标题: XBM 图片做验证码
作者: admin
日期: 2006-08-26 11:16 AM
分类: Web编程
内容: 为什么需要验证码
有效防止某个黑客对某一个特定注册用户，用特定程序暴力破解方式进行不断的登陆尝试，即防止暴力注册/穷取密码/服务器拒绝等可能影响网站正常运行的行为。
验证码的运行机制是什么
在随机产生验证码的同时生成了一Session，然后通过表单递交数据与Session中保存的验证码进行比较，正确即验证码通过，否则出错提示。
1.XBM文件
这是一个很简单的显示XBM图片的例子，数字掩码是主要。
<%@ Language=javascript %>
<%
//一个最简单的例子
//可广泛应用于计数器、时钟等任何需要动态生成图形的地方
//通过改变ContentType的值，比如改为 "image/gif"可以作出更漂亮的图形
Response.ContentType ="image/x-xbitmap";
Response.Write ("#define counter_width 8\r\n"); //图形宽
Response.Write ("#define counter_height 10\r\n");//图形高
Response.Write ("static unsigned char counter_bits[]={\r\n");
Response.Write ("0x3c,0x66,0x60,0x60,0x30,0x18,0x0c,0x06,0x06,0x7e");//2的掩码
Response.Write ("};\r\n");
%>
2.黑白XBM随机验证码（原作者：张三疯）
xbm.asp：主要作用，随机显示四位验证码，同时产生Session("validateCode")
<!--#include file="numcode.asp"-->
<%
Response.Buffer = True
With Response
.Expires = -1
.AddHeader "Pragma","no-cache"
.AddHeader "cache-ctrol","no-cache"
End With
Dim num
Randomize
num = Int(7999 * Rnd + 2000)
Session("validateCode") = num
Dim Image
Dim Width, Height
Dim digtal
Dim Length
Dim sort
Dim hc
Length = 4
hc = chr(13) & chr(10)
Redim sort(Length)
digital = ""
For I = 1 To Length - Len(num)
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)
Height = 10
Response.ContentType = "image/x-xbitmap"
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)
Image = Image & "};" & hc
Response.Write Image
%>
其中包含文件<!--#include file="numcode.asp"-->的主要内容就是数字的掩码
numcode.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"
%>
如下进行的引用，保存为img.asp
<%
yznum=trim(request.form("yznum"))
if yznum<>"" then
if int(Session("validateCode"))=int(yznum) then
response.write("true")
else
response.write("false")
end if
else
response.write("你没有输入验证码")
end if
%>
<form action=img.asp method=post>
<img src="xbm.asp">
<input name="yznum">
<input type=submit name=submit1 value=GOIT>
</form>
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