97 lines
4.7 KiB
HTML
97 lines
4.7 KiB
HTML
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<!DOCTYPE html>
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<html>
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<head>
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<meta charset="utf-8"/>
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<style>
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table.head, table.foot { width: 100%; }
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td.head-rtitle, td.foot-os { text-align: right; }
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td.head-vol { text-align: center; }
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div.Pp { margin: 1ex 0ex; }
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</style>
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<link rel="stylesheet" href="style.css" type="text/css" media="all"/>
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<title>CRYPTO_IETF_CHACHA20(3MONOCYPHER)</title>
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</head>
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<body>
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<table class="head">
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<tr>
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<td class="head-ltitle">CRYPTO_IETF_CHACHA20(3MONOCYPHER)</td>
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<td class="head-vol">3MONOCYPHER</td>
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<td class="head-rtitle">CRYPTO_IETF_CHACHA20(3MONOCYPHER)</td>
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</tr>
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</table>
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<div class="manual-text">
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<h1 class="Sh" title="Sh" id="NAME"><a class="selflink" href="#NAME">NAME</a></h1>
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<b class="Nm" title="Nm">crypto_ietf_chacha20</b>,
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<b class="Nm" title="Nm">crypto_ietf_chacha20_ctr</b> —
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<span class="Nd" title="Nd">IETF Chacha20 encryption functions</span>
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<h1 class="Sh" title="Sh" id="SYNOPSIS"><a class="selflink" href="#SYNOPSIS">SYNOPSIS</a></h1>
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<b class="In" title="In">#include
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<<a class="In" title="In">monocypher.h</a>></b>
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<div class="Pp"></div>
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<var class="Ft" title="Ft">void</var>
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<br/>
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<b class="Fn" title="Fn">crypto_ietf_chacha20</b>(<var class="Fa" title="Fa">uint8_t
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*cipher_text</var>, <var class="Fa" title="Fa">const uint8_t
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*plain_text</var>, <var class="Fa" title="Fa">size_t text_size</var>,
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<var class="Fa" title="Fa">const uint8_t key[32]</var>,
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<var class="Fa" title="Fa">const uint8_t nonce[12]</var>);
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<div class="Pp"></div>
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<var class="Ft" title="Ft">void</var>
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<br/>
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<b class="Fn" title="Fn">crypto_ietf_chacha20_ctr</b>(<var class="Fa" title="Fa">uint8_t
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*cipher_text</var>, <var class="Fa" title="Fa">const uint8_t
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*plain_text</var>, <var class="Fa" title="Fa">size_t text_size</var>,
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<var class="Fa" title="Fa">const uint8_t key[32]</var>,
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<var class="Fa" title="Fa">const uint8_t nonce[12]</var>,
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<var class="Fa" title="Fa">const uint32_t ctr</var>);
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<h1 class="Sh" title="Sh" id="DESCRIPTION"><a class="selflink" href="#DESCRIPTION">DESCRIPTION</a></h1>
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These functions provide an interface for the Chacha20 encryption primitive as
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specified by the IETF in RFC 8439. They are provided strictly for
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compatibility with existing systems or strict standards compliance. New
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programs are strongly encouraged to use
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<a class="Xr" title="Xr" href="crypto_xchacha20.html">crypto_xchacha20(3monocypher)</a>
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instead.
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<div class="Pp"></div>
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Chacha20 is a low-level primitive. Consider using authenticated encryption,
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implemented by
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<a class="Xr" title="Xr" href="crypto_lock.html">crypto_lock(3monocypher)</a>.
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<div class="Pp"></div>
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The <b class="Fn" title="Fn">crypto_ietf_chacha20</b>() and
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<b class="Fn" title="Fn">crypto_ietf_chacha20_ctr</b>() functions behave the
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same as
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<a class="Xr" title="Xr" href="crypto_chacha20.html">crypto_chacha20</a> and
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<a class="Xr" title="Xr" href="crypto_chacha20_ctr.html">crypto_chacha20_ctr</a>,
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respectively, but use differently-sized nonce and counter values. The nonce
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encompasses 12 bytes and the counter is correspondingly reduced to 4 bytes.
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The short counter limits a single pair of key and nonce to 256 GiB of data. A
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nonce of 12 bytes is <i class="Em" title="Em">just barely too short</i> to be
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safely chosen at random; use a message counter instead. RFC 8439 also permits
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linear feedback shift registers to generate nonces.
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<h1 class="Sh" title="Sh" id="RETURN_VALUES"><a class="selflink" href="#RETURN_VALUES">RETURN
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VALUES</a></h1>
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<b class="Fn" title="Fn">crypto_ietf_chacha20</b>() returns nothing.
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<b class="Fn" title="Fn">crypto_ietf_chacha20_ctr</b>() functions return the
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next <var class="Fa" title="Fa">ctr</var> to use with the same key and nonce
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values; this is always <var class="Fa" title="Fa">text_size</var> divided by
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64; plus one if there was a remainder.
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<h1 class="Sh" title="Sh" id="SEE_ALSO"><a class="selflink" href="#SEE_ALSO">SEE
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ALSO</a></h1>
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<a class="Xr" title="Xr" href="crypto_chacha20.html">crypto_chacha20(3monocypher)</a>,
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<a class="Xr" title="Xr" href="crypto_lock.html">crypto_lock(3monocypher)</a>,
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<a class="Xr" title="Xr" href="crypto_wipe.html">crypto_wipe(3monocypher)</a>,
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<a class="Xr" title="Xr" href="intro.html">intro(3monocypher)</a>
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<h1 class="Sh" title="Sh" id="STANDARDS"><a class="selflink" href="#STANDARDS">STANDARDS</a></h1>
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These functions implement Chacha20 as described in RFC 8439.
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<h1 class="Sh" title="Sh" id="HISTORY"><a class="selflink" href="#HISTORY">HISTORY</a></h1>
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<b class="Fn" title="Fn">crypto_ietf_chacha20</b>() and
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<b class="Fn" title="Fn">crypto_ietf_chacha20_ctr</b>() were added in
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Monocypher 3.0.0.</div>
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<table class="foot">
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<tr>
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<td class="foot-date">March 31, 2020</td>
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<td class="foot-os">Linux 4.15.0-106-generic</td>
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</tr>
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</table>
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</body>
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</html>
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