PAD is implemented on Hyperledger Fabric, a leading permission blockchain technology. The PAD service can be accessed via API.
(See Docs for API specs and code samples).
Anyone can become a trustee and help to protect the privacy of people around the world. The easiest way to become a trustee is by deploying a Raspberry Pi.
The Pi image and instructions are also available in Docs.
We are extending the API further, and will open up direct access to the blockchain for relevant ledger transactions. We are also assessing public blockchain deployment options and expect to make further announcements on public blockchain implementations soon.