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<h1 id="tutorial-setting-up-derivepassphrase-vault-for-three-accounts-with-a-master-passphrase">Tutorial: setting up <code>derivepassphrase vault</code> for three accounts, with a master passphrase<a class="headerlink" href="#tutorial-setting-up-derivepassphrase-vault-for-three-accounts-with-a-master-passphrase" title="Permanent link">&para;</a></h1>
<h2 id="the-scenario">The scenario<a class="headerlink" href="#the-scenario" title="Permanent link">&para;</a></h2>
<p>In this tutorial, we will setup <code>derivepassphrase</code> for three services, using a master passphrase and the standard <code>vault</code> passphrase derivation scheme.
We will assume the following three services with the following passphrase policies:</p>
<div class="grid cards">
<ul>
<li>
<p><strong>email account</strong></p>
<hr />
<ul>
<li>between 12 and 20 characters</li>
<li>no spaces</li>
<li>1 upper case letter, 1 lower case letter, 1 digit</li>
<li>no character immediately repeated more than 3 times</li>
</ul>
</li>
<li>
<p><strong>bank account</strong></p>
<hr />
<ul>
<li>only digits</li>
<li>exactly 5 digits</li>
<li>an additional one-time password via a hardware token (&ldquo;<a href="https://en.wikipedia.org/wiki/Two-factor_authentication">two-factor authentication</a>&rdquo;)</li>
</ul>
</li>
<li>
<p><strong>work account</strong></p>
<hr />
<ul>
<li>exactly 8 characters</li>
<li>no spaces</li>
<li>1 special character, 1 letter, 1 digit</li>
<li>must be changed every quarter (January, April, July and October) to a different value (&ldquo;passphrase rotation&rdquo; or &ldquo;rollover&rdquo;)</li>
<li>must actually be different from the previous <em>two</em> passphrases</li>
</ul>
</li>
</ul>
</div>
<h2 id="installing-derivepassphrase">Installing <code>derivepassphrase</code><a class="headerlink" href="#installing-derivepassphrase" title="Permanent link">&para;</a></h2>
<p>Install <code>pipx</code>:</p>
<div class="highlight"><pre><span></span><code><span class="gp">$ </span><span class="nb">cd</span><span class="w"> </span>~
<span class="gp">$ </span>python3<span class="w"> </span>-m<span class="w"> </span>venv<span class="w"> </span>.venv
<span class="gp">$ </span>.<span class="w"> </span>.venv/bin/activate
<span class="gp">$ </span>pip<span class="w"> </span>install<span class="w"> </span>pipx
</code></pre></div>
<p>Install <code>derivepassphrase</code>:</p>
<div class="highlight"><pre><span></span><code><span class="gp">$ </span>pipx<span class="w"> </span>install<span class="w"> </span>derivepassphrase
</code></pre></div>
<p>Check that the installation was successful.</p>
<div class="highlight"><pre><span></span><code><span class="gp">$ </span>devirepassphrase<span class="w"> </span>--version
<span class="go">derivepassphrase, version 0.2.0</span>
</code></pre></div>
<p>(…or similar output.)</p>
<h2 id="choosing-a-master-passphrase">Choosing a master passphrase<a class="headerlink" href="#choosing-a-master-passphrase" title="Permanent link">&para;</a></h2>
<p><code>derivepassphrase</code> uses a master passphrase <code>MP</code>, and derives all other passphrases <code>P</code> from <code>MP</code>.
We shall choose the master passphrase: <code>I am an insecure master passphrase, but easy to type.</code></p>
<h2 id="setting-up-the-email-account">Setting up the email account<a class="headerlink" href="#setting-up-the-email-account" title="Permanent link">&para;</a></h2>
<p>In <code>derivepassphrase</code>, each passphrase configuration contains a <em>service name</em>, which is how <code>derivepassphrase</code> distinguishes between configurations.
This service name can be chosen freely, but the resulting passphrase depends on the chosen service name.
For our email account, we choose the straightforward service name <code>email</code>.</p>
<p>We need to translate the passphrase policy into options for <code>derivepassphrase</code>:</p>
<ul>
<li>A policy &ldquo;(at least) <code>n</code> upper case letters&rdquo; translates to the option <code>--lower n</code>, for any <code>n</code> greater than 0.
  Lower case letters (<code>--upper</code>), digits (<code>--number</code>), symbols (<code>--symbol</code>), spaces (<code>--space</code>) and dashes (<code>--dash</code>) work similarly.</li>
<li>A policy &ldquo;spaces <em>forbidden</em>&rdquo; translates to the option <code>--space 0</code>.
  Again, other character classes behave similarly.</li>
<li>A policy &ldquo;no character immediately repeated more than <code>n</code> times&rdquo; translates to the option <code>--repeat n</code>, for any <code>n</code> greater than 0.
  In particular, <code>--repeat 1</code> means no character may be immediately repeated.</li>
<li>A policy &ldquo;between <code>n</code> and <code>m</code> characters long&rdquo; translates to <code>--length k</code>, for any <code>k</code> between <code>n</code> and <code>m</code> which you choose.
  (<code>derivepassphrase</code> does not explicitly choose a passphrase length for you.)</li>
</ul>
<p>For the <code>email</code> service, we choose passphrase length 12.
This leads to the command-line options <code>--length 12 --space 0 --upper 1 --lower 1 --number 1 --repeat 3</code>.
Because we are using a master passphrase, we also need the <code>-p</code> option.</p>
<div class="admonition note">
<p class="admonition-title">Note: interactive input</p>
<p>In code listings, sections enclosed in <code>[[...]]</code> signify input to the program, for you to type or paste in.</p>
<p>Also, it is normal for passphrase prompts to not &ldquo;echo&rdquo; the text you type in.</p>
</div>
<div class="highlight"><pre><span></span><code><span class="gp">$ </span>derivepassphrase<span class="w"> </span>vault<span class="w"> </span>--length<span class="w"> </span><span class="m">12</span><span class="w"> </span>--space<span class="w"> </span><span class="m">0</span><span class="w"> </span>--upper<span class="w"> </span><span class="m">1</span><span class="w"> </span>--lower<span class="w"> </span><span class="m">1</span><span class="w"> </span><span class="se">\</span>
<span class="gp">&gt; </span><span class="w">                       </span>--number<span class="w"> </span><span class="m">1</span><span class="w"> </span>--repeat<span class="w"> </span><span class="m">3</span><span class="w"> </span>-p<span class="w"> </span>email
<span class="go">Passphrase: [[I am an insecure master passphrase, but easy to type.]]</span>
<span class="go">kEFwoD=C?@+7</span>
</code></pre></div>
<p>By design, we can re-generate the same passphrase using the same input to <code>derivepassphrase</code>:</p>
<div class="highlight"><pre><span></span><code><span class="gp">$ </span>derivepassphrase<span class="w"> </span>vault<span class="w"> </span>--length<span class="w"> </span><span class="m">12</span><span class="w"> </span>--space<span class="w"> </span><span class="m">0</span><span class="w"> </span>--upper<span class="w"> </span><span class="m">1</span><span class="w"> </span>--lower<span class="w"> </span><span class="m">1</span><span class="w"> </span><span class="se">\</span>
<span class="gp">&gt; </span><span class="w">                       </span>--number<span class="w"> </span><span class="m">1</span><span class="w"> </span>--repeat<span class="w"> </span><span class="m">3</span><span class="w"> </span>-p<span class="w"> </span>email
<span class="go">Passphrase: [[I am an insecure master passphrase, but easy to type.]]</span>
<span class="go">kEFwoD=C?@+7</span>
</code></pre></div>
<p>We can then visit our email provider and change the passphrase to <code>kEFwoD=C?@+7</code>.</p>
<h3 id="storing-the-settings-to-disk">Storing the settings to disk<a class="headerlink" href="#storing-the-settings-to-disk" title="Permanent link">&para;</a></h3>
<p>Because it is tedious to memorize and type in the correct settings to re-generate this passphrase, <code>derivepassphrase</code> can optionally store these settings, using the <code>--config</code> option.</p>
<div class="highlight"><pre><span></span><code><span class="gp">$ </span>derivepassphrase<span class="w"> </span>vault<span class="w"> </span>--config<span class="w"> </span>--length<span class="w"> </span><span class="m">12</span><span class="w"> </span>--space<span class="w"> </span><span class="m">0</span><span class="w"> </span>--upper<span class="w"> </span><span class="m">1</span><span class="w"> </span>--lower<span class="w"> </span><span class="m">1</span><span class="w"> </span><span class="se">\</span>
<span class="gp">&gt; </span><span class="w">                       </span>--number<span class="w"> </span><span class="m">1</span><span class="w"> </span>--repeat<span class="w"> </span><span class="m">3</span><span class="w"> </span>email
</code></pre></div>
<div class="admonition warning">
<p class="admonition-title">Warning: <code>-p</code> and <code>--config</code></p>
<p>Do <strong>not</strong> use the <code>-p</code> and the <code>--config</code> options together to store the master passphrase!
The configuration is assumed to <em>not contain sensitive contents</em> and is <em>not encrypted</em>, so your master passphrase is then visible to <em>anyone</em> with appropriate priviledges!</p>
</div>
<p>Check that the settings are stored correctly:</p>
<div class="highlight"><pre><span></span><code><span class="gp">$ </span>derivepassphrase<span class="w"> </span>vault<span class="w"> </span>--export<span class="w"> </span>-
<span class="go">{&quot;services&quot;: {&quot;email&quot;: {&quot;length&quot;: 12, &quot;repeat&quot;: 3, &quot;lower&quot;: 1, &quot;upper&quot;: 1, &quot;number&quot;: 1, &quot;space&quot;: 0}}}</span>
</code></pre></div>
<p>Once the settings are stored, only the service name and the master passphrase option are necessary:</p>
<div class="highlight"><pre><span></span><code><span class="gp">$ </span>derivepassphrase<span class="w"> </span>vault<span class="w"> </span>-p<span class="w"> </span>email
<span class="go">Passphrase: [[I am an insecure master passphrase, but easy to type.]]</span>
<span class="go">kEFwoD=C?@+7</span>
</code></pre></div>
<h2 id="setting-up-the-bank-account">Setting up the bank account<a class="headerlink" href="#setting-up-the-bank-account" title="Permanent link">&para;</a></h2>
<p>We choose the straightforward service name <code>bank</code>.
The passphrase policy leads to the command-line options <code>--length 5 --lower 0 --upper 0 --number 5 --space 0 --dash 0 --symbol 0</code>.</p>
<p>The additional one-time password is generated by the hardware token, and therefore out of the scope for <code>derivepassphrase</code>.</p>
<p>The rest is similar to the <code>email</code> account: we configure our stored settings, generate the passphrase, and request the bank change the account passphrase to match the generated passphrase.</p>
<div class="highlight"><pre><span></span><code><span class="gp">$ </span>derivepassphrase<span class="w"> </span>vault<span class="w"> </span>--config<span class="w"> </span>--length<span class="w"> </span><span class="m">5</span><span class="w"> </span>--lower<span class="w"> </span><span class="m">0</span><span class="w"> </span>--upper<span class="w"> </span><span class="m">0</span><span class="w"> </span>--number<span class="w"> </span><span class="m">5</span><span class="w"> </span><span class="se">\</span>
<span class="gp">&gt; </span><span class="w">                       </span>--space<span class="w"> </span><span class="m">0</span><span class="w"> </span>--dash<span class="w"> </span><span class="m">0</span><span class="w"> </span>--symbol<span class="w"> </span><span class="m">0</span><span class="w"> </span>bank
<span class="gp">$ </span>derivepassphrase<span class="w"> </span>vault<span class="w"> </span>-p<span class="w"> </span>bank
<span class="go">Passphrase: [[I am an insecure master passphrase, but easy to type.]]</span>
<span class="go">98517</span>
</code></pre></div>
<h2 id="setting-up-the-work-account">Setting up the work account<a class="headerlink" href="#setting-up-the-work-account" title="Permanent link">&para;</a></h2>
<p>We first take care of the first two constraints (passphrase length and permitted/required characters), then deal with the passphrase change/reuse aspects afterwards.
Again, we start with the straightforward service name <code>work</code>, we choose &ldquo;upper case letters&rdquo; to fulfill the &ldquo;1 letter&rdquo; requirement, and add the options <code>--length 8 --space 0 --symbol 1 --upper 1 --number 1</code>.</p>
<div class="highlight"><pre><span></span><code><span class="gp">$ </span>derivepassphrase<span class="w"> </span>vault<span class="w"> </span>--length<span class="w"> </span><span class="m">8</span><span class="w"> </span>--space<span class="w"> </span><span class="m">0</span><span class="w"> </span>--symbol<span class="w"> </span><span class="m">1</span><span class="w"> </span>--upper<span class="w"> </span><span class="m">1</span><span class="w"> </span>--number<span class="w"> </span><span class="m">1</span><span class="w"> </span><span class="se">\</span>
<span class="gp">&gt; </span><span class="w">                       </span>-p<span class="w"> </span>work
<span class="go">Passphrase: [[I am an insecure master passphrase, but easy to type.]]</span>
<span class="go">r?9\XQR&amp;</span>
</code></pre></div>
<p>Then we attempt to set the work passphrase to <code>r?9\XQR&amp;</code>… but our employer&rsquo;s identity management system returns an error: <code>illegal character: &amp;</code>.
What happened?</p>
<h3 id="complication-1-what-is-a-permitted-special-character">Complication 1: What is a (permitted) &ldquo;special character&rdquo;?<a class="headerlink" href="#complication-1-what-is-a-permitted-special-character" title="Permanent link">&para;</a></h3>
<p><code>derivepassphrase</code> considers the characters <code>!"#$%&amp;'()*+,./:;&lt;=&gt;?@[\]^{|}~-_'</code> to be permitted special characters.
Other service providers may permit other characters (quite rare) or fewer characters (quite common).
(Service providers may also <em>not</em> explicitly say which special characters they permit, except through trial and error.)</p>
<div class="admonition abstract">
<p class="admonition-title">Further reading</p>
<p>→ How to deal with &ldquo;supported&rdquo; and &ldquo;unsupported&rdquo; special characters (TODO)</p>
</div>
<p>For this case specifically, we restrict ourselves to the dashes as the only permitted special characters, and hope that this passes their passphrase policy.</p>
<div class="highlight"><pre><span></span><code><span class="gp">$ </span>derivepassphrase<span class="w"> </span>vault<span class="w"> </span>--length<span class="w"> </span><span class="m">8</span><span class="w"> </span>--space<span class="w"> </span><span class="m">0</span><span class="w"> </span>--symbol<span class="w"> </span><span class="m">0</span><span class="w"> </span>--dash<span class="w"> </span><span class="m">1</span><span class="w"> </span><span class="se">\</span>
<span class="gp">&gt; </span><span class="w">                       </span>--upper<span class="w"> </span><span class="m">1</span><span class="w"> </span>--number<span class="w"> </span><span class="m">1</span><span class="w"> </span>-p<span class="w"> </span>work
<span class="go">Passphrase: [[I am an insecure master passphrase, but easy to type.]]</span>
<span class="go">it90-HPO</span>
</code></pre></div>
<p>This works.
For now.</p>
<h3 id="complication-2-how-to-implement-passphrase-rotation">Complication 2: How to implement passphrase rotation?<a class="headerlink" href="#complication-2-how-to-implement-passphrase-rotation" title="Permanent link">&para;</a></h3>
<p><code>derivepassphrase</code> can only ever derive one passphrase per configuration, so passphrase rotation cannot be accomplished by reusing the same configuration.
So some part of the configuration&mdash;generally the service name&mdash;needs to change upon each rotation.</p>
<div class="admonition abstract">
<p class="admonition-title">Further reading</p>
<p>→ How to deal with regular passphrase rotation (TODO)</p>
</div>
<p>We choose to append a very coarse timestamp to the &ldquo;base&rdquo; service name <code>work</code>: the 4-digit year, a <code>Q</code>, and the &ldquo;quarter&rdquo; number (1, 2, 3 or 4).
As of October 2024, this leads to the final service name <code>work-2024Q4</code>.</p>
<div class="highlight"><pre><span></span><code><span class="gp">$ </span>derivepassphrase<span class="w"> </span>vault<span class="w"> </span>--config<span class="w"> </span>--length<span class="w"> </span><span class="m">8</span><span class="w"> </span>--space<span class="w"> </span><span class="m">0</span><span class="w"> </span>--symbol<span class="w"> </span><span class="m">0</span><span class="w"> </span>--dash<span class="w"> </span><span class="m">1</span><span class="w"> </span><span class="se">\</span>
<span class="gp">&gt; </span><span class="w">                       </span>--upper<span class="w"> </span><span class="m">1</span><span class="w"> </span>--number<span class="w"> </span><span class="m">1</span><span class="w"> </span>work-2024Q4
<span class="gp">$ </span>derivepassphrase<span class="w"> </span>vault<span class="w"> </span>-p<span class="w"> </span>work-2024Q4
<span class="go">Passphrase: [[I am an insecure master passphrase, but easy to type.]]</span>
<span class="go">-P268G0A</span>
</code></pre></div>
<h2 id="summary">Summary<a class="headerlink" href="#summary" title="Permanent link">&para;</a></h2>
<p>We have installed <code>derivepassphrase</code> and set up three accounts for use with the <code>vault</code> passphrase derivation scheme, and the master passphrase <code>I am an insecure master passphrase, but easy to type.</code>.
Our configuration should look like this:</p>
<div class="highlight"><pre><span></span><code><span class="gp">$ </span>derivepassphrase<span class="w"> </span>vault<span class="w"> </span>--export<span class="w"> </span>-
<span class="go">{&quot;services&quot;: {&quot;email&quot;: {&quot;length&quot;: 12, &quot;repeat&quot;: 3, &quot;lower&quot;: 1, &quot;upper&quot;: 1, &quot;number&quot;: 1, &quot;space&quot;: 0}, &quot;bank&quot;: {&quot;length&quot;: 5, &quot;lower&quot;: 0, &quot;upper&quot;: 0, &quot;number&quot;: 5, &quot;space&quot;: 0, &quot;dash&quot;: 0, &quot;symbol&quot;: 0}, &quot;work-2024Q4&quot;: {&quot;length&quot;: 8, &quot;upper&quot;: 1, &quot;number&quot;: 1, &quot;space&quot;: 0, &quot;dash&quot;: 1, &quot;symbol&quot;: 0}}}</span>
</code></pre></div>
<p>We should also get the following output when asking for those passphrases again:</p>
<div class="highlight"><pre><span></span><code><span class="gp">$ </span>derivepassphrase<span class="w"> </span>vault<span class="w"> </span>-p<span class="w"> </span>email
<span class="go">Passphrase: [[I am an insecure master passphrase, but easy to type.]]</span>
<span class="go">kEFwoD=C?@+7</span>
<span class="gp">$ </span>derivepassphrase<span class="w"> </span>vault<span class="w"> </span>-p<span class="w"> </span>bank
<span class="go">Passphrase: [[I am an insecure master passphrase, but easy to type.]]</span>
<span class="go">98517</span>
<span class="gp">$ </span>derivepassphrase<span class="w"> </span>vault<span class="w"> </span>-p<span class="w"> </span>work-2024Q4
<span class="go">Passphrase: [[I am an insecure master passphrase, but easy to type.]]</span>
<span class="go">-P268G0A</span>
</code></pre></div>
<p>This completes the tutorial.</p>

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