// http://www.celticproductions.net/articles/10/email/php+email+obfuscator.html
function munge($address) {
  $address = strtolower($address);
  $coded = "";
  $unmixedkey = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789@!#$%&*+-/=?_{|}~.";

  $inprogresskey = $unmixedkey;
  $mixedkey="";
  $unshuffled = strlen($unmixedkey);
  for ($i = 0; $i <= strlen($unmixedkey); $i++) {
    $ranpos = rand(0,$unshuffled-1);
    $nextchar = $inprogresskey{$ranpos};
    $mixedkey .= $nextchar;
    $before = substr($inprogresskey,0,$ranpos);
    $after = substr($inprogresskey,$ranpos+1,$unshuffled-($ranpos+1));
    $inprogresskey = $before.''.$after;
    $unshuffled -= 1;
  }
  $cipher = $mixedkey;

  $shift = strlen($address);
  for ($j=0; $j<strlen($address); $j++) {
    if (strpos($cipher,$address{$j}) == -1 ){
      $chr = $address{$j};
      $coded .= $address{$j};
    } else {
      $chr = (strpos($cipher,$address{$j}) + $shift) % strlen($cipher);
      $coded .= $cipher{$chr};
    }
  }
  return array('coded'=>$coded, 'key'=>$cipher);
}

add_action('wp_head', 'print_mail_obfuscate_js');
function print_mail_obfuscate_js() {
echo <<<EOS
<script type="text/javascript" language="javascript">
<!--
// original code is :
// http://www.celticproductions.net/articles/10/email/php+email+obfuscator.html
function mailto_obfuscate(targetid, coded, key) {
  shift=coded.length;
  link="";
  for (i=0; i<coded.length; i++) {
    if (key.indexOf(coded.charAt(i))==-1) {
      ltr = coded.charAt(i);
      link += (ltr);
    }
    else {     
      ltr = (key.indexOf(coded.charAt(i))-shift+key.length) % key.length;
      link += (key.charAt(ltr));
    }
  }

  var mailtotag = document.getElementById(targetid);
  mailtotag.setAttribute("href", "mailto:"+link);
  if (typeof mailtotag.childNodes[0] === "undefined") {
    mailtotag.appendChild(document.createTextNode(link));
  }
}
//-->
</script>
EOS;
}

function mail_obfuscate_tag_func($atts, $content="") {
  extract(shortcode_atts(array(
         'email'=>false,
         'css_class'=>"",
  ), $atts));

  if ($email) {
    $targetid="mailto-". md5(sprintf("%d:%d", get_the_ID(), time()));
    extract(munge($email));
    return "<a id=\"{$targetid}\" class=\"{$css_class}\">{$content}</a> <script type=\"text/javascript\">mailto_obfuscate('{$targetid}', '{$coded}', '{$key}' ); </script>";
  } 
  return "";
}
add_shortcode('mail_obfuscate', 'mail_obfuscate_tag_func');