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+<h1>Scoring</h1>
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+
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+<p>
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+ Currently, CryptCheck gives note from <%= rank_label :G %> for the
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+ worst sites to <%= rank_label :'A+' %> for the best ones.
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+</p>
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+
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+<p>
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+ Scoring is based on the fact that TLS handshake is <b>not</b> authenticated,
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+ and so an attacker can force to use whatever cipher he wants as soon as both
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+ client and server support it, with a downgrade attack as simple as modify
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+ TCP packets on the fly.
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+</p>
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+
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+<p>
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+ Such downgrade attack doesn't require heavy resources and can be made with
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+ standard computer or phone.<br/>
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+ The only difficult part is to be in position to modify the traffic between
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+ the client and the server.
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+ This is the case if the attacker is connected on the same network as the
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+ client (hotspot, 3G…) with simple
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+ <a href="https://en.wikipedia.org/wiki/ARP_spoofing">ARP spoofing</a>,
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+ doable with tools like
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+ <a href="https://forum.xda-developers.com/showthread.php?t=1593990">Droid Sheep</a>.<br/>
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+</p>
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+
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+<p>
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+ As client support can't be guessed, CryptCheck considers the <b>weakest</b>
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+ suite supported server side.
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+ This way, a connection to the scored service can't lead to a negociated
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+ handshake with a worse score than the one given to the service, whatever
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+ your client supports and whatever an attacker is present or not.
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+</p>
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+
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+<table class="scoring table table-bordered table-condensed center table-striped">
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+ <thead>
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+ <tr>
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+ <th rowspan="2">Score</th>
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+ <td rowspan="2"></td>
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+ <td colspan="3">Protection</td>
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+ <td colspan="3">Weakness</td>
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+ </tr>
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+ <tr>
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+ <td>Best</td>
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+ <td>Great</td>
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+ <td>Good</td>
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+
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+ <td>Future</td>
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+ <td>Weak</td>
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+ <td>Deprecated</td>
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+ </tr>
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+ </thead>
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+ <tbody>
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+ <tr>
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+ <th><%= rank_label :'A+' %></th>
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+ <td class="left">
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+ Seriously take security into account and invest a lot on it.<br/>
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+ Whatever the cost, encryption safety is implemented.
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+ You can be proud!
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+ </td>
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+ <td><%= image_tag 'check-full.svg' %></td>
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+ <td><%= image_tag 'check-full.svg' %></td>
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+ <td><%= image_tag 'check-full.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ </tr>
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+ <tr>
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+ <th><%= rank_label :A %></th>
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+ <td class="left">
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+ Seriously take security into account and invest a lot on it.
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+ </td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ <td><%= image_tag 'check-full.svg' %></td>
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+ <td><%= image_tag 'check-full.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ </tr>
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+ <tr>
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+ <th><%= rank_label :'B+' %></th>
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+ <td class="left">
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+ Seriously take security into account and invest on it.
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+ </td>
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+ <td></td>
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+ <td><%= image_tag 'check-full.svg' %></td>
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+ <td><%= image_tag 'check-full.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ </tr>
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+ <tr>
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+ <th><%= rank_label :B %></th>
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+ <td class="left">
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+ Take security into account and invest on it.
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+ </td>
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+ <td></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ <td><%= image_tag 'check-full.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ </tr>
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+ <tr>
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+ <th><%= rank_label :'C+' %></th>
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+ <td class="left">
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+ Take security into account and invest a little on it.
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+ </td>
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+ <td></td>
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+ <td></td>
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+ <td><%= image_tag 'check-full.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ </tr>
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+ <tr>
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+ <th><%= rank_label :C %></th>
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+ <td class="left">
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+ Take security into account but don't spend too much for it.
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+ </td>
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+ <td></td>
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+ <td></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ </tr>
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+ <tr>
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+ <th><%= rank_label :D %></th>
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+ <td class="left">
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+ Take security into account. Minimaly.<br/>
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+ This is the worst score a decent service must have today.
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+ </td>
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+ <td></td>
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+ <td></td>
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+ <td></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ </tr>
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+ <tr>
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+ <th><%= rank_label :E %></th>
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+ <td class="left">
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+ Take security into account. A little. Or not.
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+ </td>
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+ <td></td>
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+ <td></td>
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+ <td></td>
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+ <td><%= image_tag 'cross-red.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ </tr>
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+ <tr>
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+ <th><%= rank_label :F %></th>
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+ <td class="left">
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+ Just don't take security into account.
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+ </td>
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+ <td></td>
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+ <td></td>
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+ <td></td>
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+ <td></td>
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+ <td><%= image_tag 'cross-red.svg' %></td>
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+ <td><%= image_tag 'check-empty.svg' %></td>
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+ </tr>
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+ <tr>
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+ <th><%= rank_label :G %></th>
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+ <td class="left">
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+ Just don't take security into account at all.<br/>
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+ What the fuck you do, dude?
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+ </td>
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+ <td></td>
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+ <td></td>
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+ <td></td>
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+ <td></td>
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+ <td></td>
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+ <td><%= image_tag 'cross-red.svg' %></td>
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+ </tr>
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+ <tr>
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+ <th><%= rank_label :'0' %></th>
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+ <td class="left">
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+ No security at all. Just plain text.<br/>
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+ Seriously, in <%= Date.today.year %>?
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+ </td>
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+ <td colspan="6"></td>
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+ </tr>
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+ <tr>
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+ <th><%= rank_label :V %></th>
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+ <td class="left">
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+ Invalid certificate (wrong domain, expired…)
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+ </td>
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+ <td colspan="6"></td>
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+ </tr>
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+ <tr>
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+ <th><%= rank_label :T %></th>
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+ <td class="left">
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+ Unstrusted certificate. Not issued by a trusted
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+ <a href="https://ccadb-public.secure.force.com/mozilla/IncludedCACertificateReport">certificate authority</a>.
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+ </td>
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+ <td colspan="6"></td>
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+ </tr>
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+ <tr>
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+ <th><%= rank_label :X %></th>
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+ <td class="left">
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+ Error occurs during the analysis. Try again later?
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+ </td>
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+ <td colspan="6"></td>
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+ </tr>
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+ </tbody>
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+</table>
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+<table class="scoring table table-bordered table-condensed">
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+ <tr>
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+ <td>
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+ For protection:<br/>
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+ <%= image_tag 'check-full.svg' %> Fully implemented
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+ <%= image_tag 'check-empty.svg' %> Partially implemented<br/>
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+
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+ Good: simple to implement, small protection<br/>
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+ Great: quiet hard to implement, middle protection<br/>
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+ Best: hard to implement, strong protection
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+ </td>
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+ <td>
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+ For weakness:<br/>
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+ <%= image_tag 'check-empty.svg' %> Not vulnerable
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+ <%= image_tag 'cross-red.svg' %> Vulnerable<br/>
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+
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+ Future: known weakness, but no practical attack known<br/>
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+ Weak: known weakness, pratical attack exist<br/>
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+ Deprecated: known weakness, merely equivalent or equal to plain text
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+ </td>
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+ </tr>
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+</table>
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+
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+<p>
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+ <i>Note</i>: Unlike HTTPS or XMPP, SMTP uses
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+ <a href="https://en.wikipedia.org/wiki/Opportunistic_TLS">opportunistic encryption</a>.<br/>
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+ When you send an email, the server used to forward the mail (the
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+ <a href="https://en.wikipedia.org/wiki/Message_transfer_agent">MTA</a>) to
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+ the recipient has no way to guess in advance if recipient MTA supports or
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+ not encryption and which cipher suite will be available.
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+ To avoid your email returning to you in case of failure, the standard for
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+ email encryption (<a href="https://tools.ietf.org/html/rfc3207">RFC 3207</a>)
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+ requires to retry <b>in plain text</b> in case of encryption handshake
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+ failure.<br/>
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+ So, for SMTP, there is a compromise to make between strong configuration,
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+ leading to plain text fallback for old or badly configured MTA, and
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+ compatibility with such MTA to use weak encryption better than plain text
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+ but allowing downgrade attack on stronger MTA.<br/>
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+ Given email is a real nightmare for security, with multiple way to force a
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+ connection to fallback to plain text
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+ (<a href="https://www.eff.org/fr/deeplinks/2014/11/starttls-downgrade-attacks">STARTTLS stripping</a>,
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+ <a href="https://labs.ripe.net/Members/stephane_bortzmeyer/dns-censorship-dns-lies-seen-by-atlas-probes">MX lying</a>…),
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+ CryptCheck scores SMTP as HTTPS or XMPP and doesn't care about compatibility
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+ trouble. This way, weak people are still weak, but strong people can (not
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+ too much) hope strong encryption under normal condition.<br/>
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+ Be advice than strong score here for SMTP means compatibility troubles.
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+ Or fucked service which doesn't take care of your security.
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+ I don't know, you turn to judge.
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+</p>
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