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200 lines
7.1 KiB
C
200 lines
7.1 KiB
C
/* ec_dh.c - TinyCrypt implementation of EC-DH */
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/*
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* Copyright (c) 2014, Kenneth MacKay
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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* * Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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* Copyright (C) 2017 by Intel Corporation, All Rights Reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* - Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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*
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* - Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* - Neither the name of Intel Corporation nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <tinycrypt/ecc.h>
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#include <tinycrypt/ecc_dh.h>
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#include <string.h>
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#if default_RNG_defined
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static uECC_RNG_Function g_rng_function = &default_CSPRNG;
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#else
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static uECC_RNG_Function g_rng_function = 0;
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#endif
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int uECC_make_key_with_d(uint8_t *public_key, uint8_t *private_key,
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unsigned int *d, uECC_Curve curve)
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{
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uECC_word_t _private[NUM_ECC_WORDS];
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uECC_word_t _public[NUM_ECC_WORDS * 2];
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/* This function is designed for test purposes-only (such as validating NIST
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* test vectors) as it uses a provided value for d instead of generating
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* it uniformly at random. */
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memcpy (_private, d, NUM_ECC_BYTES);
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/* Computing public-key from private: */
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if (EccPoint_compute_public_key(_public, _private, curve)) {
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/* Converting buffers to correct bit order: */
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uECC_vli_nativeToBytes(private_key,
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BITS_TO_BYTES(curve->num_n_bits),
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_private);
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uECC_vli_nativeToBytes(public_key,
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curve->num_bytes,
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_public);
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uECC_vli_nativeToBytes(public_key + curve->num_bytes,
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curve->num_bytes,
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_public + curve->num_words);
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/* erasing temporary buffer used to store secret: */
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memset(_private, 0, NUM_ECC_BYTES);
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return 1;
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}
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return 0;
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}
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int uECC_make_key(uint8_t *public_key, uint8_t *private_key, uECC_Curve curve)
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{
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uECC_word_t _random[NUM_ECC_WORDS * 2];
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uECC_word_t _private[NUM_ECC_WORDS];
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uECC_word_t _public[NUM_ECC_WORDS * 2];
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uECC_word_t tries;
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for (tries = 0; tries < uECC_RNG_MAX_TRIES; ++tries) {
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/* Generating _private uniformly at random: */
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uECC_RNG_Function rng_function = uECC_get_rng();
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if (!rng_function ||
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!rng_function((uint8_t *)_random, 2 * NUM_ECC_WORDS*uECC_WORD_SIZE)) {
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return 0;
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}
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/* computing modular reduction of _random (see FIPS 186.4 B.4.1): */
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uECC_vli_mmod(_private, _random, curve->n, BITS_TO_WORDS(curve->num_n_bits));
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/* Computing public-key from private: */
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if (EccPoint_compute_public_key(_public, _private, curve)) {
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/* Converting buffers to correct bit order: */
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uECC_vli_nativeToBytes(private_key,
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BITS_TO_BYTES(curve->num_n_bits),
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_private);
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uECC_vli_nativeToBytes(public_key,
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curve->num_bytes,
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_public);
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uECC_vli_nativeToBytes(public_key + curve->num_bytes,
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curve->num_bytes,
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_public + curve->num_words);
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/* erasing temporary buffer that stored secret: */
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memset(_private, 0, NUM_ECC_BYTES);
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return 1;
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}
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}
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return 0;
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}
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int uECC_shared_secret(const uint8_t *public_key, const uint8_t *private_key,
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uint8_t *secret, uECC_Curve curve)
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{
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uECC_word_t _public[NUM_ECC_WORDS * 2];
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uECC_word_t _private[NUM_ECC_WORDS];
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uECC_word_t tmp[NUM_ECC_WORDS];
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uECC_word_t *p2[2] = {_private, tmp};
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uECC_word_t *initial_Z = 0;
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uECC_word_t carry;
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wordcount_t num_words = curve->num_words;
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wordcount_t num_bytes = curve->num_bytes;
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int r;
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/* Converting buffers to correct bit order: */
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uECC_vli_bytesToNative(_private,
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private_key,
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BITS_TO_BYTES(curve->num_n_bits));
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uECC_vli_bytesToNative(_public,
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public_key,
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num_bytes);
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uECC_vli_bytesToNative(_public + num_words,
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public_key + num_bytes,
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num_bytes);
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/* Regularize the bitcount for the private key so that attackers cannot use a
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* side channel attack to learn the number of leading zeros. */
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carry = regularize_k(_private, _private, tmp, curve);
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/* If an RNG function was specified, try to get a random initial Z value to
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* improve protection against side-channel attacks. */
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if (g_rng_function) {
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if (!uECC_generate_random_int(p2[carry], curve->p, num_words)) {
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r = 0;
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goto clear_and_out;
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}
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initial_Z = p2[carry];
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}
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EccPoint_mult(_public, _public, p2[!carry], initial_Z, curve->num_n_bits + 1,
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curve);
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uECC_vli_nativeToBytes(secret, num_bytes, _public);
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r = !EccPoint_isZero(_public, curve);
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clear_and_out:
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/* erasing temporary buffer used to store secret: */
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memset(p2, 0, sizeof(p2));
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__asm__ __volatile__("" :: "g"(p2) : "memory");
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memset(tmp, 0, sizeof(tmp));
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__asm__ __volatile__("" :: "g"(tmp) : "memory");
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memset(_private, 0, sizeof(_private));
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__asm__ __volatile__("" :: "g"(_private) : "memory");
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return r;
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}
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