Django template tag for MailHide. Based on http://iamtgc.com/recaptcha-mailhide-template-filter-for-django/

Django MailHide Template Tag

import base64
import binascii
from Crypto.Cipher import AES

from django.template import Library
from django.utils.safestring import mark_safe 
from django.conf import settings


register = Library()


@register.simple_tag
def mailhide(email, **kwargs):
    """Tag to disguse an email address using the reCaptcha's Mailhide service"""
    if not email or '@' not in email:
        return u''
    numpad = 16 - (len(email) % 16)
    padded_value = email + numpad * chr(numpad)
    key = binascii.unhexlify(settings.MAILHIDE_PRIVATE_KEY)
    obj = AES.new(key, AES.MODE_CBC, '\000' * 16)
    encrypted_value = obj.encrypt(padded_value)
    fmt_args = {
        'public_key': settings.MAILHIDE_PUBLIC_KEY,
        'encrypted_email': base64.urlsafe_b64encode(encrypted_value)
    }
    display_string = kwargs.pop('display_string', None)
    if not display_string:
        display_string = u'...@' % value[value.index('@') + 1:]
    fmt_args['display_string'] = display_string
    return mark_safe(u'''<a href="http://mailhide.recaptcha.net/d?k=%(public_key)s&amp;c=%(encrypted_email)s"
                            onclick="window.open('http://mailhide.recaptcha.net/d?k=%(public_key)s&amp;c=%(encrypted_email)s', '',
                            'toolbar=0,scrollbars=0,location=0,statusbar=0,menubar=0,resizable=0,width=500,height=280');
                            return false;" title="Reveal this e-mail address">%(display_string)s</a>''' % fmt_args)