The title had to be shortened, was:

  Romantic Cryptography, i.e. how to say "I love you" but only if the other person is going to say "me too"

.. and sorry for the direct PDF link.

now i found out that the article was published in the Journal of Craptology:

  http://www.anagram.com/jcrap/Volume_7/

Truly a delightful read!

I loved the idea with the visual crypto transparencies.