ciao a tutti sto usando questo piccolo algoritmo per criptare e decriptare delle stringhe:

codice:



<!-- Begin
/************************************************************************
* Copyright 2001 by Terry Yuen.
* Email: kaiser40@yahoo.com
* Last update: July 15, 2001.
* To implement this script onto your page, copy and paste the Javascript
* on this page and place it in the page that you want the encryption
* routine available on. Then use the function "encrypt()" to encrypt
* data. This function takes two parameters. The first parameter is the
* plain text string and the second parameter is the key. The returned
* string is the encrypted string. To decrypt the string, use the
* function "decrypt()" with the encrypted string as the first parameter
* and key as the second parameter. It returns the decrypted string.
*
* Examples:
* var secret = encrypt("My surprise will consist of ....", "password");
* document.writeln(secret);
*
* document.form[0].elements[1].value = decrypt(document.form[0].elements[0].value, "password");
*
*************************************************************************/

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 -->
scaricato da html.

Dovrei però fargli una modifica se possibile, vorrei solo che la stringa criptata sia più lunga ma non so dove e cosa modificare!
Se qualcuno può aiutarmi!
grazie!