Transcript epoch versioning

[cygnusv]

Let's call "epoch" to each period with a given configuration of valid private shares (each of them held by a different node). On each successful recovery or refresh protocols, there will be a new set of valid private shares, and therefore, a new epoch.

For the moment, we don't have recovery and refresh protocols in production, so all our cohorts can only be at epoch 0, but for next releases, we will need some versioning mechanism to handle new epochs.

[piotr-roslaniec]

We could use the block number for the current epoch, similar to how Ferveo originally did.

So instead of (for example) starting at 0 and incrementing, we can compare epochs of two sets of private shares and discard the older one.