A Real World Attack Sample Clauses

A Real World Attack. It is widely recognized that three-pass (say, smaller-pass) protocols are favorable to the channel efficiency for authenticated key agreement. However, care must be taken for password authenticated key agreement in a practical sense. adversary server adversary server C, m −−−−→ µ, k1 Disconnect? ←−−−− C, mj −−−−→ µj, k1j Time Out? C, m −C−,−m−→j −C−,−m−→jj −−−→ µ, k1 1 ←µ−j,−k−j− 1 ←µ−jj−,−k−jj Disconnect ←−−−− Time Out or Failure Disconnect? ←−−−−− Time Out? (Count Up?)

A Real World Attack. It is widely recognized that three-pass (say, smaller-pass) protocols are favorable to the chan- nel efficiency for authenticated key agreement. However, care must be taken for password authenticated key agreement in a practical sense. N N ⟨ ⟩ ⟨ ⟩ Let us glance over Theorem 1, in advance, that is introduced in Section 4 and proved in Appendix B. There exists an adversarial advantage that is bounded by qse . The similar results can be found from the closely related work [3, 8, 26]. These advantages imply that the adversary is reduced to a simple online guessing attacker that can easily be detected and prevented from exceeding the pre-defined limit, δ, on the number of sequential on-line trials allowed by the server’s policy. For example, an adversary posing as a user C sends an arbitrary message C, m to the server, based on her guessed password. The server may respond with µ, k1 in the three-pass protocols while only µ in the four-pass protocols. Then, the adversary is assumed to check her guess with probability bounded by qse under the limit δ in three-pass protocols. Is this standard assumption really true? Unfortunately, the answer is No! This classical prevention method can be fooled out of making the adversarial advantage much larger and in some cases disclosing a password, in a surprisingly simple way. Figure 2 depicts the possible bad events. Our attack is motivated from the fact that the server is typically implemented as a multi-threaded or multi-process application for handling many user requests simultaneously, and that the three-pass password- based protocol is not an exception. As summarized in Figure 2-(a), the adversary is able to exercise the real attack (that is described in Figure 2-(b)), for example, in order to approximate the maximum amount of time the server may wait for the third message k2. The adversary then starts simultaneous authentication sessions, which the server processes independently in separate threads, and in that amount of time, is able to drive many different initiating messages based on different password guesses concurrently to the server. The adversary may get as many replies as allowed in that time boundary, by exceeding δ obviously. Figure 2-(b) abbreviates this idea. It could be a real world attack from the automated (and multi-threaded) adversary. The server instances must respond to each request and wait for the replies k2 from the adversary who can even disconnect without answering, for example, by manually unp...

A Real World Attack. It is widely recognized that three-pass (say, smaller-pass) protocols are favorable to the chan- nel efficiency for authenticated key agreement. However, care must be taken for password authenticated key agreement in a practical sense. N N