111 lines
4.9 KiB
HTML
111 lines
4.9 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_HCHACHA20(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_HCHACHA20(3MONOCYPHER)</td>
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<td class="head-vol">3MONOCYPHER</td>
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<td class="head-rtitle">CRYPTO_HCHACHA20(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_hchacha20</b> —
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<span class="Nd" title="Nd">HChacha20 special-purpose hashing</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_hchacha20</b>(<var class="Fa" title="Fa">uint8_t
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out[32]</var>, <var class="Fa" title="Fa">const uint8_t key[32]</var>,
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<var class="Fa" title="Fa">const uint8_t in[16]</var>);
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<h1 class="Sh" title="Sh" id="DESCRIPTION"><a class="selflink" href="#DESCRIPTION">DESCRIPTION</a></h1>
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<b class="Fn" title="Fn">crypto_hchacha20</b>() provides a not-so-cryptographic
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hash. It may be used for some specific purposes, such as X25519 key
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derivation, or XChacha20 initialisation. If in doubt, do not use directly. Use
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<a class="Xr" title="Xr" href="crypto_blake2b.html">crypto_blake2b(3monocypher)</a>
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instead.
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<div class="Pp"></div>
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The arguments are:
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<dl class="Bl-tag">
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<dt class="It-tag"> </dt>
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<dd class="It-tag"> </dd>
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<dt class="It-tag"><var class="Fa" title="Fa">key</var></dt>
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<dd class="It-tag">A sufficiently random key, such as the output of
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<a class="Xr" title="Xr" href="crypto_x25519.html">crypto_x25519(3monocypher)</a>.</dd>
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<dt class="It-tag"> </dt>
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<dd class="It-tag"> </dd>
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<dt class="It-tag"><var class="Fa" title="Fa">in</var></dt>
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<dd class="It-tag">The space reserved for the Chacha20 nonce and counter. It
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does not have to be random.</dd>
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<dt class="It-tag"> </dt>
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<dd class="It-tag"> </dd>
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<dt class="It-tag"><var class="Fa" title="Fa">out</var></dt>
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<dd class="It-tag">A cryptographically secure random number
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<i class="Em" title="Em">if</i> there is enough entropy in
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<var class="Fa" title="Fa">key</var>. X25519 shared secrets have enough
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entropy.</dd>
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</dl>
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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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This function returns nothing.
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<h1 class="Sh" title="Sh" id="EXAMPLES"><a class="selflink" href="#EXAMPLES">EXAMPLES</a></h1>
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The following example assumes the existence of
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<b class="Fn" title="Fn">arc4random_buf</b>(), which fills the given buffer
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with cryptographically secure random bytes. If
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<b class="Fn" title="Fn">arc4random_buf</b>() does not exist on your system,
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see <a class="Xr" title="Xr" href="intro.html">intro(3monocypher)</a> for
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advice about how to generate cryptographically secure random bytes.
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<div class="Pp"></div>
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Simple hash:
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<div class="Pp"></div>
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<div class="Bd" style="margin-left: 5.00ex;">
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<pre class="Li">
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uint8_t key[32]; /* Must have enough entropy */
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uint8_t in [16]; /* Does not have to be random */
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uint8_t out[32]; /* Will be random iff the above holds */
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arc4random_buf(key, 32);
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crypto_hchacha20(out, key, in);
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/* Wipe secrets if they are no longer needed */
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crypto_wipe(key, 32);
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crypto_wipe(in , 16);
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</pre>
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</div>
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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_encrypt.html">crypto_chacha20_encrypt(3monocypher)</a>,
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<a class="Xr" title="Xr" href="crypto_key_exchange.html">crypto_key_exchange(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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This function implements HChacha20. HChacha20 derives from Chacha20 the same way
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HSalsa20 derives from Salsa20.
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<h1 class="Sh" title="Sh" id="HISTORY"><a class="selflink" href="#HISTORY">HISTORY</a></h1>
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The <b class="Fn" title="Fn">crypto_hchacha20</b>() function first appeared in
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Monocypher 0.1 as <b class="Fn" title="Fn">crypto_chacha20_H</b>(). It was
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renamed to <b class="Fn" title="Fn">crypto_hchacha20</b>() in Monocypher
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3.0.0.
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<h1 class="Sh" title="Sh" id="CAVEATS"><a class="selflink" href="#CAVEATS">CAVEATS</a></h1>
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<b class="Sy" title="Sy">This is not a general-purpose cryptographic hash
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function</b>.</div>
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<table class="foot">
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<tr>
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<td class="foot-date">March 2, 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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