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</pre><pre class="rust"><code><span class="comment">// Copyright 2015-2019 Brian Smith.
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED &quot;AS IS&quot; AND THE AUTHORS DISCLAIM ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
</span><span class="kw">use crate</span>::{digest, error, limb};
<span class="kw">use </span>core::convert::TryInto;
<span class="attribute">#[repr(transparent)]
</span><span class="kw">pub struct </span>Scalar([u8; SCALAR_LEN]);
<span class="kw">pub const </span>SCALAR_LEN: usize = <span class="number">32</span>;
<span class="kw">impl </span>Scalar {
<span class="comment">// Constructs a `Scalar` from `bytes`, failing if `bytes` encodes a scalar
// that not in the range [0, n).
</span><span class="kw">pub fn </span>from_bytes_checked(bytes: [u8; SCALAR_LEN]) -&gt; <span class="prelude-ty">Result</span>&lt;<span class="self">Self</span>, error::Unspecified&gt; {
<span class="kw">const </span>ORDER: [limb::Limb; SCALAR_LEN / limb::LIMB_BYTES] =
<span class="macro">limbs!</span>[<span class="number">0x5cf5d3ed</span>, <span class="number">0x5812631a</span>, <span class="number">0xa2f79cd6</span>, <span class="number">0x14def9de</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0x10000000</span>];
<span class="comment">// `bytes` is in little-endian order.
</span><span class="kw">let </span><span class="kw-2">mut </span>reversed = bytes;
reversed.reverse();
<span class="kw">let </span><span class="kw-2">mut </span>limbs = [<span class="number">0</span>; SCALAR_LEN / limb::LIMB_BYTES];
limb::parse_big_endian_in_range_and_pad_consttime(
untrusted::Input::from(<span class="kw-2">&amp;</span>reversed),
limb::AllowZero::Yes,
<span class="kw-2">&amp;</span>ORDER,
<span class="kw-2">&amp;mut </span>limbs,
)<span class="question-mark">?</span>;
<span class="prelude-val">Ok</span>(<span class="self">Self</span>(bytes))
}
<span class="comment">// Constructs a `Scalar` from `digest` reduced modulo n.
</span><span class="kw">pub fn </span>from_sha512_digest_reduced(digest: digest::Digest) -&gt; <span class="self">Self </span>{
<span class="kw">extern </span><span class="string">&quot;C&quot; </span>{
<span class="kw">fn </span>GFp_x25519_sc_reduce(s: <span class="kw-2">&amp;mut </span>UnreducedScalar);
}
<span class="kw">let </span><span class="kw-2">mut </span>unreduced = [<span class="number">0u8</span>; digest::SHA512_OUTPUT_LEN];
unreduced.copy_from_slice(digest.as_ref());
<span class="kw">unsafe </span>{ GFp_x25519_sc_reduce(<span class="kw-2">&amp;mut </span>unreduced) };
<span class="self">Self</span>((<span class="kw-2">&amp;</span>unreduced[..SCALAR_LEN]).try_into().unwrap())
}
}
<span class="attribute">#[repr(transparent)]
</span><span class="kw">pub struct </span>MaskedScalar([u8; SCALAR_LEN]);
<span class="kw">impl </span>MaskedScalar {
<span class="kw">pub fn </span>from_bytes_masked(bytes: [u8; SCALAR_LEN]) -&gt; <span class="self">Self </span>{
<span class="kw">extern </span><span class="string">&quot;C&quot; </span>{
<span class="kw">fn </span>GFp_x25519_sc_mask(a: <span class="kw-2">&amp;mut </span>[u8; SCALAR_LEN]);
}
<span class="kw">let </span><span class="kw-2">mut </span>r = <span class="self">Self</span>(bytes);
<span class="kw">unsafe </span>{ GFp_x25519_sc_mask(<span class="kw-2">&amp;mut </span>r.<span class="number">0</span>) };
r
}
}
<span class="kw">impl </span>From&lt;MaskedScalar&gt; <span class="kw">for </span>Scalar {
<span class="kw">fn </span>from(MaskedScalar(scalar): MaskedScalar) -&gt; <span class="self">Self </span>{
<span class="self">Self</span>(scalar)
}
}
<span class="kw">type </span>UnreducedScalar = [u8; UNREDUCED_SCALAR_LEN];
<span class="kw">const </span>UNREDUCED_SCALAR_LEN: usize = SCALAR_LEN * <span class="number">2</span>;
</code></pre></div>
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