RNG lookahead


Looking at the Cardano explorer I see that every epoch lasts 5 days (21,600 slots in an epoch, each slot 20 seconds). I recall reading that a RNG round is made at every epoch, with the output seeding the next epoch’s slot leader election.

It therefore seems that the RNG “lookahead” for slot leaders is at least 5 days. That is, we know 5 days in advance what the slot leaders will be. Isn’t 5 days a huge amount of time in regards to adaptive attacks? How was the 5-day parameter chosen?


Yes. Ouroboros Praos introduces encrypted “leader table”, so no one knows in advance who will be the leader. Only the leader in his own slot may find out that he is in fact the leader, and when he produces the block - everyone else will be able to verify that he in fact is the rightful leader for the slot and the block is valid.

Afaik, the longer the epoch - the harder it is for an adversary to maintain any forks; meaning - the easier it is for honest nodes to converge on a single common history. It is described in the main Ouroboros paper and (i might be wrong) somewhere in this presentation: