86 lines
2.3 KiB
C
86 lines
2.3 KiB
C
/*
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* Copyright (c) 2024 Lucas Gabriel Vuotto <lucas@lgv5.net>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include <stddef.h>
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#include <stdint.h>
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#include "impl_chacha20.h"
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#include "util.h"
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/*
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* ChaCha20 implementation.
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*
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* ChaCha originally designed by Daniel J. Bernstein, "ChaCha, a variant of
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* Salsa20", https://cr.yp.to/chacha/chacha-20080128.pdf .
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*/
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/* "expand 32-byte k" */
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#define SIGMA0 UINT32_C(0x61707865)
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#define SIGMA1 UINT32_C(0x3320646e)
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#define SIGMA2 UINT32_C(0x79622d32)
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#define SIGMA3 UINT32_C(0x6b206574)
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#define QUARTERROUND(a, b, c, d) do { \
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a += b; d ^= a; d = rotl32(d, 16); \
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c += d; b ^= c; b = rotl32(b, 12); \
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a += b; d ^= a; d = rotl32(d, 8); \
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c += d; b ^= c; b = rotl32(b, 7); \
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} while (0)
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void
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chacha20_block(struct chacha20_ctx *ctx)
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{
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uint32_t x[CHACHA20_CHUNK_WORDS];
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size_t i;
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x[0] = SIGMA0;
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x[1] = SIGMA1;
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x[2] = SIGMA2;
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x[3] = SIGMA3;
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x[4] = ctx->k[0];
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x[5] = ctx->k[1];
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x[6] = ctx->k[2];
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x[7] = ctx->k[3];
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x[8] = ctx->k[4];
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x[9] = ctx->k[5];
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x[10] = ctx->k[6];
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x[11] = ctx->k[7];
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x[12] = ctx->c;
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x[13] = ctx->n[0];
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x[14] = ctx->n[1];
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x[15] = ctx->n[2];
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for (i = 0; i < CHACHA20_CHUNK_WORDS; i++)
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ctx->s[i] = x[i];
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for (i = 0; i < CHACHA20_ROUNDS; i++) {
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QUARTERROUND(x[0], x[4], x[8], x[12]);
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QUARTERROUND(x[1], x[5], x[9], x[13]);
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QUARTERROUND(x[2], x[6], x[10], x[14]);
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QUARTERROUND(x[3], x[7], x[11], x[15]);
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QUARTERROUND(x[0], x[5], x[10], x[15]);
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QUARTERROUND(x[1], x[6], x[11], x[12]);
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QUARTERROUND(x[2], x[7], x[8], x[13]);
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QUARTERROUND(x[3], x[4], x[9], x[14]);
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}
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for (i = 0; i < CHACHA20_CHUNK_WORDS; i++)
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ctx->s[i] += x[i];
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}
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