tinySSB is a variation of Secure Scuttlebutt (SSB) https://scuttlebutt.nz/, a radically decentral approach of implementing distributed applications. In a nutshell, with SSB we get "social media without servers". tinySSB enabes the same, but is able to work in constraint environments thanks to its minuscule packet size of 120B.
The core of SSB are single-author append-only logs that are replicated at will and on a best-effort basis. Eventually, all updates to a log will reach the interested parties who can verify the authenticity and integrity of each update. This also applies to auxiliary forwarders, making any SSB-aware entity a potential link in the forwarding chains. Any means of replication is fine, which can be BlueTooth Low Energy, Internet protocols, USB sticks, or data printed on paper, collected and dispatched centrally or simply using a gossip protocol: anything goes!
Each append-only log is a trivial Conflict-free Replicated Data Type (CRDT). A set of append-only logs also of a CRDT. CRDTs are best understood as virtual (because distributed) data where a local site keeps a copy and can act on this copy. CRDTs are designed such that any local modification results in update messages sent to the other replicas: if these updates are ingested correctly, all replicas will converge to the same shared state, without any central entity having to intervene or help. Writing distributed applications as and with CRDTs requires careful design but has a huge reward in unbounded scallability, in applications that continue to work when the device is offline because all updates seamlessly merge into the other replicas when the device reconnects. Go decentral!
tinySSB inherits the core concepts of classic SSB i.e., the append-only logs with signed entries, the encryption suite etc. The novelty of tinySSB lies in its
- binary packet format (instead of JSON)
- “shadow packet headers” that avoid sending and storing redundant data
- the absence of “blobs” outside the append-only logs, using side chains instead
- a very simple and connectionless replication protocol.
The data packet format has been made extremely small, namely 120 Bytes. The point is to enable the use of tinySSB in challenged environments where bandwidth and storage resources are scarce.
tinySSB runs over Bluetooth Low Energy (BLE), over long-range radio (LoRA), and perhaps in the future even over shortwave in the amateur radio bands, bouncing off the ionosphere. Embedded devices are powerful enough to handle these packets and serve well as cheap forwarders.
At the higher level, the design of distributed applications over tinySSB as well as SSB is identical - it's a CRDT world.
tinySSB is used for teaching distributed programming concepts and skills at the Computer Science Bachelor and Masters level at the University of Basel.
(see the respective folders)
- Android
- ESP32
- 16 factsheets made for the dWeb camp 2024, Aug 2024: PDF
- talk for the Swiss Radio Amateur Assoc, Emergency Communication Convention, Oct 2024: PDF
