验证码的程序及原理

March 25,2004

#####  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



<%
   '### 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"

%>