Hugo Peixoto

Blockstack portuguese meetup

Published on November 01, 2019

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I went to a blockstack meetup last week. I heard about it thanks to Tiago Alves, who built a couple of apps on top of it. It has block in the name, uses decentralized a lot in its description, so I binned it under “blockchain” stuff and didn’t pay much attention to it.

The meetup started with a brief description of what blockstack is, followed by a showcase of apps using blockstack built by local folks.

App mining

Before I go into further details, one thing that was mentioned is that there is a bounty of $200k per month given to the “best apps built on Blockstack”. I’m guessing this money comes from the $75 million they raised. These rewards are paid in BTC and STX (Stacks tokens). App mining, despite its name, is not a decentralized process similar to block mining. There are select reviewers assigned by Blockstack that rank existing apps according to certain criteria. Blockstack will be phasing out BTC in favor of STX.

This felt like the biggest incentive for people to build apps. Not sure what to think of this.

Blockstack architecture

They mentioned that blockstack is composed by a bunch of different services, and that their goal is not to push everything into a blockchain - only the necessary / critical information. The first app we saw on the meetup is a file hosting service, similar to firefox send. These files don’t get stored in a blockchain, for example.

The services that I remember hearing about are Blockstack auth, Gaia, and something about smart contracts that isn’t quite ready yet. Probably related to the STX tokens? Most projects seemed to rely on Auth and Gaia exclusively.

Blockstack auth

Blockstack auth seems to be a decentralized protocol to register accounts and a way for apps to have access to account information. Something like namecoin (for unique user identification) meets OAuth. Apparently, they did use namecoin at some point in the past, but have now migrated to storing this on the Bitcoin chain. Block heights from their explorer seem to match bitcoin block heights.

When an app asks for authorization, it can specify some scopes, just like OAuth. Not many scopes are available right now. Only store_write, publish_data, and email. This protocol seems to use JWT, with the ES256K algorithm. This doesn’t seem to be in standard JWT libraries, so Blockstack provides ruby and javascript libraries that implement this algorithm.

The store_write scope grants the app access to an app specific storage bucket. Storage is implemented by the Gaia protocol/service.

Blockstack Gaia

Blockstack Gaia, the storage service, seems to be independent of blockchain usage. You can host it anywhere, it is HTTP based, and URLs are in the format https://<domain>/<prefix>/store/<address>/<filename>. There is no read access control. If you know the URL, you can access the file. Writing to files requires that you have a token signed by the private key corresponding to <address> ( with a challenge which seems to be static per server).

Sharing a storage namespace between multiple users doesn’t seem to be super easy (Blockvault is trying to implement this to share password vaults). I found something regarding scoping support in authentication tokens, but the README doesn’t mention this.

Gaia doesn’t provide any guarantee of availability / resilience. It’s a simple read/write protocol on top of HTTP. You host it on your own infrastructure. They provide backend drivers for AWS S3 and Azure Blob Storage, but have documented the driver API. You can also host them in your own hard drives.

Any encryption should be done by the writer, and it’s not enforced by the servers.


Most of the developers that presented their apps mentioned that it was super easy to integrate blockstack into their apps. There are iOS, Android, and javascript SDKs which do most of the heavy lifting (including encrypting files before uploading). They seemed to be mostly focused on design and user experience. They all seemed to have the same grievances with some of Gaia limitations.

Blockstack offers gaia storage to everyone, with some limits (20 writes per second, max 5mb per file). Due to this limitation, splits files into chunks of 5mb. This makes their app available to anyone using blockstack’s storage. Having the default storage option limited to 5mb means that apps must use these limits, even if users have their own storage with higher limits. From what I could gather, Gaia does not expose these limits in their discovery endpoints, so developers can’t optimize for this.


I registered an identity and, four hours later, it showed up in their block explorer, under “Subdomain registration”. Since Blockstack is sponsoring the name registrations (if they’re stored in the bitcoin chain, there’s a cost to it), they’re probably batching registrations. My identity is Note that this is a subdomain of id.blockstack, which I assume is a top level name controlled by Blockstack, the company.

Gaia feels more like a fediverse/indieweb/self-hosting project. If there was no free hosting by blockstack, I’m not sure so many would use this. I wonder if there are any gaia service providers.

Registration taking forever doesn’t seem very good for Blockstack auth. After talking with some of the app developers, I felt like this is something that could be replaced with a IndieAuth protocol. This would mean using DNS instead of BNS. In IndieAuth, you own your own domain and use it to log in. You could also use a subdomain from an identity provider you trust (in the same way that Blockstack controls id.blockstack). Although I guess that in blockstack’s scenario, transferring a subdomain could mean that it becomes self sovereign. Apparently BNS subdomains are not stored on-chain, so I’m not sure how that works.

Most apps presented during the meetup are open source. It could be worthwhile to port the blockstack SDK to an IndieAuth implementation.