is the Digest of Prepare messages is that of a replica or is it the same signature of the pre-prepare sent by the primary in PBFT?

Question

im learning PBFT From this paper osdi99 Pbft which is the original paper that proposes the protocol

after the primary sends a pre-prepare message the replicas would create a prepare message that includes a digital signature

so im wondering if this digest is that of a replica or that that was included in the pre-preare Message(the primary digital signature of the client request)?

i am also confused what would happen if for example a non-faulty node would get disconnected from the network for a while ,what would he do if gets back online ?

Answer 1

I actually found the answer for those who are interested, it is actually both, so when you send any Kind message there must be wrapper around that message.

that wrapper itself contains the replica digest, and inside that wrapper you must have the preprepare message sent by the primary (in case you want to send Prepare or Commit ,in this case you need the whole preprepare message as an inner message for security reasons) , that preprepare message contains the primary digest.