Tham khảo tài liệu 'mobile ad hoc networks applications part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 236 Mobile Ad-Hoc Networks Applications Identifying and revoking active attackers Enforcing a PLN does not address all risk-free attacks. As an illustration consider a scenario where C receives a RREQ from S to T along a path A B and relays the RREQ indicating a path Q R C instead where Q and R are fictitious nodes inserted by C. Nodes downstream of C have no reason to suspect that Q and R do not exist and B does not have access to fis and hence fio h fis Q or fiR h fio R to verify that the value fic is indeed inconsistent. Note that if C had instead advertised a path A R C with a random fic B which has access to fiA can determine that fiC h h fiA R C . Similarly if C had modified any of the fields specified by the real upstream nodes A and B then B can recognize such attempts. Thus while there are some blatant active attacks which can be easily be recognized by neighbors some subtler attacks can not. Assume that the destination receives the tainted RREQ indicating a path Q R C D E F G and a per-hop hash Pg- Assume that the actual reason for the inconsistency in the RREQ was that C had preformed an active attack. In Ariadne all that the destination can detect at this point is that the per-hop hash fiG is inconsistent. In Ariadne-DS and Ariadne-PS T can also conclude with certainty that node G exists as T can verify the HMAC signature of G . However T cannot verify the authentication appended by F as T does not access to the value fiF which had gone into the computation of the authentication appended by F . Thus T cannot even determine if the node F actually exists in the path. If T desires to determine who is responsible for perpetrating this attack it can come to several likely conclusions like i G is a malicious node and every other node in the path has been maliciously inserted by G or ii G is a good node but F may have maliciously inserted nodes A B C D E in the path or iii both G and F are good nodes and the node E may have inserted nodes A B C D in the .
