I know it is not good HN policy to doubt your intentions but by emphasizing the NOT's, DEIDENTIFIED and YOU, you make me highly suspicious. Anonymization of data is difficult at best and sometimes nearly impossible so I would advise to publish the entire protocol if you want to give people assurances. The encryption key, as already stated, is pointless without an explanation how you use it and why it is employed and is otherwise just smoke and mirrors and no real security.