Trust-Minimized Property Control with Jellybeans and Ethereum


I have a four-pound tub of jellybeans on my desk because the CEO of my company has poor impulse control.


Trusted third-parties offer compelling solutions to personal property management, but all we do is introduce a security hole. In fact, anyone who knows me knows that half the tub will be gone by the time this post is finished.

The answer is not to outsource the problem, but to remove trust-based relationships altogether. Even if the trust-based relationship is with ourselves.

Proplets — Devices for Controlling Property

Vending machines were the original smart contracts. They automatically enforce the swap of coins for snack items from the vendor.

However, vending machines require trust: The customer trusts the machine not to eat his quarters; the machine trusts the customer not to break the glass and steal the snacks.

We improve upon the original protocol by building a Jellybean machine modeled after proplets: ownership-aware devices that control tangible assets using digital protocols.


This Jellybean machine is controlled by an Ethereum client. With dynamic control code, contract terms adjust to market demand to implement surge pricing (or, in the case of my coworkers, rationing measures). The control protocol is publicly viewable on the blockchain, allowing customers to verify the behavior of the machine.

Ownership of the Jellybean machine is secured via entanglement: Deterrence mechanisms make it unfavorable to steal the machine or the jellybeans inside.

Current vending machines discourage theft by falling on their attackers. In the US, the annual risk of dying from a vending machine accident is roughly 1 in 112 million. This makes vending machines twice as deadly as sharks.

This Jellybean machine need not resort to homicide. When Athens faced a Spartan ultimatum, Pericles had his citizens burn their own property to demonstrate that they would rather self-destruct than submit. Similarly, the Jellybean machine has a bridgewire that causes it to self-immolate during attempted tampering*.

Jellybeans are a somewhat silly example of digital protocols for property control. However, it illustrates the impact of removing a simple trust-based relationship that we’ve always taken for granted. My coworkers have stopped bitching at me for picking out all the good flavors, and my blood sugar levels have stabilized because I no longer have a jellybean tub on my desk.

If you would like to buy some jellybeans, go to and follow the payment instructions.

Implementation details to follow in a future post.


*Just kidding, the machine in my office is not really going to set itself on fire. I just need my coworkers to think that. Sometimes the threat of disaster is more powerful than the actual disaster (see also: terrorism).

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