86 lines
3.8 KiB
HTML
86 lines
3.8 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_X25519_INVERSE(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_X25519_INVERSE(3MONOCYPHER)</td>
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<td class="head-vol">3MONOCYPHER</td>
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<td class="head-rtitle">CRYPTO_X25519_INVERSE(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_x25519_inverse</b> —
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<span class="Nd" title="Nd">X25519 scalar multiplication with the
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multiplicative inverse of a scalar</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_x25519_inverse</b>(<var class="Fa" title="Fa">uint8_t
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blind_salt[32]</var>, <var class="Fa" title="Fa">const uint8_t
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private_key[32]</var>, <var class="Fa" title="Fa">const uint8_t
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curve_point</var>);
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<h1 class="Sh" title="Sh" id="DESCRIPTION"><a class="selflink" href="#DESCRIPTION">DESCRIPTION</a></h1>
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The <b class="Fn" title="Fn">crypto_x25519_inverse</b>() function performs
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scalar multiplication of the multiplicative inverse of a scalar for X25519.
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<b class="Sy" title="Sy">This is a highly advanced, specialized feature</b>;
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unless you are implementing a protocol that requires this specifically,
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<b class="Sy" title="Sy">you likely have no reason to be using these
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functions</b> and are probably looking for
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<a class="Xr" title="Xr" href="crypto_key_exchange.html">crypto_key_exchange(3monocypher)</a>
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or
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<a class="Xr" title="Xr" href="crypto_x25519.html">crypto_x25519(3monocypher)</a>
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instead. Expect elliptic curve jargon on this page.
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<div class="Pp"></div>
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This function is used, for example, with exponential blinding in oblivious
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pseudo-random functions (OPRFs). 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">blind_salt</var></dt>
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<dd class="It-tag">The output point.</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">private_key</var></dt>
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<dd class="It-tag">The private key (scalar) to use. First, the value is
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clamped; then the clamped value's multiplicative inverse (modulo the curve
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order) is determined; the clamped value's multiplicative inverse then has
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its cofactor cleared, and that final value is then used for scalar
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multiplication.</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">curve_point</var></dt>
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<dd class="It-tag">The curve point on X25519 to multiply with the
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multiplicative inverse (modulo the curve order) of
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<var class="Fa" title="Fa">private_key</var>.</dd>
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</dl>
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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_x25519.html">crypto_x25519(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="HISTORY"><a class="selflink" href="#HISTORY">HISTORY</a></h1>
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The <b class="Fn" title="Fn">crypto_x25519_inverse</b>() function first appeared
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in Monocypher 3.1.0.</div>
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<table class="foot">
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<tr>
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<td class="foot-date">March 24, 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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