验证码的程序及原理，看需要的人很多，就贴出来，希望进精华备查-IDC资讯中心

#####  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: yangzinet@hotmail.com
#####  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 grindkore@yahoo.com ###
     ### 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 grindkore@yahoo.com ###
     ### 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"–>

<%
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"

验证码的程序及原理，看需要的人很多，就贴出来，希望进精华备查

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