Activty & Discussion: Romeo and Juliet - An Encrypted Love Story

Credits Ali Ravi Last Updated 2013-03

In this Activity, trainers will use props and themes from the story of Shakespeare's Romeo and Juliet to help participants understand the concept of PGP encryption. Note that this Activity addresses the concept of encryption through metaphor only.

ADIDS Element

Activity and Discussion

Parent Topic(s)

PGP/GPG Email Encryption


30-45 minutes

Materials to Prepare

  • Two lockboxes that can a) be distinguished from one another; b) can be locked without their keys. Make sure you also have the keys to unlock them.
  • Index cards and tape, to affix To: and From: “Address” labels to each box.
  • Pens and/or markers
  • Assortment of small objects or photos, to place inside lockboxes

Running the Activity

Step 1: Introduction

Because of the comparatively complex nature of explaining PGP encryption using props and metaphors, we’ve outlined the basic sequence of the entire Activity here below:

  • Describe the “pre-encryption” situation.
  • Describe the public/private key pair, or private literal key & public lockbox.
  • Describe one-way aspect of encryption, Juliet getting messages from Romeo.
  • Expand into Juliet receiving from anyone, or the replicability of public lockbox.
  • Describe the reciprocal, Juliet sending messages to Romeo.
  • Expand to add “attachments” as objects sent within the public lockbox.
  • Describe how to know whose “lockbox” it actually is.

Furthermore, here are some important concept and associations to establish from the beginning, to facilitate the process and help avoid participants getting lost:

Public Key vs. Lockbox

Associate the concept of “public key” with the term “lockbox” but avoid using the word “key” initially. Later on, as the concept is being expanded, you can include the word “public” with “lockbox”.

Private Key vs. Lockbox Key

Associate the concept of “private key” with the term “lockbox key” and keep repeating the words “key” and “private” in this association to further reinforce the concept throughout.

One-Way Encryption

Start by describing “one-way encryption” (messages from Romeo to Juliet) first; then, repeat that concept, expanding to putting small photos or other items in the lockbox, before introducing the reciprocal (messages from Juliet to Romeo).

Step 2: Setting the Scene

Identify a participant as Romeo and another as Juliet. Divide the participants into two families and communities around the above participants; then, describe the situation as follows:

Romeo and Juliet are from two competing/adversarial families. They are not supposed to mingle.

Here, you can ask for someone to be a parent, another the family elder, etc.

They are both leaders of the village’s young farmers’ club.

They regularly exchange letters related to their club-work, which are constantly being read by everyone along the way.

Step 3: The Magic Lockbox

Ask Romeo to write a letter to Juliet: -Put “to:” & “from:” addresses on the envelope; -Have it be delivered to Juliet via several people in the village.

Ask the villagers to note all the information they can gather, specifically:
  • The Sender
  • The Recipient
  • The message content

Now, tell them that Romeo and Juliet fall in love, and would like to exchange personal notes, but are worried that the village will know of their affair. Then, one day, a PGP Gnome or Crypto Gnome appears in a meadow where Juliet is napping (the trainer plays this role), and provides Juliet with the following instructions and items:

“Juliet! Do you want Romeo to send you a note so that no one along the way can tell what it is? Then you should give him this, your very own open lockbox.”

Hand Juliet one of the lockboxes, and continue with:

“This is a magical lockbox - why is it magical?”
  • You have as many of the same lockbox as you want.
  • You can give it to whomever you want to have send you confidential messages.
  • Once they put their message in your lockbox and send it to you, another lockbox is magically there for them to use.
  • Once they close and lock your lockbox, only its Private key can open it.

Hand Juliet the key to the lockbox; then, continue with:

“This is your Private key. Only you have this key (hand over the key). It is yours, and it is private.”
  • Keep your private key very safe.
  • Do not lose or share your private key. It will always open this lockbox and all of its copies.
  • If you lose this private key, you will not be able to open the lockboxes associated with it again, ever.

A helpful metaphor for self-authentication via password: “the private key will imprint itself on you the first time, with your kiss. Thereafter it will only work after you kiss it to tell it that it is you who are using it and no one else. From this point on, the key will only work with your kiss.”

Step 4: The Initial Exchange

Ask Juliet to give the lockbox to Romeo at the next youth club meeting, and to then tell him what to do with it - give them a chance to articulate what the purpose of the lockbox is to Romeo. Ask Romeo to write a note to Juliet, place it in the box, put the to: & from: addresses on the outside, and send the message.

Ask the people in the village to note all the information they can collect, specifically:
  • The Sender
  • The Receiver
  • NOT the message content

Ask Juliet to open the lockbox and review the content; optionally, you can ask them if they want to share the content with the village. This step can be repeated, where the PGP Gnome/Trainer has to “magically” give back the lockbox to Romeo, for transferring other items such as photos, or small gifts (as a metaphor for email attachments).

Ask Participants:

“So what if Juliet wants the village butcher to send her something in confidence?”

Answer: Juliet gives the butcher a lockbox!

“What if Juliet wants everyone to send her confidential messages? Who can use Juliet’s lockbox?”

Answer: Anyone!

Begin associating the word “public” with the ‘lockbox’ here - Juliet can leave a lockbox in the lockbox-tree in the village (a metaphor for describing the keyserver concept). This will help to reinforce the public aspect of the lockbox.

Step 5. Romeo’s Reply

At some point after Juliet has opened, or “decrypted”, the second message with attachments, begin the next part of the story introducing Romeo’s keypair by asking questions, repeating and/or correcting as needed.

Ask Participants:

“So what if Juliet wants to send Romeo something confidental?”

Answer: Romeo will need a lockbox of his own!

“Can Juliet use her own lockbox to send something confidential to Romeo? Who is the only person who can open her lockbox?”

Answer: No, as Juliet is the only one who can open her lockbox using her private key!

“What does Romeo need to give to Juliet first before she can send him confidential messages?”

Answer: His own lockbox!

Where does Romeo get his own lockbox and private key?

Answer: the PGP-Gnome/Trainer, a metaphor for GPGTools, Enigmail, and/or other PGP keypair generating tools!

Provide Romeo with his own lockbox and key. Use this to review and repeat the concepts, associating them with the elements of PGP:

  • Public “lockbox”, which is the public key.
  • Key to the public lockbox, or the private key.
  • Self-Authentication of the Private Key with a passphrase, or “kissing the key”.
  • Replicability of the public lockbox (a person’s public key is actually a file and can be copied)
  • Announce that the software refers to the lockbox also as key, so public key = public lockbox.

Leading the Discussion

For the Discussion, pose the following questions to participants, in addition to any needed review of the concepts introduced during the Activity:

  • What happens if you lose your private key?
  • Who do you give your private key to?
  • Who can send you messages using your public lockbox?
  • Can you get a new private key for your public lockbox?
  • How many copies of the public lockbox can you have?
  • How many copies of your private key can you have? Should you have copies of your private key?