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    <br>
    <font size="+1"><font face="Times New Roman, Times, serif">Marc,<br>
        <br>
        yes, it's reasonable -- though not always practical -- to assume
        that there are pairwise secure<br>
        channels between local app, local forwarder, next forwarder,
        etc, etc, all the way to the last<br>
        hop.<br>
        <br>
        However, my apologies for this platitude, but trust is local. <br>
        The farther you get away (in trust hops) from the source, the
        less<br>
        trust there is, and more likely it becomes that someone on the
        path will be malicious.<br>
        It works the same way with humans :-)<br>
        <br>
        Cheers,<br>
        Gene<br>
        <br>
        <br>
      </font></font>
    <pre class="moz-signature" cols="72">======================
Gene Tsudik
Chancellor's Professor of Computer Science
University of California, Irvine

</pre>
    <div class="moz-cite-prefix">On 10/13/16 9:05 AM,
      <a class="moz-txt-link-abbreviated" href="mailto:Marc.Mosko@parc.com">Marc.Mosko@parc.com</a> wrote:<br>
    </div>
    <blockquote cite="mid:032EF4D1-E49C-459C-B1A2-5CEC87D693BD@parc.com"
      type="cite">
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      Doesn’t an application have a trust channel with its local
      forwarder, and the local forwarder with the next forwarder, etc.?
      <div class=""><br class="">
      </div>
      <div class="">Marc<br class="">
        <div class=""><br class="">
          <div>
            <blockquote type="cite" class="">
              <div class="">On Oct 13, 2016, at 8:50 AM, Cesar Ghali
                <<a moz-do-not-send="true"
                  href="mailto:cghali@uci.edu" class="">cghali@uci.edu</a>>
                wrote:</div>
              <br class="Apple-interchange-newline">
              <div class="">
                <div style="white-space:pre-wrap" class="">Hi Jeff,



That's right, untrusted NACKs should not be accepted in the network. In fact a pre-arranged trusted channel is an approach proposed in the paper I shared before.



Cesar</div>
                <br class="">
                <div class="gmail_quote">
                  <div dir="ltr" class="">On Thu, Oct 13, 2016 at 08:45
                    Thompson, Jeff <<a moz-do-not-send="true"
                      href="mailto:jefft0@remap.ucla.edu" class="">jefft0@remap.ucla.edu</a>>
                    wrote:<br class="">
                  </div>
                  <blockquote class="gmail_quote" style="margin:0 0 0
                    .8ex;border-left:1px #ccc solid;padding-left:1ex">
                    <div style="word-wrap: break-word; font-size: 14px;
                      font-family: Calibri, sans-serif;" class="">
                      <div class="">Hi Cesar,</div>
                      <div class=""><br class="">
                      </div>
                      <div class="">So in Junxiao’s example, the
                        microcontroller would send an unsigned network
                        Nack? Will forwarders be configured to respond
                        to an unsigned Nack which comes from the
                        (supposed) direction from any application? (I
                        had though that these network signalling
                        messages are send between forwarders on a
                        pre-arranged trusted channel.)</div>
                      <div class=""><br class="">
                      </div>
                      <div class="">- Jeff T</div>
                      <div class=""><br class="">
                      </div>
                      <span class="">
                        <div style="font-family: Calibri; font-size:
                          11pt; text-align: left; border-width: 1pt
                          medium medium; border-style: solid none none;
                          padding: 3pt 0in 0in; border-top-color:
                          rgb(181, 196, 223);" class="">
                          <span style="font-weight:bold" class="">From:
                          </span>Cesar Ghali <<a
                            moz-do-not-send="true"
                            href="mailto:cghali@uci.edu" target="_blank"
                            class="">cghali@uci.edu</a>><br class="">
                          <span style="font-weight:bold" class="">Date:
                          </span>Thursday, October 13, 2016 at 8:29:00<br
                            class="">
                          <span style="font-weight:bold" class="">To: </span>Junxiao
                          Shi <<a moz-do-not-send="true"
                            href="mailto:shijunxiao@email.arizona.edu"
                            target="_blank" class="">shijunxiao@email.arizona.edu</a>>,
                          Jeff Thompson <<a moz-do-not-send="true"
                            href="mailto:jefft0@remap.ucla.edu"
                            target="_blank" class="">jefft0@remap.ucla.edu</a>><br
                            class="">
                          <span style="font-weight:bold" class="">Cc: </span>"<a
                            moz-do-not-send="true"
                            href="mailto:ndn-interest@lists.cs.ucla.edu"
                            target="_blank" class="">ndn-interest@lists.cs.ucla.edu</a>"
                          <<a moz-do-not-send="true"
                            href="mailto:ndn-interest@lists.cs.ucla.edu"
                            target="_blank" class="">ndn-interest@lists.cs.ucla.edu</a>><br
                            class="">
                          <span style="font-weight:bold" class="">Subject:
                          </span>Re: [Ndn-interest] Sending NACKs with
                          ndn-cpp<br class="">
                        </div>
                      </span></div>
                    <div style="word-wrap: break-word; font-size: 14px;
                      font-family: Calibri, sans-serif;" class="">
                      <span class="">
                        <div class=""><br class="">
                        </div>
                        <div class="">
                          <div class="">
                            <div style="white-space:pre-wrap" class="">That's right, mixing network and application NACKs is not a good idea. From a security perspective, this separation is discussed in details in:



<a moz-do-not-send="true" href="http://ieeexplore.ieee.org/document/7288477/" target="_blank" class="">http://ieeexplore.ieee.org/document/7288477/</a>



Cesar</div>
                            <br class="">
                            <div class="gmail_quote">
                              <div dir="ltr" class="">On Wed, Oct 12,
                                2016 at 16:07 Junxiao Shi <<a
                                  moz-do-not-send="true"
                                  href="mailto:shijunxiao@email.arizona.edu"
                                  target="_blank" class="">shijunxiao@email.arizona.edu</a>>
                                wrote:<br class="">
                              </div>
                              <blockquote class="gmail_quote"
                                style="margin:0 0 0 .8ex;border-left:1px
                                #ccc solid;padding-left:1ex">
                                <div dir="ltr" class="">Hi JeffT
                                  <div class=""><br class="">
                                  </div>
                                  <div class="">I have a temperature
                                    sensor based on ESP8266
                                    microcontroller. It uses
                                    ndn-cpp-lite, connects to a remote
                                    forwarder over TCP, and acts as a
                                    producer.</div>
                                  <div class="">The ESP8266, clocked at
                                    80MHz, has limited signing
                                    capability. It can sign or verify 8
                                    ECDSA signatures per second.</div>
                                  <div class="">If Interests are
                                    arriving too fast, I want to be able
                                    to send a NetworkNack-Congestion so
                                    that the remote forwarder can
                                    forward less Interests to the
                                    sensor.</div>
                                  <div class="">An application Nack
                                    cannot fulfill this purpose because
                                    it still requires a signature.
                                    Allowing the Interests to time out
                                    increases overhead at the remote
                                    forwarder because PIT entries stay
                                    longer.</div>
                                  <div class=""><br class="">
                                  </div>
                                  <div class="">Yours, Junxiao</div>
                                </div>
                                <div dir="ltr" class="">
                                  <div class=""><br class="">
                                    <div class="gmail_extra"><br
                                        class="">
                                      <div class="gmail_quote">On Wed,
                                        Oct 12, 2016 at 10:08 AM,
                                        Thompson, Jeff <span dir="ltr"
                                          class="">
                                          <<a moz-do-not-send="true"
href="mailto:jefft0@remap.ucla.edu" target="_blank" class="">jefft0@remap.ucla.edu</a>></span>
                                        wrote:<br class="">
                                        <blockquote class="gmail_quote"
                                          style="margin:0 0 0
                                          .8ex;border-left:1px #ccc
                                          solid;padding-left:1ex">
                                          Hi Matteo.<br class="">
                                          <br class="">
                                          A NetworkNack is a ³network²
                                          nack because it is generated
                                          by a forwarder<br class="">
                                          in the network, such as NFD. A
                                          client library like ndn-cpp is
                                          meant to be<br class="">
                                          used by an application which
                                          does not generate
                                          network-level messages. It<br
                                            class="">
                                          is called a ³network² nack to
                                          distinguish from an
                                          ³application² nack. Can<br
                                            class="">
                                          you describe the situation
                                          where your application needs
                                          to generate a nack?<br
                                            class="">
                                          <br class="">
                                          - Jeff T<br class="">
                                        </blockquote>
                                      </div>
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