Underlying the Tezos network is a consensus algorithm, which, for the ease of reference, we will call Emmy. Consensus ensures that participants agree on the same blockchain and on its state. The ideas behind Emmy are described in the white paper and the specifics to its implementation can be found in the documentation. We recall that Emmy is a PoS based consensus with a use of endorsements to speed-up confirmation times and reduce selfish baking. This was done by defining the chain fitness as the total number of endorsements (in addition to the chain length).
This post introduces Emmy+, an improvement of Emmy which still guards against selfish baking but also achieves greater efficiency and stability. Emmy+ will be included in our next protocol proposal.
The main difference is that, in Emmy+, the number of endorsements included in a block no longer influences the fitness, but the timing of a block: the fewer endorsements a block carries the longer it takes before it can be considered valid. More precisely, a block is valid only if its timestamp has a minimal delay with respect to the previous block’s timestamp, and this minimal delay depends not only on the block’s priority but also on the number of endorsement operations included in the block.
As for block fitness, in Emmy+, it increases by one unit with each level. In this way, Emmy+ simplifies the optimal baking strategy: the bakers used to have to choose whether to wait for more endorsements to include in their block, or to publish the block immediately, without waiting. The incentive for including more endorsements was to increase the fitness and win against unknown blocks. However, when a block was produced too late in the priority period, there was the risk that the block did not reach endorsers before the block of the next priority. In Emmy+, the baker does not need to take such a decision, because the baker cannot publish a block too early. This should lead to fewer missed blocks and...