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/* Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
* SPDX-License-Identifier: Apache-2.0"
*
* Written by Nir Drucker and Shay Gueron
* AWS Cryptographic Algorithms Group.
* (ndrucker@amazon.com, gueron@amazon.com)
*/
#include "sampling.h"
#include <assert.h>
#define MAX_WEIGHT (T1 > DV ? T1 : DV)
// This implementation assumes that the wlist contains fake list
void
secure_set_bits(IN OUT uint64_t * a,
IN const idx_t wlist[],
IN const uint32_t a_len_bytes,
IN const uint32_t weight)
{
assert(a_len_bytes % 8 == 0);
// Set arrays to the maximum possible for the stack protector
assert(weight <= MAX_WEIGHT);
uint64_t qw_pos[MAX_WEIGHT];
uint64_t bit_pos[MAX_WEIGHT];
// 1. Identify the QW position of each value and the bit position inside this
// QW.
for(uint32_t j = 0; j < weight; j++)
{
qw_pos[j] = wlist[j] >> 6;
bit_pos[j] = BIT(wlist[j] & 0x3f);
}
// 2. Fill each QW in a constant time.
for(uint32_t qw = 0; qw < (a_len_bytes / 8); qw++)
{
uint64_t tmp = 0;
for(uint32_t j = 0; j < weight; j++)
{
uint64_t mask = (-1ULL) + (!secure_cmp32(qw_pos[j], qw));
tmp |= (bit_pos[j] & mask);
}
// Set the bit in a masked way
a[qw] |= tmp;
}
}
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