---
title: The Bitcoin Piñata
abstract: ![Piñata](/static/img/pinata.png)
---

![Piñata](/static/img/pinata.png)

The [Bitcoin Piñata](http://ownme.ipredator.se) is a unikernel which serves as
bug bounty system to test TLS and the underlying implementations.  Its
communication endpoints are a website describing the setup, and both a TLS
client and a TLS server listening on a port.  The total size, including TLS,
X.509, TCP/IP, of the virtual machine image is 4MB, which is less than 4% of a
comparable system using a Linux kernel and OpenSSL.

When a TLS handshake is successfully completed with mutual authentication, the
Piñata transmits the private key to a bitcoin wallet which initially contained
10BTC.  In 2018, most of them will be reused for other projects.

On startup, the Piñata generates its certificate authority on the fly, including
certificates and private keys.  This means that only the Piñata itself contains
private keys which can authenticate successfully, and an attacker has to find
an exploitable flaw in any software layer (OCaml runtime, virtual network
device, TCP/IP stack, TLS library, X.509 validation, or elsewhere) to complete the challenge.

The Piñata is online since February 2015, and even though thousands of unique IP
addresses established connections and initiated TLS handshakes, no bitcoins were
taken.  Looks like its security is decent or obscure enough.

By using a Bitcoin wallet, the Piñata is a transparent bug bounty.  Everybody
can observe (by looking into the Bitcoin blockchain) whether it has been
compromised and the money has been transferred to another wallet.  It is also
self-serving: when an attacker discovers a flaw, they don't need to fill out
any forms to retrieve the bounty, instead they can take the wallet, without any
questions asked.