Heartbeat Demo



Alicia has a Heart Monitor device that measures her heart rate and outputs this data in encrypted form. Since Alicia knows that she may want to share this data in the future, she uses NuCypher to create a policy public key for her Heart Monitor to use, so she can read and delegate access to the encrypted data as she sees fit.

The Heart Monitor uses this public key to produce a file with some amount of encrypted heart rate measurements. This file is uploaded to a storage layer (e.g., IPFS, S3, or whatever you choose).

At some future point, she wants to share this information with other people, such as her Doctor. Once she obtains her Doctor’s public keys, she can create a policy in the NuCypher network granting access to him. After this, her Doctor can read the file with encrypted data (which was uploaded by the Heart Monitor) and request a re-encrypted ciphertext for each measurement, which can be opened with the Doctor’s private key.

This simple example showcases many interesting and distinctive aspects of NuCypher:

  • Alicia can create policy public keys before knowing the potential consumers.

  • Alicia, or anyone knowing the policy public key (e.g., the Heart Monitor), can produce encrypted data that belongs to the policy. Again, this can happen before granting access to any consumer.

  • As a consequence of the previous point, the Heart Monitor is completely unaware of the recipients. In its mind, it’s producing data for Alicia.

  • Alicia never interacts with the Doctor: she only needs the Doctor’s public keys.

  • Alicia only interacts with the NuCypher network for granting access to the Doctor. After this, she can even disappear from the face of the Earth.

  • The Doctor never interacts with Alicia or the Heart Monitor: he only needs the encrypted data and some policy metadata.

The NuCypher Characters

The actors in this example can be mapped naturally to Characters in the NuCypher narrative:

  • Since Alicia is the only one capable of granting access, she retains full control over the data encrypted for her. As such, she can be considered as the data owner or the policy authority. This corresponds to the Alice character.

  • The Heart Monitor, or any other data sources that encrypt data on Alicia’s behalf, is portrayed by the Enrico character.

  • Nodes in the NuCypher network are called Ursula in our terminology. They receive the access policy from Alice and stand ready to re-encrypt data in exchange for payment in fees and token rewards. In a way, they enforce the access policy created by Alicia.

  • The Doctor acts as a data recipient, and only can decrypt Alicia’s data if she grants access to him. This is modelled by the Bob character.

Install NuCypher

Acquire the nucypher application code and install the dependencies:

$ git clone https://github.com/nucypher/nucypher.git
$ python -m venv nucypher-venv
$ source nucypher-venv/bin/activate
(nucypher-venv)$ cd nucypher
(nucypher-venv)$ pip install -e .

Run the Demo

Assuming you already have nucypher installed with the demos extra, running the Heartbeat demo involves running a local fleet of federated Ursulas in the examples/ directory, and executing the alicia.py and doctor.py scripts contained in the examples/heartbeat_demo directory.

First, run the local fleet of federated Ursulas in a separate terminal:

(nucypher)$ python examples/run_demo_ursula_fleet.py

This provides a network of 12 local federated Ursulas.

Next, from the examples/heartbeat_demo directory, run alicia.py:

(nucypher)$ python alicia.py

This will create a temporal directory called alicia-files that contains the data for making Alicia persistent (i.e., her private keys). Apart from that, it will also generate data and keys for the demo. What’s left is running the doctor.py script:

(nucypher)$ python doctor.py

This script will read the data generated in the previous step and retrieve re-encrypted ciphertexts by means of the NuCypher network. The result is printed in the console:

Creating the Doctor ...
Doctor =  ⇀Maroon Snowman DarkSlateGray Bishop↽ (0xA36bcd5c5Cfa0C1119ea5E53621720a0C1a610F5)
The Doctor joins policy for label 'heart-data-❤️-e917d959'
----------------------❤︎ (82 BPM)                    Retrieval time:  3537.06 ms
---------------------❤︎ (81 BPM)                     Retrieval time:  2654.51 ms
-------------------------❤︎ (85 BPM)                 Retrieval time:  1513.32 ms
----------------------------❤︎ (88 BPM)              Retrieval time:  1552.66 ms
-----------------------❤︎ (83 BPM)                   Retrieval time:  1720.66 ms
---------------------❤︎ (81 BPM)                     Retrieval time:  1485.25 ms
---------------------❤︎ (81 BPM)                     Retrieval time:  1459.16 ms
---------------------❤︎ (81 BPM)                     Retrieval time:  1520.30 ms
----------------❤︎ (76 BPM)                          Retrieval time:  1479.54 ms
----------------❤︎ (76 BPM)                          Retrieval time:  1464.17 ms
---------------------❤︎ (81 BPM)                     Retrieval time:  1483.04 ms
----------------❤︎ (76 BPM)                          Retrieval time:  1687.72 ms
---------------❤︎ (75 BPM)                           Retrieval time:  1563.65 ms