48 lines
1.2 KiB
C
48 lines
1.2 KiB
C
/* LibTomCrypt, modular cryptographic library -- Tom St Denis */
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/* SPDX-License-Identifier: Unlicense */
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/**
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@file gcm_mult_h.c
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GCM implementation, do the GF mult, by Tom St Denis
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*/
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#include "tomcrypt_private.h"
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#if defined(LTC_GCM_MODE)
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/**
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GCM multiply by H
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@param gcm The GCM state which holds the H value
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@param I The value to multiply H by
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*/
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void gcm_mult_h(const gcm_state *gcm, unsigned char *I)
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{
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unsigned char T[16];
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#ifdef LTC_GCM_TABLES
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int x;
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#ifdef LTC_GCM_TABLES_SSE2
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__asm__("movdqa (%0),%%xmm0"::"r"(&gcm->PC[0][I[0]][0]));
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for (x = 1; x < 16; x++) {
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__asm__("pxor (%0),%%xmm0"::"r"(&gcm->PC[x][I[x]][0]));
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}
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__asm__("movdqa %%xmm0,(%0)"::"r"(&T));
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#else
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int y;
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XMEMCPY(T, &gcm->PC[0][I[0]][0], 16);
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for (x = 1; x < 16; x++) {
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#ifdef LTC_FAST
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for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) {
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*(LTC_FAST_TYPE_PTR_CAST(T + y)) ^= *(LTC_FAST_TYPE_PTR_CAST(&gcm->PC[x][I[x]][y]));
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}
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#else
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for (y = 0; y < 16; y++) {
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T[y] ^= gcm->PC[x][I[x]][y];
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}
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#endif /* LTC_FAST */
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}
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#endif /* LTC_GCM_TABLES_SSE2 */
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#else
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gcm_gf_mult(gcm->H, I, T);
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#endif
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XMEMCPY(I, T, 16);
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}
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#endif
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