Explore the possibility to use Matrix E2E keys for event signature

[GordonF42]

Riot uses device keys in order to encrypt events in E2E encrypted rooms. These keys are also able to sign events.

Can we use the Matrix key infrastructure for generating cryptographic keys and use them for signing events (without encrypting them) ?

Matrix E2E spec: https://matrix.org/speculator/spec/HEAD/client_server/unstable.html#module-e2e

[vabd]

Once that's done, we'll need to harmonise the specs in terms of signature-related event properties and add some technical details and advices on signature generation.

[vabd]

I'm wondering whether this is really needed at a specifications level. The current structure we have is good enough regardless of whether we use the Matrix SDKs to handle signing events, so surely we can go with it and decide what the implementation looks like once we start working on it?

[vabd]

Since we decided (during offline discussions) that this was implementation specific, I'm transferring this issue to the client's repo