diff options
Diffstat (limited to 'paper')
| -rw-r--r-- | paper/attack-robot.pdf | bin | 0 -> 6266 bytes | |||
| -rw-r--r-- | paper/attack-robot.svg | 463 | ||||
| -rw-r--r-- | paper/ihsm_paper.tex | 94 |
3 files changed, 542 insertions, 15 deletions
diff --git a/paper/attack-robot.pdf b/paper/attack-robot.pdf Binary files differnew file mode 100644 index 0000000..543fe66 --- /dev/null +++ b/paper/attack-robot.pdf diff --git a/paper/attack-robot.svg b/paper/attack-robot.svg new file mode 100644 index 0000000..a491edd --- /dev/null +++ b/paper/attack-robot.svg @@ -0,0 +1,463 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!-- Created with Inkscape (http://www.inkscape.org/) --> + +<svg + width="118.6135mm" + height="85.444748mm" + viewBox="0 0 118.6135 85.444748" + version="1.1" + id="svg5" + sodipodi:docname="attack-robot.svg" + inkscape:version="1.1 (c4e8f9ed74, 2021-05-24)" + xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape" + xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd" + xmlns:xlink="http://www.w3.org/1999/xlink" + xmlns="http://www.w3.org/2000/svg" + xmlns:svg="http://www.w3.org/2000/svg"> + <sodipodi:namedview + id="namedview7" + pagecolor="#ffffff" + bordercolor="#666666" + borderopacity="1.0" + inkscape:pageshadow="2" + inkscape:pageopacity="0.0" + inkscape:pagecheckerboard="0" + inkscape:document-units="mm" + showgrid="false" + inkscape:snap-global="false" + inkscape:zoom="1.4142136" + inkscape:cx="225.21351" + inkscape:cy="54.093669" + inkscape:window-width="1920" + inkscape:window-height="1024" + inkscape:window-x="0" + inkscape:window-y="0" + inkscape:window-maximized="1" + inkscape:current-layer="layer1" + fit-margin-top="5" + fit-margin-left="5" + fit-margin-right="5" + fit-margin-bottom="5" /> + <defs + id="defs2"> + <rect + x="359.98044" + y="69.053543" + width="194.04721" + height="135.26814" + id="rect25216" /> + <rect + x="401.33646" + y="59.548355" + width="139.31168" + height="98.362732" + id="rect22864" /> + <rect + x="368.71024" + y="74.453217" + width="98.056488" + height="82.006744" + id="rect21370" /> + <pattern + inkscape:collect="always" + xlink:href="#Strips1_3" + id="pattern17674" + patternTransform="matrix(0.20997628,0.12451448,-0.41802153,0.70493516,99.831237,39.867125)" /> + <pattern + inkscape:collect="always" + patternUnits="userSpaceOnUse" + width="4" + height="1" + patternTransform="translate(0,0) scale(10,10)" + id="Strips1_3" + inkscape:stockid="Stripes 1:3"> + <rect + style="fill:#cc0000;stroke:none" + x="0" + y="-0.5" + width="1" + height="2" + id="rect16592" /> + </pattern> + <rect + x="359.98044" + y="69.053543" + width="194.04721" + height="135.26814" + id="rect27445" /> + <rect + x="359.98044" + y="69.053543" + width="194.04721" + height="135.26814" + id="rect27859" /> + <rect + x="359.98044" + y="69.053543" + width="194.04721" + height="135.26814" + id="rect27859-2" /> + <rect + x="359.98044" + y="69.053543" + width="194.04721" + height="135.26814" + id="rect27859-7" /> + <rect + x="359.98044" + y="69.053543" + width="194.04721" + height="135.26814" + id="rect27859-6" /> + <rect + x="359.98044" + y="69.053543" + width="194.04721" + height="135.26814" + id="rect27859-1" /> + </defs> + <g + inkscape:label="Layer 1" + inkscape:groupmode="layer" + id="layer1" + transform="translate(-30.254311,-7.5139967)"> + <path + style="fill:none;stroke:#000000;stroke-width:0.965;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:0.965, 0.965;stroke-dashoffset:0;stroke-opacity:1" + d="M 133.31448,52.882625 V 46.614226 H 120.54082" + id="path12713" + sodipodi:nodetypes="ccc" /> + <rect + style="fill:#003399;stroke-width:1;stroke-linejoin:round;stroke-dasharray:4, 4;stop-color:#000000" + id="rect31" + width="10.662453" + height="17.252211" + x="73.817886" + y="29.329372" /> + <ellipse + style="fill:#6699ff;stroke-width:1;stroke-linejoin:round;stroke-dasharray:4, 4;stop-color:#000000" + id="path55" + cx="79.149109" + cy="53.069786" + rx="13.855765" + ry="4.6185884" /> + <ellipse + style="fill:#6699ff;stroke-width:1;stroke-linejoin:round;stroke-dasharray:4, 4;stop-color:#000000" + id="path55-7" + cx="79.149109" + cy="21.26178" + rx="13.855765" + ry="4.6185884" /> + <path + style="color:#000000;fill:url(#pattern17674);stroke-linejoin:round;stroke-dasharray:4, 4;-inkscape-stroke:none" + d="m 93.004874,43.359661 c 10e-7,2.550776 -6.203437,4.618589 -13.855765,4.618589 -7.652328,0 -13.855766,-2.067813 -13.855765,-4.618589 v -9.279067 c 10e-7,2.550776 6.203438,4.618588 13.855765,4.618588 7.652327,0 13.855764,-2.067812 13.855765,-4.618588 z" + id="path55-7-6" /> + <ellipse + style="fill:#ffcc00;stroke-width:1;stroke-linejoin:round;stroke-dasharray:3.99999, 3.99999;stop-color:#000000" + id="path55-3" + cx="79.149109" + cy="77.363274" + rx="26.374798" + ry="8.7915993" /> + <path + style="fill:none;stroke:#cc0000;stroke-width:1.265;stroke-linecap:round;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1" + d="M 54.952027,75.847393 36.961772,54.454551 51.587497,39.828827 52.837643,35.163215 h 5.459365" + id="path262" + sodipodi:nodetypes="ccccc" /> + <path + style="fill:none;stroke:#cc0000;stroke-width:1.265;stroke-linecap:round;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1" + d="m 51.587497,39.828827 4.016952,2.188162 3.087632,-3.875926" + id="path264" /> + <path + style="fill:none;stroke:#cc0000;stroke-width:0.264583px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1" + d="m 51.331833,33.239445 c -2.68657,-0.969769 -4.582535,-0.902044 -6.182511,1.460654 -1.618086,2.389441 0.340442,4.649205 1.464189,7.307178 0.903228,2.136383 1.41266,4.435217 0.388035,6.009975 -1.05617,1.623241 -2.695367,2.1185 -5.274308,2.442718 -1.630479,0.20498 -2.862181,0.360967 -3.879118,1.651826 -0.589968,0.748883 -0.897981,2.318141 -0.897981,2.318141" + id="path3622" + sodipodi:nodetypes="csssssc" /> + <circle + style="fill:#cc0000;stroke:none;stroke-width:1.265;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stop-color:#000000" + id="path5297" + cx="51.488754" + cy="40.025257" + r="2.0969195" /> + <circle + style="fill:#cc0000;stroke:none;stroke-width:1.265;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stop-color:#000000" + id="circle5381" + cx="37.351231" + cy="54.811962" + r="2.0969195" /> + <g + id="g7210" + transform="matrix(0,1.1922409,-1.1922409,0,248.33096,-8.4206447)" + style="fill:#ffcc00;stroke-width:0.838757"> + <path + id="rect5641" + style="fill:#ffcc00;stroke-width:4.01018;stroke-linecap:round;stroke-linejoin:round;stop-color:#000000" + d="m 429.97266,227.56055 c -5.96767,-0.0295 -12.48274,0.88665 -19.7793,3.15429 v 61.97461 c 15.01758,4.60846 27.15999,3.02819 38.30273,0 v -61.97461 c -5.69943,-1.87261 -11.76007,-3.12082 -18.52343,-3.15429 z m -1.75,10.37109 h 2.24414 v 25.41797 h -2.24414 z m -5.81055,1.04492 h 2.24414 v 25.41797 h -2.24414 z m 11.62305,0 h 2.24218 v 25.41797 h -2.24218 z m -17.43555,2.33399 h 2.24414 v 25.41797 h -2.24414 z m 23.24609,0 h 2.24414 v 25.41797 h -2.24414 z" + transform="matrix(0,-0.26458333,0.26458333,0,-10.403218,210.05896)" /> + <path + id="rect6111" + style="fill:#ffcc00;stroke-width:1.06103;stroke-linecap:round;stroke-linejoin:round;stop-color:#000000" + d="m 70.069991,94.02773 h 0.710689 c 0.177412,2.636457 1.474716,2.084634 1.554899,0 h 0.796942 v 5.595253 h -0.695153 c -0.208773,-3.101954 -1.589566,-1.8514 -1.519101,0 h -0.848276 z" + sodipodi:nodetypes="ccccccccc" /> + <rect + style="fill:#ffcc00;stroke:none;stroke-width:1.06103;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stop-color:#000000" + id="rect7045" + width="8.5858679" + height="1.0710945" + x="63.572243" + y="96.139145" /> + </g> + <g + id="g8590" + transform="matrix(1.6227793,0,0,1.6227793,-48.776549,-55.42076)" + style="fill:#ff6600;stroke-width:0.616227"> + <rect + style="fill:#ff6600;stroke:none;stroke-width:0.779527;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stop-color:#000000" + id="rect7234" + width="12.868855" + height="6.3858981" + x="92.149086" + y="59.305691" + rx="0.7708323" + ry="0.7708323" /> + <g + id="g8386" + transform="translate(0,0.07592982)" + style="fill:#ff6600;stroke-width:0.616227"> + <path + style="fill:#ff6600;stroke:none;stroke-width:0.163043px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1" + d="m 92.728216,62.858935 h -3.78272 v -3.33134 h 0.709639 l 1.547135,1.547138 h 1.53894 z" + id="path7954" + sodipodi:nodetypes="ccccccc" /> + <use + x="0" + y="0" + xlink:href="#path7954" + id="use8302" + transform="matrix(1,0,0,-1,0,124.84542)" + width="100%" + height="100%" + style="fill:#ff6600;stroke-width:0.616227" /> + </g> + </g> + <path + style="fill:none;stroke:#6699ff;stroke-width:0.665;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1" + d="M 65.625844,52.96581 V 21.058565" + id="path9384" /> + <path + style="fill:none;stroke:#6699ff;stroke-width:0.665;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1" + d="M 92.672374,52.96581 V 21.058565" + id="path9384-6" /> + <g + id="g2844" + transform="matrix(0.87583294,0.42434778,-0.42434778,0.87583294,24.703823,-3.7780156)" + style="fill:#cc0000;stroke-width:1.02752"> + <g + id="g2249" + transform="translate(-10.957802,-4.8495503)" + style="fill:#cc0000;stroke-width:1.02752"> + <path + style="fill:#cc0000;stroke:none;stroke-width:0.271864px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1" + d="m 51.802698,27.189339 c 0.0038,-0.358372 0.08447,-0.300802 0.310004,-0.331827 0.494104,-0.06797 1.117564,-0.07823 1.480174,-0.163994 0.328415,-0.07768 0.329328,-0.264077 0.44198,-0.446063 l 8.372187,-0.146866 c 0.813022,-0.166145 0.764656,-0.644617 1.071405,-0.863087 0,0 0.184585,-0.224681 0.312419,-0.222508 0.10223,0.0017 0.230806,0.0849 0.243652,0.186331 0.07299,0.576371 0.08562,1.976868 0.08562,1.976868 z" + id="path266" + sodipodi:nodetypes="cssccssscc" /> + <use + x="0" + y="0" + xlink:href="#path266" + id="use793" + transform="matrix(1,0,0,-1,0,54.356394)" + width="100%" + height="100%" + style="fill:#cc0000;stroke-width:1.02752" /> + </g> + <path + style="fill:#cc0000;stroke:none;stroke-width:0.271864px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1" + d="m 51.074672,22.328651 h 11.293803 l -0.35065,-0.228818 h -1.302856 v -0.40726 H 59.84365 v 0.135882 h -8.813018 z" + id="path2369" + sodipodi:nodetypes="ccccccccc" /> + <use + x="0" + y="0" + xlink:href="#path2369" + id="use2617" + transform="matrix(1,0,0,-1,1.785403e-8,44.657302)" + width="100%" + height="100%" + style="fill:#cc0000;stroke-width:1.02752" /> + <g + id="g2834" + transform="translate(-2.1557979,0.20827974)" + style="fill:#cc0000;stroke-width:1.02752"> + <rect + style="fill:#cc0000;stroke:none;stroke-width:1.02752;stroke-linejoin:round;stroke-dasharray:4.11007, 4.11007;stop-color:#000000" + id="rect2748" + width="0.22969821" + height="0.6890946" + x="62.32338" + y="21.225693" /> + <rect + style="fill:#cc0000;stroke:none;stroke-width:1.02752;stroke-linejoin:round;stroke-dasharray:4.11007, 4.11007;stop-color:#000000" + id="rect2750" + width="0.6350857" + height="0.30754745" + x="62.120686" + y="21.037823" /> + </g> + </g> + <path + style="font-variation-settings:normal;opacity:1;vector-effect:none;fill:none;fill-opacity:1;stroke:#000000;stroke-width:0.965;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:0.965, 0.965;stroke-dashoffset:0;stroke-opacity:1;-inkscape-stroke:none;stop-color:#000000;stop-opacity:1" + d="M 132.95752,76.859499 H 79.367469" + id="path12828" + sodipodi:nodetypes="cc" /> + <text + xml:space="preserve" + transform="scale(0.26458333)" + id="text21368" + style="font-size:26.6667px;line-height:1.25;font-family:sans-serif;white-space:pre;shape-inside:url(#rect21370)" /> + <text + xml:space="preserve" + transform="scale(0.26458333)" + id="text22862" + style="font-size:26.6667px;line-height:1.25;font-family:sans-serif;white-space:pre;shape-inside:url(#rect22864)" /> + <g + id="g27435" + transform="translate(6.7098762,1.0448544)"> + <circle + style="font-variation-settings:normal;opacity:1;fill:#ffffff;fill-opacity:1;stroke:#000000;stroke-width:0.665;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:0;stroke-opacity:1;stop-color:#000000;stop-opacity:1" + id="path20362" + cx="114.19244" + cy="39.213848" + r="3.9914834" /> + <text + xml:space="preserve" + transform="matrix(0.26458333,0,0,0.26458333,17.624612,16.964555)" + id="text25214" + style="font-size:26.6667px;line-height:1.25;font-family:sans-serif;white-space:pre;shape-inside:url(#rect25216)"><tspan + x="359.98047" + y="93.557974" + id="tspan31831"><tspan + style="font-family:Bahnschrift;-inkscape-font-specification:Bahnschrift" + id="tspan31829">1</tspan></tspan></text> + </g> + <g + id="g27443" + transform="translate(25.351394,12.342086)"> + <circle + style="font-variation-settings:normal;opacity:1;fill:#ffffff;fill-opacity:1;stroke:#000000;stroke-width:0.665;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:0;stroke-opacity:1;stop-color:#000000;stop-opacity:1" + id="circle27437" + cx="114.19244" + cy="39.213848" + r="3.9914834" /> + <text + xml:space="preserve" + transform="matrix(0.26458333,0,0,0.26458333,17.095445,16.964555)" + id="text27441" + style="font-size:26.6667px;line-height:1.25;font-family:sans-serif;white-space:pre;shape-inside:url(#rect27445)"><tspan + x="359.98047" + y="93.557974" + id="tspan31835"><tspan + style="font-family:Bahnschrift;-inkscape-font-specification:Bahnschrift" + id="tspan31833">2</tspan></tspan></text> + </g> + <g + id="g27857" + transform="translate(-17.130934,44.420913)"> + <circle + style="font-variation-settings:normal;opacity:1;fill:#ffffff;fill-opacity:1;stroke:#000000;stroke-width:0.665;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:0;stroke-opacity:1;stop-color:#000000;stop-opacity:1" + id="circle27851" + cx="114.19244" + cy="39.213848" + r="3.9914834" /> + <text + xml:space="preserve" + transform="matrix(0.26458333,0,0,0.26458333,17.095445,16.964555)" + id="text27855" + style="font-size:26.6667px;line-height:1.25;font-family:sans-serif;white-space:pre;shape-inside:url(#rect27859)"><tspan + x="359.98047" + y="93.557974" + id="tspan31839"><tspan + style="font-family:Bahnschrift;-inkscape-font-specification:Bahnschrift" + id="tspan31837">3</tspan></tspan></text> + </g> + <g + id="g27857-9" + transform="translate(-70.974954,23.273767)"> + <circle + style="font-variation-settings:normal;opacity:1;fill:#ffffff;fill-opacity:1;stroke:#000000;stroke-width:0.665;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:0;stroke-opacity:1;stop-color:#000000;stop-opacity:1" + id="circle27851-1" + cx="114.19244" + cy="39.213848" + r="3.9914834" /> + <text + xml:space="preserve" + transform="matrix(0.26458333,0,0,0.26458333,16.70906,16.964555)" + id="text27855-2" + style="font-size:26.6667px;line-height:1.25;font-family:sans-serif;white-space:pre;shape-inside:url(#rect27859-2)"><tspan + x="359.98047" + y="93.557974" + id="tspan31843"><tspan + style="font-family:Bahnschrift;-inkscape-font-specification:Bahnschrift" + id="tspan31841">4</tspan></tspan></text> + </g> + <g + id="g27857-0" + transform="translate(-26.822028,-22.375868)"> + <circle + style="font-variation-settings:normal;opacity:1;fill:#ffffff;fill-opacity:1;stroke:#000000;stroke-width:0.665;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:0;stroke-opacity:1;stop-color:#000000;stop-opacity:1" + id="circle27851-9" + cx="114.19244" + cy="39.213848" + r="3.9914834" /> + <text + xml:space="preserve" + transform="matrix(0.26458333,0,0,0.26458333,17.095445,16.964555)" + id="text27855-3" + style="font-size:26.6667px;line-height:1.25;font-family:sans-serif;white-space:pre;shape-inside:url(#rect27859-7)"><tspan + x="359.98047" + y="93.557974" + id="tspan31847"><tspan + style="font-family:Bahnschrift;-inkscape-font-specification:Bahnschrift" + id="tspan31845">7</tspan></tspan></text> + </g> + <g + id="g27857-06" + transform="translate(-39.731146,-8.157129)"> + <circle + style="font-variation-settings:normal;opacity:1;fill:#ffffff;fill-opacity:1;stroke:#000000;stroke-width:0.665;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:0;stroke-opacity:1;stop-color:#000000;stop-opacity:1" + id="circle27851-2" + cx="114.19244" + cy="39.213848" + r="3.9914834" /> + <text + xml:space="preserve" + transform="matrix(0.26458333,0,0,0.26458333,17.095445,16.964555)" + id="text27855-6" + style="font-size:26.6667px;line-height:1.25;font-family:sans-serif;white-space:pre;shape-inside:url(#rect27859-6)"><tspan + x="359.98047" + y="93.557974" + id="tspan31851"><tspan + style="font-family:Bahnschrift;-inkscape-font-specification:Bahnschrift" + id="tspan31849">6</tspan></tspan></text> + </g> + <g + id="g27857-8" + transform="translate(-43.852246,9.3261724)"> + <circle + style="font-variation-settings:normal;opacity:1;fill:#ffffff;fill-opacity:1;stroke:#000000;stroke-width:0.665;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:0;stroke-opacity:1;stop-color:#000000;stop-opacity:1" + id="circle27851-7" + cx="114.19244" + cy="39.213848" + r="3.9914834" /> + <text + xml:space="preserve" + transform="matrix(0.26458333,0,0,0.26458333,17.095445,16.964555)" + id="text27855-9" + style="font-size:26.6667px;line-height:1.25;font-family:sans-serif;white-space:pre;shape-inside:url(#rect27859-1)"><tspan + x="359.98047" + y="93.557974" + id="tspan31855"><tspan + style="font-family:Bahnschrift;-inkscape-font-specification:Bahnschrift" + id="tspan31853">5</tspan></tspan></text> + </g> + </g> +</svg> diff --git a/paper/ihsm_paper.tex b/paper/ihsm_paper.tex index 6b6109f..e426306 100644 --- a/paper/ihsm_paper.tex +++ b/paper/ihsm_paper.tex @@ -488,19 +488,44 @@ In the sections below, we will go into detail on such attacks on IHSMs. To put t we will start with a brief overview on attacks on conventional HSMs that the IHSM is defended against. %FIXME \paragraph{...} -\subsection{Contactless probing of the payload} - -Irrespective of the HSM's technology (conventional or IHSM), there are some types of attack bypassing the HSM's security -mesh that in principle cannot be prevented. One such type are contactless attacks such as electromagnetic (EM) -sidechannel attacks, but attacks through the HSM's application interface such as Ethernet also follow this theme. While -IHSMs allow for the use of off-the-shelf server hardware as their payload, the combination of payload hardware and the -software running on top of this hardware still has to be evaluated for fitness in this particular application. EM -sidechannel attacks can be mitigated by shielding and by designing the IHSM's payload such that critical components such -as CPUs are physically distant to the security mesh, preventing EM probes from being brought close. Conducted EMI -sidechannels that could be used for power analysis can be mitigated by placing filters on the inside of the security -mesh at the point where the power and network connections penetrate the mesh. Attacks through the network interface must -be prevented as in any other networked system by only exposing the minimum necessary amount of API surface to the -outside world, and by carefully vetting this remaining attack surface. +In principle, there are three ways to attack a conventional HSM. The hard way is to find a way to go through the +security mesh without triggering the alarm, e.g.\ by using a probe that is finer than the mesh's structure size. An +attacker willing to invest some effort can also try to uncover the mesh traces buried in plastic to then hot-wire the +mesh, bridging over a part that will subsequently be removed. HSMs attempt to detect such attacks by measuring the mesh +traces' resistance instead of only checking their continuity~\cite{obermaier2019}. However, if an attacker only wishes +to disable a small section of the mesh to insert a handful of fine probes into the device, this hardening approach +becomes challenging. Consider a mesh is covering an area of $\SI{100}{\milli\meter}$ by $\SI{100}{\milli\meter}$. An +attacker who circumvents a $\SI{5}{\milli\meter}$ by $\SI{5}{\milli\meter}$ section of this mesh using wires with a low +resistance will change the mesh trace's resistance by approximately +$\frac{\SI{5}{\milli\meter}\cdot\SI{5}{\milli\meter}}{\SI{100}{\milli\meter}\cdot\SI{100}{\milli\meter}} = 0.25 +\%$. Detecting this change would require a resistance measurement of at least $\SI{9}{bit}$ of precision and +corresponding temperature stability of the mesh material. + +The second way to attack a HSM is to go \emph{around} the mesh. Many commercial HSMs sandwich the payload PCB between +two mesh-equipped enclosure halves. This design in particular is vulnerable to attempts to stick a fine needle through +the interface between mesh lid and PCB. Conventional HSMs mitigate this weak spot by wrapping a patterned conductive +foil that forms the security mesh around the HSM, leaving only the foil's corners and the payload's power and data +feed-through as potential weak spots. + +The third and last way to attack a conventional HSM is to disable the mesh monitoring circuit~\cite{dexter2015}. An +attacker may need to insert several probes to wiretap the payload processor's secrets, but depending on its +implementation they may be able to disable the mesh alarm circuit with only one. To harden a conventional HSM against +this type of attack, the mesh monitoring circuit must be carefully designed to avoid single points of failure as well as +any fail-open failure modes. + +\subsection{Attacks that work on any HSM} + +While an IHSM provides an effective mitigation against direct attacks on the security mesh as described in the previous +paragraphs, certain attacks are generic against any HSM technology, conventional or IHSM. One type of such attacks are +contactless attacks such as electromagnetic (EM) sidechannel attacks. EM sidechannel attacks can be mitigated by +shielding and by designing the IHSM's payload such that critical components such as CPUs are physically distant to the +security mesh, preventing EM probes from being brought close. Conducted EMI sidechannels that could be used for power +analysis can be mitigated by placing filters on the inside of the security mesh at the point where the power and network +connections penetrate the +mesh~\cite{anderson2020}. +Finally, the API between the HSM's payload and the outside world provides attack surface. Attacks through the network +interface must be prevented as in any other networked system by only exposing the minimum necessary amount of API +surface to the outside world, and by carefully vetting this remaining attack surface~\cite{anderson2020}. \subsection{The Swivel Chair Attack} \label{sec_swivel_chair_attack} @@ -520,6 +545,41 @@ acceleration is $a=\omega^2 r$. In our example this results in a minimum angular $\SI{1000}{rpm}$ and above, a manual attack is no longer possible and any attack would have to be carried out using some kind of mechanical tool. +\begin{figure} + \center + \includegraphics[width=6cm]{attack-robot.pdf} + \caption{Schematic overview of a robotic rotating-stage attack. An optical sensor (1) observes the IHSM's rotation + and adjusts the setpoint of a servo motor (2) that rotates the attack stage (3). On the rotating attack stage, a + remote controlled manipulator (4) is mounted that deactivates the security mesh (7) and creates an opening (5). + Through this opening, a human operator can then insert tools such as probes to read out sensitive information from + the actual payload (6).} + \label{fig_attack_robot} +\end{figure} + + +While it is certainly possible to create a mechanical tool to attack an IHSM in motion, we also consider this attack +method reasonably remote. Figure~\ref{fig_attack_robot} shows a schematic overview of what such an attack tool would +have to look like. Most fundamentally, the tool itself has to rotate at the IHSM's speed, and cannot simply rotate the +IHSM. If the tool were to counter-rotate the IHSM such that relative to a stationary observer the rotor would be slowed +down, the accelerometer on the rotor would measure lower centrifugal acceleration and detect this attempt. Instead, the +attack tool has to follow the rotation of the IHSM. At the high speeds an IHSM would be rotating at, following the +rotation closely enough that a manipulator mounted on the attack tool is stationary w.r.t.\ the IHSM is not easy. To +stay within $\pm\SI{5}{\milli\meter}$ of a target over a period of $\SI{10}{\second}$ on an IHSM mesh with radius +$r=\SI{100}{\milli\meter}$ requires both speeds to be matched to better than +$\frac{\SI{5}{\milli\meter}}{\SI{10}{\second}} \cdot \frac{1}{2\pi r} = \SI{8.0}{\milli\hertz} = \SI{0.048}{rpm}$. +Relative to a realsistic IHSM's speed of $\SI{1000}{rpm}$ this corresponds to approximately $\SI{50}{ppm}$. Active servo +control of the attack tool's rotation locked against optical tracking of the IHSM's rotor would likely be the most +realistic option to achieve this precision. This strict accuracy requirement leads to a complex attack setup. + +If an attacker were to solve the tracking issue, the remaining issue is that they still need to construct a +remote-controlled manipulator that can be mounted on the attack tool's rotating stage and that is able to actually +disable the IHSM's mesh. Consider that simply bypassing the mesh e.g. by drilling an undetected hole does not gain an +attacker much in this scenario, as the payload is stationary and an attack tool rotating at $\SI{1000}{rpm}$ is useless +against it. Instead, the attacker would have to disable the mesh using the rotating tool, in order to then cut an +opening into it through which they could insert a stationary tool to attack the payload with. Given the degree of manual +skill necessary even for normal soldering work, we estimate that creating a remote-controllable manipulator that can be +used to successfully attack a security mesh is infeasible. + \subsection{Mechanical weak spots} The tamper defense of an IHSM rests on the security mesh moving too fast to tamper. Depending on the type of motion @@ -864,12 +924,16 @@ allow the construction of devices secure against a wide range of practical attac specialized tools. The rotating mesh allows longitudinal gaps, which enables new applications that are impossible with traditional HSMs. Such gaps can be used to integrate a fan for air cooling into the HSM, allowing the use of powerful computing hardware inside the HSM. We hope that this simple construction will stimulate academic research into (more) -secure hardware. +secure hardware. We have published all design artifacts of our PoC online, see Appendix~\ref{sec_repo}. The next steps +towards a practical application of our design will be to design a manufacturable stator/rotor interface with inductive +power and data transfer integrated into the motor's magnetics and a custom motor driver tuned for the application that +is able to precisely measure both angular velocity and winding current for an added degree of tamper detection. \printbibliography[heading=bibintoc] \appendix -\section{Source code and Design artifacts} +\section{Source code and design artifacts} +\label{sec_repo} During our research on this paper, we have created a number of digital design artifacts including a 3D mechanical CAD model of our prototype IHSM, schematics and PCB layouts for all of its PCBs including the prototype security mesh |
