Tremola is a Secure Scuttlebutt (SSB) client for Android that only supports private chat.
Tremola aims at having the same functionality as other end-to-end encrypted messenger applications like Signal, Whatsapp or Threema but works in a decentralized way. Why is this important?
The big difference and asset over traditional end-to-end encrypted messengers is that Tremola follows SSB's decentralized approach of permissionless and trustless operations. Permissionless means that using Tremola does not depend on services provided by others (which could be turned off for you or a whole country): two Tremola-enabled smartphones can work locally even when on an island, so to speak. Trustless means that no trust is needed in auxiliary connectivity services, should you choose to use them.
Having a fully decenctralized messenger comes at a price: there is no global user directory and you must know another person's cryptographic identity beforehand, which is also known as the onboarding problem: how can you contact a peer if the peer does not know that you want to contact them nor knows your cryptographic identity? As a comparison: In case of Signal, your device's phone number is used as an identifier and Signal's servers keep track of these numbers and do the match making, while in Threema, the Threema service assigns short names on sign-up and manages them for you, also permitting you to establish contact through them if you know the peer's shortname.
Tremola solves the onboarding problem in the same way Threema works: two peers should -for trust reasons- better meet in physical space and scan a QR code on each other's smartphone to do the bonding. It is also planned that Tremola will offer a "secure wireless pairing mode" that works exactly like pairing two Bluetooth devices.
The following video shows the Tremola onboarding experience for Alice and Bob who just met in a bar and want to establish a trusted SSB channel they can use in the future. The video also shows that they can immediately test their channel via local WiFi.
Tremola is a first step towards turning SSB into a true competitor to established end-to-end encrypted messengers. On this journey, Tremola currently serves as experimentation platform both for the apps's software architecture as well as the way SSB data is handled:
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The core of SSB, namely the replication protocol and wire format, is programmed in the Kotlin language while user interface aspects and rendering is delegated to Android's WebKit module and some JavaScript (instead of hardwiring also these aspects in Kotlin).
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Tremola will follow a "surf approach" that focuses on the novelty wavefront, keeping only recent messages instead of the full history which can become quite large in SSB. This is made so that smartphones can quickly get into messaging even with peers that have accumulated a huge "append-only log".
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Tremola currently has a very limited form of secure group communications that is inherited from SSB's current protocol (limit of 7 participants, no dynamic group membership). Implementing SSB's new secure group communication protocol will be a natural evolution step for Tremola.
Crossing the Swiss alps for centuries passed through "Val Tremola", a valley on the north-south connection over the Gotthard pass. The street with the same Name still exists and is well-known for its adventurous hairpin curves. We envisage that the Tremola app also will have to do several turns until it reaches its peak.
