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<html xmlns="http://www.w3.org/1999/xhtml"> 
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<meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> 
<title>字符串加密</title> 
</head> 
<body> 
<SCRIPT LANGUAGE="JavaScript"> 
<!-- Begin 
function encrypt(str, pwd) { 
if(pwd == null || pwd.length <= 0) { 
alert("Please enter a password with which to encrypt the message."); 
return null; 
} 
var prand = ""; 
for(var i=0; i<pwd.length; i++) { 
prand += pwd.charCodeAt(i).toString(); 
} 
var sPos = Math.floor(prand.length / 5); 
var mult = parseInt(prand.charAt(sPos) + prand.charAt(sPos*2) + prand.charAt(sPos*3) + prand.charAt(sPos*4) + prand.charAt(sPos*5)); 
var incr = Math.ceil(pwd.length / 2); 
var modu = Math.pow(2, 31) - 1; 
if(mult < 2) { 
alert("Algorithm cannot find a suitable hash. Please choose a different password. \nPossible considerations are to choose a more complex or longer password."); 
return null; 
} 
var salt = Math.round(Math.random() * 1000000000) % 100000000; 
prand += salt; 
while(prand.length > 10) { 
prand = (parseInt(prand.substring(0, 10)) + parseInt(prand.substring(10, prand.length))).toString(); 
} 
prand = (mult * prand + incr) % modu; 
var enc_chr = ""; 
var enc_str = ""; 
for(var i=0; i<str.length; i++) { 
enc_chr = parseInt(str.charCodeAt(i) ^ Math.floor((prand / modu) * 255)); 
if(enc_chr < 16) { 
enc_str += "0" + enc_chr.toString(16); 
} else enc_str += enc_chr.toString(16); 
prand = (mult * prand + incr) % modu; 
} 
salt = salt.toString(16); 
while(salt.length < 8)salt = "0" + salt; 
enc_str += salt; 
return enc_str; 
} 

function decrypt(str, pwd) { 
if(str == null || str.length < 8) { 
alert("A salt value could not be extracted from the encrypted message because it's length is too short. The message cannot be decrypted."); 
return; 
} 
if(pwd == null || pwd.length <= 0) { 
alert("Please enter a password with which to decrypt the message."); 
return; 
} 
var prand = ""; 
for(var i=0; i<pwd.length; i++) { 
prand += pwd.charCodeAt(i).toString(); 
} 
var sPos = Math.floor(prand.length / 5); 
var mult = parseInt(prand.charAt(sPos) + prand.charAt(sPos*2) + prand.charAt(sPos*3) + prand.charAt(sPos*4) + prand.charAt(sPos*5)); 
var incr = Math.round(pwd.length / 2); 
var modu = Math.pow(2, 31) - 1; 
var salt = parseInt(str.substring(str.length - 8, str.length), 16); 
str = str.substring(0, str.length - 8); 
prand += salt; 
while(prand.length > 10) { 
prand = (parseInt(prand.substring(0, 10)) + parseInt(prand.substring(10, prand.length))).toString(); 
} 
prand = (mult * prand + incr) % modu; 
var enc_chr = ""; 
var enc_str = ""; 
for(var i=0; i<str.length; i+=2) { 
enc_chr = parseInt(parseInt(str.substring(i, i+2), 16) ^ Math.floor((prand / modu) * 255)); 
enc_str += String.fromCharCode(enc_chr); 
prand = (mult * prand + incr) % modu; 
} 
return enc_str; 
} 
// End --> 
</script> 
<form name="box"><center> 
<table cellpadding=0 cellspacing=0 border=0><tr><td colspan=3> 
<textarea cols=40 rows=5 wrap=virtual name=ipt>Welcome to baidu.com</textarea> 
</td></tr> 
<tr height=50><td valign="top"> 
<input type="button" onclick="document.box.opt.value= encrypt(document.box.ipt.value, document.box.pwd.value);" value="加密"> 
</td><td align="center" valign="center"> 
<input type="text" name="pwd" value="password"> 
</td><td align="right" valign="bottom"> 
<input type="button" onclick="document.box.ipt.value= decrypt(document.box.opt.value, document.box.pwd.value);" value="解密"> 
</td></tr> 
<tr><td colspan=3> 
<textarea cols=40 rows=5 wrap=virtual name=opt></textarea> 
</td></tr></table> 
</center> 
</form> 
</body> 

</html> 