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<title>
libntruprime: Intro</title>
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libntruprime</div>
<div class="navt here">Intro
</div><div class="navt away"><a href=download.html>Download</a>
</div><div class="navt away"><a href=install.html>Install</a>
</div><div class="navt away"><a href=test.html>Test</a>
</div><div class="navt away"><a href=api.html>API</a>
</div><div class="navt away"><a href=cli.html>CLI</a>
</div><div class="navt away"><a href=security.html>Security</a>
</div><div class="navt away"><a href=verification.html>Verification</a>
</div><div class="navt away"><a href=speed.html>Speed</a>
</div><div class="navt away"><a href=internals.html>Internals</a>
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<div class=pagetitle>libntruprime: Intro</div>
<p>libntruprime is a microlibrary for the
<a href="https://ntruprime.cr.yp.to">Streamlined NTRU Prime</a>
cryptosystem.
Streamlined NTRU Prime (<code>sntrup</code>) is a lattice-based cryptosystem with the following features:</p>
<ul>
<li>Stability:
Almost all details of <code>sntrup</code> match a
<a href="https://ntruprime.cr.yp.to/ntruprime-20160511.pdf">May 2016</a> publication.
The only exceptions are small changes to encoding and hashing published in
<a href="https://ntruprime.cr.yp.to/nist/ntruprime-20190330.pdf">April 2019</a>.</li>
<li>Patent-freeness:
April 2019 predates almost all
<a href="https://patents.google.com/?q=(%22post-quantum%22)">post-quantum patents</a>.
Analyses of various <a href="https://ntruprime.cr.yp.to/faq.html">lattice patents</a>
filed before April 2019 indicate no problems for <code>sntrup</code>.</li>
<li>Deployment:
The popular OpenSSH tool switched to <code>sntrup761</code> by default
in <a href="https://www.openssh.com/txt/release-9.0">April 2022</a>,
following initial integration of <code>sntrup</code> into <a href="https://github.com/janmojzis/tinyssh">TinySSH</a>.</li>
<li>Affordability:
Keys and ciphertexts are <a href="https://ntruprime.cr.yp.to/speed.html">about 1KB</a>
for <code>sntrup761</code>,
and computations are <a href="speed.html">fast</a>.</li>
<li>Careful design:
Subject to the requirement of being a small lattice-based cryptosystem,
<code>sntrup</code> is systematically designed to
<a href="https://ntruprime.cr.yp.to/">eliminate unnecessary complications in security review</a>.
It eliminates decryption failures, for example, and eliminates cyclotomics.
The cryptosystem has never needed a security patch.</li>
<li>Risk management: A much higher <code>sntrup1277</code> security level is
<a href="https://ntruprime.cr.yp.to/speed.html">fully supported</a>,
and is recommended whenever 2KB keys and ciphertexts are affordable,
to reduce risks from
<a href="https://ntruprime.cr.yp.to/warnings.html">improvements in lattice attacks</a>.</li>
<li>Flexibility:
The <code>sntrup</code> design allows a full spectrum of tradeoffs between size and security level,
so applications with intermediate size limits aren't forced into much lower security levels.
<a href="https://ntruprime.cr.yp.to/speed.html">Six different sizes</a>
have been selected for support.</li>
</ul>
<p>libntruprime has a very simple stateless <a href="api.html">API</a>
based on the SUPERCOP API,
with wire-format inputs and outputs,
providing functions
that directly match the KEM operations provided by the <code>sntrup</code> specification,
such as functions</p>
<pre><code>sntrup1277_keypair
sntrup1277_enc
sntrup1277_dec
</code></pre>
<p>for the <code>sntrup1277</code> KEM.</p>
<p>Internally,
libntruprime includes implementations designed to work portably across CPUs,
and implementations designed for <a href="speed.html">higher performance</a>
on Intel/AMD CPUs with AVX2 instructions.
libntruprime includes automatic run-time selection of implementations.</p>
<p>libntruprime is intended to be
called by larger multi-function libraries
(such as traditional cryptographic libraries),
including libraries in other languages via FFI.
The idea is that libntruprime takes responsibility
for the details of <code>sntrup</code> computation,
including optimization, timing-attack protection, and (in ongoing work) verification,
freeing up the calling libraries to concentrate on
application-specific needs such as protocol integration.
Applications can also call libntruprime directly.</p><hr><font size=1><b>Version:</b>
This is version 2024.08.25 of the "Intro" web page.
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