2) = &HB5C0FBCF
    K(3) = &HE9B5DBA5
    K(4) = &H3956C25B
    K(5) = &H59F111F1
    K(6) = &H923F82A4
    K(7) = &HAB1C5ED5
    K(8) = &HD807AA98
    K(9) = &H12835B01
    K(10) = &H243185BE
    K(11) = &H550C7DC3
    K(12) = &H72BE5D74
    K(13) = &H80DEB1FE
    K(14) = &H9BDC06A7
    K(15) = &HC19BF174
    K(16) = &HE49B69C1
    K(17) = &HEFBE4786
    K(18) = &HFC19DC6
    K(19) = &H240CA1CC
    K(20) = &H2DE92C6F
    K(21) = &H4A7484AA
    K(22) = &H5CB0A9DC
    K(23) = &H76F988DA
    K(24) = &H983E5152
    K(25) = &HA831C66D
    K(26) = &HB00327C8
    K(27) = &HBF597FC7
    K(28) = &HC6E00BF3
    K(29) = &HD5A79147
    K(30) = &H6CA6351
    K(31) = &H14292967
    K(32) = &H27B70A85
    K(33) = &H2E1B2138
    K(34) = &H4D2C6DFC
    K(35) = &H53380D13
    K(36) = &H650A7354
    K(37) = &H766A0ABB
    K(38) = &H81C2C92E
    K(39) = &H92722C85
    K(40) = &HA2BFE8A1
    K(41) = &HA81A664B
    K(42) = &HC24B8B70
    K(43) = &HC76C51A3
    K(44) = &HD192E819
    K(45) = &HD6990624
    K(46) = &HF40E3585
    K(47) = &H106AA070
    K(48) = &H19A4C116
    K(49) = &H1E376C08
    K(50) = &H2748774C
    K(51) = &H34B0BCB5
    K(52) = &H391C0CB3
    K(53) = &H4ED8AA4A
    K(54) = &H5B9CCA4F
    K(55) = &H682E6FF3
    K(56) = &H748F82EE
    K(57) = &H78A5636F
    K(58) = &H84C87814
    K(59) = &H8CC70208
    K(60) = &H90BEFFFA
    K(61) = &HA4506CEB
    K(62) = &HBEF9A3F7
    K(63) = &HC67178F2
End Sub

'*******************************************************************************
' LShift (FUNCTION)
'
' PARAMETERS:
' (In) - lValue     - Long    - The value to be shifted
' (In) - iShiftBits - Integer - The number of bits to shift the value by
'
' RETURN VALUE:
' Long - The shifted long integer
'
' DESCRIPTION:
' A left shift takes all the set binary bits and moves them left, in-filling
' with zeros in the vacated bits on the right. This function is equivalent to
' the << operator in Java and C++
'*******************************************************************************
Private Function LShift(ByVal lValue As Long, _
                        ByVal iShiftBits As Integer) As Long
    ' NOTE: If you can guarantee that the Shift parameter will be in the
    ' range 1 to 30 you can safely strip of this first nested if structure for
    ' speed.
    '
    ' A shift of zero is no shift at all.
    If iShiftBits = 0 Then
        LShift = lValue
        Exit Function
        
    ' A shift of 31 will result in the right most bit becoming the left most
    ' bit and all other bits being cleared
    ElseIf iShiftBits = 31 Then
        If lValue And 1 Then
            LShift = &H80000000
        Else
            LShift = 0
        End If
        Exit Function
        
    ' A shift of less than zero or more than 31 is undefined
    ElseIf iShiftBits < 0 Or iShiftBits > 31 Then
        Err.Raise 6
    End If
    
    ' If the left most bit that remains will end up in the negative bit
    ' position (&H80000000) we would end up with an overflow if we took the
    ' standard route. We need to strip the left most bit and add it back
    ' afterwards.
    If (lValue And m_l2Power(31 - iShiftBits)) Then
    
        ' (Value And OnBits(31 - (Shift + 1))) chops off the left most bits that
        ' we are shifting into, but also the left most bit we still want as this
        ' is going to end up in the negative bit marker position (&H80000000).
        ' After the multiplication/shift we Or the result with &H80000000 to
        ' turn the negative bit on.
        LShift = ((lValue And m_lOnBits(31 - (iShiftBits + 1))) * _
            m_l2Power(iShiftBits)) Or &H80000000
    
    Else
    
        ' (Value And OnBits(31-Shift)) chops off the left most bits that we are
        ' shifting into so we do not get an overflow error when we do the
        ' multiplication/shift
        LShift = ((lValue And m_lOnBits(31 - iShiftBits)) * _
            m_l2Power(iShiftBits))
        
    End If
End Function

'*******************************************************************************
' RShift (FUNCTION)
'
' PARAMETERS:
' (In) - lValue     - Long    - The value to be shifted
' (In) - iShiftBits - Integer - The number of bits to shift the value by
'
' RETURN VALUE:
' Long - The shifted long integer
'
' DESCRIPTION:
' The right shift of an unsigned long integer involves shifting all the set bits
' to the right and in-filling on the left with zeros. This function is
' equivalent to the >>> operator in Java or the >> operator in C++ when used on
' an unsigned long.
'*******************************************************************************
Private Function RShift(ByVal lValue As Long, _
                        ByVal iShiftBits As Integer) As Long
    
    ' NOTE: If you can guarantee that the Shift parameter will be in the
    ' range 1 to 30 you can safely strip of this first nested if structure for
    ' speed.
    '
    ' A shift of zero is no shift at all
    If iShiftBits = 0 Then
        RShift = lValue
        Exit Function
        
    ' A shift of 31 will clear all bits and move the left most bit to the right
    ' most bit position
    ElseIf iShiftBits = 31 Then
        If lValue And &H80000000 Then
            RShift = 1
        Else
            RShift = 0
        End If
        Exit Function
        
    ' A shift of less than zero or more than 31 is undefined
    ElseIf iShiftBits < 0 Or iShiftBits > 31 Then
        Err.Raise 6
    End If
    
    ' We do not care about the top most bit or the final bit, the top most bit
    ' will be taken into account in the next stage, the final bit (whether it
    ' is an odd number or not) is being shifted into, so we do not give a jot
    ' about it
    RShift = (lValue And &H7FFFFFFE) \ m_l2Power(iShiftBits)
    
    ' If the top most bit (&H80000000) was set we need to do things differently
    ' as in a normal VB signed long integer the top most bit is used to indicate
    ' the sign of the number, when it is set it is a negative number, so just
    ' deviding by a factor of 2 as above would not work.
    ' NOTE: (lValue And  &H80000000) is equivalent to (lValue < 0), you could