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验证码的程序及原理

       ##### 版权所有 转载请保留 谢谢合作
  ##### 部分程序取自网络
  ##### 作者:扬子
  ##### Email: [email protected]
  ##### QQ: 21112856
  ##### WebSite: www.tingfo.net
  
  
  一共4个页面:form.asp; chk.asp; num.asp; count.asp
  得到一个随即数字。加密!
  解密后成成XBM图片
  利用session 判断
  
  form.asp
  
  
  <%
  '### To encrypt/decrypt include this code in your page
  '### strMyEncryptedString = EncryptString(strString)
  '### strMyDecryptedString = DeCryptString(strMyEncryptedString)
  '### You are free to use this code as long as credits remain in place
  '### also if you improve this code let me know.
  
  Private Function EncryptString(strString)
  '####################################################################
  '### Crypt Function (C) 2001 by Slavic Kozyuk [email protected] ###
  '### Arguments: strString <--- String you wish to encrypt ###
  '### Output: Encrypted HEX string ###
  '####################################################################
  
  Dim CharHexSet, intStringLen, strTemp, strRAW, i, intKey, intOffSet
  Randomize Timer
  
  intKey = Round((RND * 1000000) + 1000000) '##### Key Bitsize
  intOffSet = Round((RND * 1000000) + 1000000) '##### KeyOffSet Bitsize
  
  If IsNull(strString) = False Then
  strRAW = strString
  intStringLen = Len(strRAW)
  
  For i = 0 to intStringLen - 1
  strTemp = Left(strRAW, 1)
  strRAW = Right(strRAW, Len(strRAW) - 1)
  CharHexSet = CharHexSet & Hex(Asc(strTemp) * intKey)& Hex(intKey)
  Next
  
  EncryptString = CharHexSet & "|" & Hex(intOffSet + intKey) & "|" & Hex(intOffSet)
  Else
  EncryptString = ""
  End If
  End Function
  
  
  
  
  Private Function DeCryptString(strCryptString)
  '####################################################################
  '### Crypt Function (C) 2001 by Slavic Kozyuk [email protected] ###
  '### Arguments: Encrypted HEX stringt ###
  '### Output: Decrypted ASCII string ###
  '####################################################################
  '### Note this function uses HexConv() and get_hxno() functions ###
  '### so make sure they are not removed ###
  '####################################################################
  
  Dim strRAW, arHexCharSet, i, intKey, intOffSet, strRawKey, strHexCrypData
  
  
  strRawKey = Right(strCryptString, Len(strCryptString) - InStr(strCryptString, "|"))
  intOffSet = Right(strRawKey, Len(strRawKey) - InStr(strRawKey,"|"))
  intKey = HexConv(Left(strRawKey, InStr(strRawKey, "|") - 1)) - HexConv(intOffSet)
  strHexCrypData = Left(strCryptString, Len(strCryptString) - (Len(strRawKey) + 1))
  
  
  arHexCharSet = Split(strHexCrypData, Hex(intKey))
  
  For i=0 to UBound(arHexCharSet)
  strRAW = strRAW & Chr(HexConv(arHexCharSet(i))/intKey)
  Next
  
  DeCryptString = strRAW
  End Function
  
  
  
  Private Function HexConv(hexVar)
  Dim hxx, hxx_var, multiply
  IF hexVar <> "" THEN
  hexVar = UCASE(hexVar)
  hexVar = StrReverse(hexVar)
  DIM hx()
  REDIM hx(LEN(hexVar))
  hxx = 0
  hxx_var = 0
  FOR hxx = 1 TO LEN(hexVar)
  IF multiply = "" THEN multiply = 1
  hx(hxx) = mid(hexVar,hxx,1)
  hxx_var = (get_hxno(hx(hxx)) * multiply) + hxx_var
  multiply = (multiply * 16)
  NEXT
  hexVar = hxx_var
  HexConv = hexVar
  END IF
  End Function
  
  Private Function get_hxno(ghx)
  If ghx = "A" Then
  ghx = 10
  ElseIf ghx = "B" Then
  ghx = 11
  ElseIf ghx = "C" Then
  ghx = 12
  ElseIf ghx = "D" Then
  ghx = 13
  ElseIf ghx = "E" Then
  ghx = 14
  ElseIf ghx = "F" Then
  ghx = 15
  End If
  get_hxno = ghx
  End Function
  
  
  %>
  
  
  <%
  randomize
  num = int(7999*rnd+2000) '计数器的值
  num2 = EncryptString(num)
  session("pwdt")=num
  %>
  <form action="chk.asp" method=post>
  请输入验证码: <input type="text" name="pwds">
  <img src="count.asp?sksid=<%=num2%>"> <input type=submit value=提交>
  </form>
  
  
  chk.asp
  <%
  if trim(request.form("pwds"))<>trim(session("pwdt")) then
  %>
  输入错误: 应该为:<%=session("pwdt")%>,可你输入的是:<%=request.form("pwds")%>
  <%
  else
  %>
  输入正确
  <%end if%>
  
  count.asp
  
  <!--#include file="num.asp"-->
  
  <%
  '### To encrypt/decrypt include this code in your page
  '### strMyEncryptedString = EncryptString(strString)
  '### strMyDecryptedString = DeCryptString(strMyEncryptedString)
  '### You are free to use this code as long as credits remain in place
  '### also if you improve this code let me know.
  
  Private Function EncryptString(strString)
  '####################################################################
  '### Crypt Function (C) 2001 by Slavic Kozyuk [email protected] ###
  '### Arguments: strString <--- String you wish to encrypt ###
  '### Output: Encrypted HEX string ###
  '####################################################################
  
  Dim CharHexSet, intStringLen, strTemp, strRAW, i, intKey, intOffSet
  Randomize Timer
  
  intKey = Round((RND * 1000000) + 1000000) '##### Key Bitsize
  intOffSet = Round((RND * 1000000) + 1000000) '##### KeyOffSet Bitsize
  
  If IsNull(strString) = False Then
  strRAW = strString
  intStringLen = Len(strRAW)
  
  For i = 0 to intStringLen - 1
  strTemp = Left(strRAW, 1)
  strRAW = Right(strRAW, Len(strRAW) - 1)
  CharHexSet = CharHexSet & Hex(Asc(strTemp) * intKey)& Hex(intKey)
  Next
  
  EncryptString = CharHexSet & "|" & Hex(intOffSet + intKey) & "|" & Hex(intOffSet)
  Else
  EncryptString = ""
  End If
  End Function
  
  
  
  
  Private Function DeCryptString(strCryptString)
  '####################################################################
  '### Crypt Function (C) 2001 by Slavic Kozyuk [email protected] ###
  '### Arguments: Encrypted HEX stringt ###
  '### Output: Decrypted ASCII string ###
  '####################################################################
  '### Note this function uses HexConv() and get_hxno() functions ###
  '### so make sure they are not removed ###
  '####################################################################
  
  Dim strRAW, arHexCharSet, i, intKey, intOffSet, strRawKey, strHexCrypData
  
  
  strRawKey = Right(strCryptString, Len(strCryptString) - InStr(strCryptString, "|"))
  intOffSet = Right(strRawKey, Len(strRawKey) - InStr(strRawKey,"|"))
  intKey = HexConv(Left(strRawKey, InStr(strRawKey, "|") - 1)) - HexConv(intOffSet)
  strHexCrypData = Left(strCryptString, Len(strCryptString) - (Len(strRawKey) + 1))
  
  
  arHexCharSet = Split(strHexCrypData, Hex(intKey))
  
  For i=0 to UBound(arHexCharSet)
  strRAW = strRAW & Chr(HexConv(arHexCharSet(i))/intKey)
  Next
  
  DeCryptString = strRAW
  End Function
  
  
  
  Private Function HexConv(hexVar)
  Dim hxx, hxx_var, multiply
  IF hexVar <> "" THEN
  hexVar = UCASE(hexVar)
  hexVar = StrReverse(hexVar)
  DIM hx()
  REDIM hx(LEN(hexVar))
  hxx = 0
  hxx_var = 0
  FOR hxx = 1 TO LEN(hexVar)
  IF multiply = "" THEN multiply = 1
  hx(hxx) = mid(hexVar,hxx,1)
  hxx_var = (get_hxno(hx(hxx)) * multiply) + hxx_var
  multiply = (multiply * 16)
  NEXT
  hexVar = hxx_var
  HexConv = hexVar
  END IF
  End Function
  
  Private Function get_hxno(ghx)
  If ghx = "A" Then
  ghx = 10
  ElseIf ghx = "B" Then
  ghx = 11
  ElseIf ghx = "C" Then
  ghx = 12
  ElseIf ghx = "D" Then
  ghx = 13
  ElseIf ghx = "E" Then
  ghx = 14
  ElseIf ghx = "F" Then
  ghx = 15
  End If
  get_hxno = ghx
  End Function
  
  
  %>
  
  
  <%
  Dim Image
  Dim Width, Height
  Dim num
  Dim digtal
  Dim Length
  Dim sort
  Length = 4 '自定计数器长度
  
  Redim sort( Length )
  
  num=cint(DeCryptString(request.querystring("sksid")))
  digital = ""
  For I = 1 To Length -Len( num ) '补0
  digital = digital & "0"
  Next
  For I = 1 To Len( num )
  digital = digital & Mid( num, I, 1 )
  Next
  For I = 1 To Len( digital )
  sort(I) = Mid( digital, I, 1 )
  Next
  Width = 8 * Len( digital ) '图像的宽度
  Height = 10 '图像的高度,在本例中为固定值
  
  
  Response.ContentType="image/x-xbitmap"
  
  hc=chr(13) & chr(10)
  
  Image = "#define counter_width " & Width & hc
  Image = Image & "#define counter_height " & Height & hc
  Image = Image & "static unsigned char counter_bits[]={" & hc
  
  For I = 1 To Height
  For J = 1 To Length
  Image = Image & a(sort(J),I) & ","
  Next
  Next
  
  Image = Left( Image, Len( Image ) - 1 ) '去掉最后一个逗号
  Image = Image & "};" & hc
  %>
  <%
  Response.Write Image
  
  %>
  
  num.asp
  
  <%
  Dim a(10,10)
  
  a(0,1) = "0x3c" '数字0
  a(0,2) = "0x66"
  a(0,3) = "0xc3"
  a(0,4) = "0xc3"
  a(0,5) = "0xc3"
  a(0,6) = "0xc3"
  a(0,7) = "0xc3"
  a(0,8) = "0xc3"
  a(0,9) = "0x66"
  a(0,10)= "0x3c"
  
  a(1,1) = "0x18" '数字1
  a(1,2) = "0x1c"
  a(1,3) = "0x18"
  a(1,4) = "0x18"
  a(1,5) = "0x18"
  a(1,6) = "0x18"
  a(1,7) = "0x18"
  a(1,8) = "0x18"
  a(1,9) = "0x18"
  a(0,10)= "0x7e"
  
  
  a(2,1) = "0x3c" '数字2
  a(2,2) = "0x66"
  a(2,3) = "0x60"
  a(2,4) = "0x60"
  a(2,5) = "0x30"
  a(2,6) = "0x18"
  a(2,7) = "0x0c"
  a(2,8) = "0x06"
  a(2,9) = "0x06"
  a(2,10)= "0x7e"
  
  a(3,1) = "0x3c" '数字3
  a(3,2) = "0x66"
  a(3,3) = "0xc0"
  a(3,4) = "0x60"
  a(3,5) = "0x1c"
  a(3,6) = "0x60"
  a(3,7) = "0xc0"
  a(3,8) = "0xc0"
  a(3,9) = "0x66"
  a(3,10)= "0x38"
  
  a(4,1) = "0x38" '数字4
  a(4,2) = "0x3c"
  a(4,3) = "0x36"
  a(4,4) = "0x33"
  a(4,5) = "0x33"
  a(4,6) = "0x33"
  a(4,7) = "0xff"
  a(4,8) = "0x30"
  a(4,9) = "0x30"
  a(4,10)= "0xfe"
  
  a(5,1) = "0xfe" '数字5
  a(5,2) = "0xfe"
  a(5,3) = "0x06"
  a(5,4) = "0x06"
  a(5,5) = "0x3e"
  a(5,6) = "0x60"
  a(5,7) = "0xc0"
  a(5,8) = "0xc3"
  a(5,9) = "0x66"
  a(5,10)= "0x3c"
  
  a(6,1) = "0x60" '数字6
  a(6,2) = "0x30"
  a(6,3) = "0x18"
  a(6,4) = "0x0c"
  a(6,5) = "0x3e"
  a(6,6) = "0x63"
  a(6,7) = "0xc3"
  a(6,8) = "0xc3"
  a(6,9) = "0x66"
  a(6,10) ="0x3c"
  
  a(7,1) = "0xff" '数字7
  a(7,2) = "0xc0"
  a(7,3) = "0x60"
  a(7,4) = "0x30"
  a(7,5) = "0x18"
  a(7,6) = "0x18"
  a(7,7) = "0x18"
  a(7,8) = "0x18"
  a(7,9) = "0x18"
  a(7,10)= "0x18"
  
  a(8,1) = "0x3c" '数字8
  a(8,2) = "0x66"
  a(8,3) = "0xc3"
  a(8,4) = "0x66"
  a(8,5) = "0x3c"
  a(8,6) = "0x66"
  a(8,7) = "0xc3"
  a(8,8) = "0xc3"
  a(8,9) = "0x66"
  a(8,10)= "0x3c"
  
  a(9,1) = "0x3c" '数字9
  a(9,2) = "0x66"
  a(9,3) = "0xc3"
  a(9,4) = "0xc3"
  a(9,5) = "0x66"
  a(9,6) = "0x3c"
  a(9,7) = "0x18"
  a(9,8) = "0x0c"
  a(9,9) = "0x06"
  a(9,10)= "0x03"
  
  %>
  
  
  
  

 
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