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tgroshon/Symmetric Encryption in the Old West.md

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Symmetric Encryption in the Old West.md

Symmetric Encryption in the Old West

Setup

Roles

You will need 3 teams with 1 or more people on each team (minimum 3 total people).

  • Bankers A: Dodge City
  • Bankers B: Tombstone
  • Bandits

Facilitator (narrator) can fill the role of the Bandit while the participants can be equally divided amongst the banker teams.

Materials

Required:

  1. Lockable box
  2. Two (2) padlocks with keys
  3. Loot: monopoly money, jewels, etc. to fit in a locked box
  4. Pens and scrap paper for messages

Optional fun materials:

  1. Bandit costumes: cowboy hat, bandana mask
  2. Banker costumes: top hat, suits, glasses/monocles

Story: Bandits in the Old West

The towns of Tombstone and Dodge City have banks that transfer money back and forth to eachother. Between the banks is a wilderness where a gang of Bandits live who rob wagons that travel between the towns. The bankers need to protect the money of their customers. The bank in Dodge City just bought a new safe and locks to protect the money. How can they use the safe and locks to send money to the Tombstone bank?

Activity Rounds

Setup before each round:

  1. Put each banker team on opposite sides of the room.
  2. Put bandit team in the middle of the room, halfway between the two banker teams.

Terms and Mechanics:

  • Send a message: one member of the Banker team walks a message across to the other team.
  • Send the box: one member of the Banker team walks the box it across the room to the other team.
  • Traveling banker: the banker currently transfering the box to the other team.
  • Rob the Traveling Banker: the bandit team stops the traveling banker and attempts to steal keys and loot. Set a short time limit, after which the traveling banker "escapes" with the box and key. Bandits can read messages and always steal loot and keys, but never STEAL locks or messages.
  • Deposit the loot: Once arriving at the destination bank, the other banker team must open the box and get the loot to win.
  • No "Table Talk": Nobody, especially bankers, may communicate except with written messages sent to the other team.

Round 1: The Unlocked box (Bandits Win)

Dodge City starts with loot and a box

  1. Tombstone sends a message requesting some amount of loot
  2. Dodge City team places the loot in the box
  3. Send the box to Tombstone
  4. Bandits intercept the traveling banker and steal the loot

Round 2: The Locked Box with Missing Key (Bandits Win)

Dodge City starts with loot, box, padlock, and key

  1. Tombstone sends a message requesting some amount of loot
  2. Dodge City team places the loot in the box and locks it
  3. Send the box but not the key to Tombstone
  4. Bandits rob the traveling banker; unable to steal
  5. Tombstone cannot desposit the loot because they don't have they key.

Round 3: The Locked Box with the Key (Bandits Win)

Dodge City starts with loot, box, padlock, and key

  1. Tombstone sends a message requesting some amount of loot
  2. Dodge City team places the loot in the box and locks it
  3. Send the box with key to Tombstone
  4. Bandits rob the traveling banker; steal the key and loot.

Round 4: Sending Locks (Bankers Win)

Starting state:

  • Dodge City
    • loot
    • padlock
  • Tombstone
    • box
    • padlock

Play:

  1. Dodge City sends their lock to Tombstone
  2. Tombstone fills the box with their lock and a message requesting some amount of loot
  3. Tombstone sends box to Dodge City without it's key
  4. Bandits rob the traveling banker; unable to steal
  5. Dodge City unlocks box, reads message, puts the loot inside the box and locks with Tombstone's lock
  6. Send the locked box back to Tombstone.
  7. Bandits rob the traveling banker; unable to steal
  8. Traveling banker arrives in Tombstone.
  9. Tombstone deposits the loot.

(Optional) Round 5: Reverse Reverse (Bankers Win)

Illustrates that the operation is symmetrical.

Redo Round 4 but with Banker roles reversed

Round 6: Bandits Forge Messages and Locks (Bandits Win)

Illustrates the importance of knowing who a message is from.

Rule Changes!

  1. When sending anyting, Bankers close their eyes or turn around so they can't see what happens in the middle
  2. Secret rule known only to bandits: they can steal locks

Starting state:

  • Dodge City
    • loot
    • padlock + key
  • Bandits
    • Box
    • padlock + key
  • Tombstone
    • Nothing

Play:

  1. All Bankers except traveler close their eyes.
  2. Facilitator: move one Tombstone banker to the Bandits team (he is a spy/secret bandit)
  3. Dodge City sends their lock to Tombstone
  4. Bandits steal the lock
  5. Bandits fill their own box with their lock and a message (pretending to be Tombstone) requesting all the loot
  6. Bandits lock box with Dodge City Lock and send back to Dodge City with the secret bandit
  7. Traveling banker arrives in Tombstone with nothing
  8. Secret bandit arrives in Dodge City
  9. All Bankers open their eyes.
  10. Dodge City unlocks box, reads message, puts the loot inside the box and locks with Bandits' lock
  11. Dodge City sends the locked box back to Tombstone
  12. Bandits rob the traveling banker; steal the loot
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