<div dir="ltr"><br clear="all"><div>Hi,</div><div><br></div><div><table style="margin:0px;padding:0px;border:0px;font-size:13px;border-collapse:collapse;color:rgb(36,39,41);font-family:"open sans","helvetica neue",helvetica,arial,sans-serif"><tbody style="margin:0px;padding:0px;border:0px"><tr style="margin:0px;padding:0px;border:0px"><td class="gmail-postcell" style="padding:0px;border:0px;vertical-align:top"><div style="margin:0px;padding:0px;border:0px"></div></td><td class="gmail-votecell" style="padding:0px 15px 0px 0px;border:0px;vertical-align:top"><div class="gmail-vote" style="margin:0px;padding:0px;border:0px;text-align:center;min-width:46px"><span class="gmail-vote-count-post" style="margin:8px 0px;padding:0px;border:0px;font-size:20px;display:block;color:rgb(106,115,124)"><br class="gmail-Apple-interchange-newline"><br></span><a class="gmail-vote-down-off" title="This question does not show any research effort; it is unclear or not useful" style="margin:0px auto 10px;padding:0px;border:0px;font-size:1px;color:rgb(41,128,255);background-image:url("");background-size:initial;background-repeat:no-repeat;overflow:hidden;display:block;width:40px;height:40px;background-position:0px -220px">down vote</a><a class="gmail-star-off" href="http://crypto.stackexchange.com/questions/43612/why-do-we-try-out-all-possible-combinations-of-top-bits-in-openssl-timing-attack#" title="Click to mark as favorite question (click again to undo)" style="margin:0px auto 2px;padding:0px;border:0px;font-size:1px;color:rgb(41,128,255);text-decoration:none;background-image:url("");background-size:initial;background-repeat:no-repeat;overflow:hidden;display:block;width:40px;height:30px;background-position:0px -120px">favorite</a><div class="gmail-favoritecount" style="margin:0px;padding:0px;border:0px"><span style="margin:0px;padding:0px;border:0px;color:rgb(106,115,124)"></span></div></div></td><td class="gmail-postcell" style="padding:0px;border:0px;vertical-align:top"><div style="margin:0px;padding:0px;border:0px"><div class="gmail-post-text" style="margin:0px 0px 5px;padding:0px;border:0px;font-size:15px;width:660px;word-wrap:break-word;line-height:1.3"><p style="margin:0px 0px 1em;padding:0px;border:0px;clear:both">In the paper titled <a href="https://crypto.stanford.edu/~dabo/papers/ssl-timing.pdf" rel="nofollow noreferrer" style="margin:0px;padding:0px;border:0px;color:rgb(41,128,255);text-decoration:none">Remote Timing Attacks are Practical</a>, the authors mention the following:</p><blockquote style="margin:0px 0px 10px;padding:10px;border-width:0px 0px 0px 2px;border-top-style:initial;border-right-style:initial;border-bottom-style:initial;border-left-style:solid;border-top-color:initial;border-right-color:initial;border-bottom-color:initial;border-left-color:rgb(255,235,142);quotes:none;background-color:rgb(255,249,227)"><p style="margin:0px;padding:0px;border:0px;clear:both">Initially our guess <code style="margin:0px;padding:1px 5px;border:0px;font-size:13px;font-family:consolas,menlo,monaco,"lucida console","liberation mono","dejavu sans mono","bitstream vera sans mono","courier new",monospace,sans-serif;background-color:rgb(239,240,241);white-space:pre-wrap">g</code> of <code style="margin:0px;padding:1px 5px;border:0px;font-size:13px;font-family:consolas,menlo,monaco,"lucida console","liberation mono","dejavu sans mono","bitstream vera sans mono","courier new",monospace,sans-serif;background-color:rgb(239,240,241);white-space:pre-wrap">q</code> lies between <span class="gmail-MathJax" id="gmail-MathJax-Element-1-Frame" tabindex="0" style="margin:0px;padding:0px;border:0px;display:inline;line-height:normal;word-spacing:normal;word-wrap:normal;white-space:nowrap;float:none;direction:ltr;max-width:none;max-height:none;min-width:0px;min-height:0px"><span style="border:0px;padding:0px;margin:0px;max-width:none;max-height:none;min-width:0px;min-height:0px;vertical-align:0px;line-height:normal"><span class="gmail-math" id="gmail-MathJax-Span-1" style="margin:0px;padding:0px;border:0px;display:inline-block;vertical-align:0px;line-height:normal;width:2.046em"><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:1.616em;height:0px"><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;vertical-align:0px;line-height:normal"><span class="gmail-mrow" id="gmail-MathJax-Span-2" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal"><span class="gmail-msubsup" id="gmail-MathJax-Span-3" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal"><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:1.616em;height:0px"><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;vertical-align:0px;line-height:normal"><span class="gmail-mn" id="gmail-MathJax-Span-4" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral">2</span><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:0px;height:3.981em"></span></span><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;vertical-align:0px;line-height:normal"><span class="gmail-texatom" id="gmail-MathJax-Span-5" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal"><span class="gmail-mrow" id="gmail-MathJax-Span-6" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal"><span class="gmail-mn" id="gmail-MathJax-Span-7" style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral">512</span></span></span><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:0px;height:3.981em"></span></span></span></span></span><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:0px;height:2.315em"></span></span></span><span style="margin:0px;padding:0px;border-width:0px;border-top-style:initial;border-right-style:initial;border-bottom-style:initial;border-left-style:solid;border-color:initial;display:inline-block;vertical-align:-0.063em;line-height:normal;overflow:hidden;width:0px;height:1.27em"></span></span></span><span class="gmail-MJX_Assistive_MathML" style="margin:0px;padding:0px;border:0px;display:inline;vertical-align:0px;line-height:normal;height:1px;width:1px;overflow:hidden"><span><span><span>2</span><span class="gmail-MJX-TeXAtom-ORD"><span>512</span></span></span></span></span></span> (i.e. <span class="gmail-MathJax" id="gmail-MathJax-Element-2-Frame" tabindex="0" style="margin:0px;padding:0px;border:0px;display:inline;line-height:normal;word-spacing:normal;word-wrap:normal;white-space:nowrap;float:none;direction:ltr;max-width:none;max-height:none;min-width:0px;min-height:0px"><span style="border:0px;padding:0px;margin:0px;max-width:none;max-height:none;min-width:0px;min-height:0px;vertical-align:0px;line-height:normal"><span class="gmail-math" id="gmail-MathJax-Span-8" style="margin:0px;padding:0px;border:0px;display:inline-block;vertical-align:0px;line-height:normal;width:4.142em"><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:3.336em;height:0px"><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;vertical-align:0px;line-height:normal"><span class="gmail-mrow" id="gmail-MathJax-Span-9" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal"><span class="gmail-msubsup" id="gmail-MathJax-Span-10" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal"><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:3.336em;height:0px"><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;vertical-align:0px;line-height:normal"><span class="gmail-mn" id="gmail-MathJax-Span-11" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral">2</span><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:0px;height:3.981em"></span></span><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;vertical-align:0px;line-height:normal"><span class="gmail-texatom" id="gmail-MathJax-Span-12" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal"><span class="gmail-mrow" id="gmail-MathJax-Span-13" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal"><span class="gmail-mi" id="gmail-MathJax-Span-14" style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral;font-style:italic">l<span style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline-block;vertical-align:0px;line-height:normal;overflow:hidden;height:1px;width:0.003em"></span></span><span class="gmail-mi" id="gmail-MathJax-Span-15" style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral;font-style:italic">o</span><span class="gmail-msubsup" id="gmail-MathJax-Span-16" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal"><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:0.648em;height:0px"><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;vertical-align:0px;line-height:normal"><span class="gmail-mi" id="gmail-MathJax-Span-17" style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral;font-style:italic">g</span><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:0px;height:3.981em"></span></span><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;vertical-align:0px;line-height:normal"><span class="gmail-mn" id="gmail-MathJax-Span-18" style="margin:0px;padding:0px;border:0px;font-size:9.3px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral">2</span><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:0px;height:3.981em"></span></span></span></span><span class="gmail-mo" id="gmail-MathJax-Span-19" style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral">(</span><span class="gmail-mi" id="gmail-MathJax-Span-20" style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral;font-style:italic">N<span style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline-block;vertical-align:0px;line-height:normal;overflow:hidden;height:1px;width:0.056em"></span></span><span class="gmail-texatom" id="gmail-MathJax-Span-21" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal"><span class="gmail-mrow" id="gmail-MathJax-Span-22" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal"><span class="gmail-mo" id="gmail-MathJax-Span-23" style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral">/</span></span></span><span class="gmail-mn" id="gmail-MathJax-Span-24" style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral">2</span><span class="gmail-mo" id="gmail-MathJax-Span-25" style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral">)</span></span></span><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:0px;height:3.981em"></span></span></span></span></span><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:0px;height:2.315em"></span></span></span><span style="margin:0px;padding:0px;border-width:0px;border-top-style:initial;border-right-style:initial;border-bottom-style:initial;border-left-style:solid;border-color:initial;display:inline-block;vertical-align:-0.063em;line-height:normal;overflow:hidden;width:0px;height:1.203em"></span></span></span><span class="gmail-MJX_Assistive_MathML" style="margin:0px;padding:0px;border:0px;display:inline;vertical-align:0px;line-height:normal;height:1px;width:1px;overflow:hidden"><span><span><span>2</span><span class="gmail-MJX-TeXAtom-ORD"><span>l</span><span>o</span><span><span>g</span><span>2</span></span><span>(</span><span>N</span><span class="gmail-MJX-TeXAtom-ORD"><span>/</span></span><span>2</span><span>)</span></span></span></span></span></span>) and <span class="gmail-MathJax" id="gmail-MathJax-Element-3-Frame" tabindex="0" style="margin:0px;padding:0px;border:0px;display:inline;line-height:normal;word-spacing:normal;word-wrap:normal;white-space:nowrap;float:none;direction:ltr;max-width:none;max-height:none;min-width:0px;min-height:0px"><span style="border:0px;padding:0px;margin:0px;max-width:none;max-height:none;min-width:0px;min-height:0px;vertical-align:0px;line-height:normal"><span class="gmail-math" id="gmail-MathJax-Span-26" style="margin:0px;padding:0px;border:0px;display:inline-block;vertical-align:0px;line-height:normal;width:2.046em"><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:1.616em;height:0px"><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;vertical-align:0px;line-height:normal"><span class="gmail-mrow" id="gmail-MathJax-Span-27" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal"><span class="gmail-msubsup" id="gmail-MathJax-Span-28" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal"><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:1.616em;height:0px"><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;vertical-align:0px;line-height:normal"><span class="gmail-mn" id="gmail-MathJax-Span-29" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral">2</span><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:0px;height:3.981em"></span></span><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;vertical-align:0px;line-height:normal"><span class="gmail-texatom" id="gmail-MathJax-Span-30" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal"><span class="gmail-mrow" id="gmail-MathJax-Span-31" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal"><span class="gmail-mn" id="gmail-MathJax-Span-32" style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral">511</span></span></span><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:0px;height:3.981em"></span></span></span></span></span><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:0px;height:2.315em"></span></span></span><span style="margin:0px;padding:0px;border-width:0px;border-top-style:initial;border-right-style:initial;border-bottom-style:initial;border-left-style:solid;border-color:initial;display:inline-block;vertical-align:-0.063em;line-height:normal;overflow:hidden;width:0px;height:1.27em"></span></span></span><span class="gmail-MJX_Assistive_MathML" style="margin:0px;padding:0px;border:0px;display:inline;vertical-align:0px;line-height:normal;height:1px;width:1px;overflow:hidden"><span><span><span>2</span><span class="gmail-MJX-TeXAtom-ORD"><span>511</span></span></span></span></span></span> (i.e. <span class="gmail-MathJax" id="gmail-MathJax-Element-4-Frame" tabindex="0" style="margin:0px;padding:0px;border:0px;display:inline;line-height:normal;word-spacing:normal;word-wrap:normal;white-space:nowrap;float:none;direction:ltr;max-width:none;max-height:none;min-width:0px;min-height:0px"><span style="border:0px;padding:0px;margin:0px;max-width:none;max-height:none;min-width:0px;min-height:0px;vertical-align:0px;line-height:normal"><span class="gmail-math" id="gmail-MathJax-Span-33" style="margin:0px;padding:0px;border:0px;display:inline-block;vertical-align:0px;line-height:normal;width:5.164em"><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:4.142em;height:0px"><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;vertical-align:0px;line-height:normal"><span class="gmail-mrow" id="gmail-MathJax-Span-34" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal"><span class="gmail-msubsup" id="gmail-MathJax-Span-35" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal"><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:4.142em;height:0px"><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;vertical-align:0px;line-height:normal"><span class="gmail-mn" id="gmail-MathJax-Span-36" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral">2</span><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:0px;height:3.981em"></span></span><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;vertical-align:0px;line-height:normal"><span class="gmail-texatom" id="gmail-MathJax-Span-37" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal"><span class="gmail-mrow" id="gmail-MathJax-Span-38" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal"><span class="gmail-mi" id="gmail-MathJax-Span-39" style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral;font-style:italic">l<span style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline-block;vertical-align:0px;line-height:normal;overflow:hidden;height:1px;width:0.003em"></span></span><span class="gmail-mi" id="gmail-MathJax-Span-40" style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral;font-style:italic">o</span><span class="gmail-msubsup" id="gmail-MathJax-Span-41" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal"><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:0.648em;height:0px"><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;vertical-align:0px;line-height:normal"><span class="gmail-mi" id="gmail-MathJax-Span-42" style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral;font-style:italic">g</span><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:0px;height:3.981em"></span></span><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;vertical-align:0px;line-height:normal"><span class="gmail-mn" id="gmail-MathJax-Span-43" style="margin:0px;padding:0px;border:0px;font-size:9.3px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral">2</span><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:0px;height:3.981em"></span></span></span></span><span class="gmail-mo" id="gmail-MathJax-Span-44" style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral">(</span><span class="gmail-mi" id="gmail-MathJax-Span-45" style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral;font-style:italic">N<span style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline-block;vertical-align:0px;line-height:normal;overflow:hidden;height:1px;width:0.056em"></span></span><span class="gmail-texatom" id="gmail-MathJax-Span-46" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal"><span class="gmail-mrow" id="gmail-MathJax-Span-47" style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline;vertical-align:0px;line-height:normal"><span class="gmail-mo" id="gmail-MathJax-Span-48" style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral">/</span></span></span><span class="gmail-mn" id="gmail-MathJax-Span-49" style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral">2</span><span class="gmail-mo" id="gmail-MathJax-Span-50" style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral">)</span><span class="gmail-mo" id="gmail-MathJax-Span-51" style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral">−</span><span class="gmail-mn" id="gmail-MathJax-Span-52" style="margin:0px;padding:0px;border:0px;font-size:13.1502px;display:inline;vertical-align:0px;line-height:normal;font-family:stixgeneral">1</span></span></span><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:0px;height:3.981em"></span></span></span></span></span><span style="margin:0px;padding:0px;border:0px;font-size:18.6px;display:inline-block;vertical-align:0px;line-height:normal;width:0px;height:2.315em"></span></span></span><span style="margin:0px;padding:0px;border-width:0px;border-top-style:initial;border-right-style:initial;border-bottom-style:initial;border-left-style:solid;border-color:initial;display:inline-block;vertical-align:-0.063em;line-height:normal;overflow:hidden;width:0px;height:1.203em"></span></span></span><span class="gmail-MJX_Assistive_MathML" style="margin:0px;padding:0px;border:0px;display:inline;vertical-align:0px;line-height:normal;height:1px;width:1px;overflow:hidden"><span><span><span>2</span><span class="gmail-MJX-TeXAtom-ORD"><span>l</span><span>o</span><span><span>g</span><span>2</span></span><span>(</span><span>N</span><span class="gmail-MJX-TeXAtom-ORD"><span>/</span></span><span>2</span><span>)</span><span>−</span><span>1</span></span></span></span></span></span>). We then time the decryption of all possible combinations of the top few bits (typically 2-3). When plotted, the decryption times will show two peaks: one for <code style="margin:0px;padding:1px 5px;border:0px;font-size:13px;font-family:consolas,menlo,monaco,"lucida console","liberation mono","dejavu sans mono","bitstream vera sans mono","courier new",monospace,sans-serif;background-color:rgb(239,240,241);white-space:pre-wrap">q</code> and one for <code style="margin:0px;padding:1px 5px;border:0px;font-size:13px;font-family:consolas,menlo,monaco,"lucida console","liberation mono","dejavu sans mono","bitstream vera sans mono","courier new",monospace,sans-serif;background-color:rgb(239,240,241);white-space:pre-wrap">p</code>. We pick the values that bound the first peak, which in OpenSSL will always be <code style="margin:0px;padding:1px 5px;border:0px;font-size:13px;font-family:consolas,menlo,monaco,"lucida console","liberation mono","dejavu sans mono","bitstream vera sans mono","courier new",monospace,sans-serif;background-color:rgb(239,240,241);white-space:pre-wrap">q</code>.</p></blockquote><p style="margin:0px 0px 1em;padding:0px;border:0px;clear:both">I don't understand the following:</p><ul style="margin:0px 0px 1em 30px;padding:0px;border:0px"><li style="margin:0px 0px 0.5em;padding:0px;border:0px;word-wrap:break-word">Does the initial guess of <code style="margin:0px;padding:1px 5px;border:0px;font-size:13px;font-family:consolas,menlo,monaco,"lucida console","liberation mono","dejavu sans mono","bitstream vera sans mono","courier new",monospace,sans-serif;background-color:rgb(239,240,241);white-space:pre-wrap">g</code> start from an arbitrary range?</li><li style="margin:0px 0px 0.5em;padding:0px;border:0px;word-wrap:break-word">What's the rationale behind trying out top 2-3 bits?</li><li style="margin:0px 0px 0.5em;padding:0px;border:0px;word-wrap:break-word">What will the remaining bits be in this case?</li></ul></div></div></td></tr></tbody></table><br></div>-- <br><div class="gmail_signature"><div dir="ltr"><span><div><div dir="ltr"><p>Thanks & Regards,</p>
<div>Dipanjan</div></div></div></span></div></div>
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