In question 1.3, if you send merged packets of the form <pkt1,pkt2,...,pktN,sign(key, (pkt1,pkt2,...pktN))> where "," denotes a suitable delimiter, I don't see any new DoS opportunities. Does anyone see them?
(I think the person who wrote that question wants you to send separate packets pkt1, ..., pktN and then a signature over all these packets; in this case, an attacker could disrupt the protocol by inserting a junk packet, causing the verification to fail.)
(I think the person who wrote that question wants you to send separate packets pkt1, ..., pktN and then a signature over all these packets; in this case, an attacker could disrupt the protocol by inserting a junk packet, causing the verification to fail.)