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Conversation

To understand the concept of conversation, we first need to understand the concept of interaction.

Interaction​

A interaction is when a set of fellows agree on a set of terms. The terms are defined by a lock template. The interaction is the result of the fellows providing each a public key to fill the placeholders in the template. A lock template where all the placeholders are filled is called a lock proposition. All interactions have a lock proposition. However, not all lock propositions are interactions.

As a side effect of having a lock proposition associated to them, interactions also have an address. This address is derived from the interaction's lock proposition.

Conversation​

A conversation is a sequence of interactions initiated by the members of a fellowship (the fellows). In a conversation, when the fellows want to spend the funds in an interaction, they provide a proof that they are the owners of the address of the interaction.

If they don't want to spend all the funds in an interaction, they need to put the change of the transaction in a new interaction.

Conversations in the brambl-cli wallet​

The brambl-cli wallet is designed to make it easy to create conversations. By default each user has a fellowship with themselves. This fellowship is called self. In the wallet, each fellowship has a unique name (like self) and a unique number.

There is also a default template included in the wallet, the default template. The default template uses the sign(0) expression. This means that the it only works with fellowships of one fellow.

In a conversation, each interaction has a number. The number of the first interaction is 1. The number of the second interaction is 2, and so on.

We have then, by default the interaction of the fellowship self with the template default and interaction number 1. When the user wants to spend some funds in the initial interaction, the wallet will create a new interaction with the same template and the number 2.

Combining the number associated with the fellowship, the template and the interaction, we have a unique triple for each interaction in the wallet. The wallet uses this triple to derive the right public and private keys to both lock the interactions and spend them.

Each user has a wallet database. The wallet database stores the fellowships, the templates and the interactions. Normally, each wallet will assign different numbers to each fellowship, template and interaction.

For example, if alice has a fellowship with bob, where they are both fellows called alice_and_bob with number 3. Bob might have a fellowship with alice, but both the name and the number in Bob's wallet database might be different.

The same happens with templates and interactions. The wallet database of each user will assign different numbers to each template and interaction.

Given a fellowship and a template, brambl-cli allows to export a base verification key to be shared with another wallet. This base verification key is used to derive the right keys to lock and spend the interactions in the shared fellowships and templates.

brambl-cli also allows to import the base verification keys of other fellows in a given fellowship in a new conversation. The conversation is identified by both the name of the fellowship and the name of the template that it uses.