51 lines
1.1 KiB
C
51 lines
1.1 KiB
C
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/* LibTomCrypt, modular cryptographic library -- Tom St Denis
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*
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* LibTomCrypt is a library that provides various cryptographic
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* algorithms in a highly modular and flexible manner.
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*
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* The library is free for all purposes without any express
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* guarantee it works.
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*
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* Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.org
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*/
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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.h"
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#if defined(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(gcm_state *gcm, unsigned char *I)
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{
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unsigned char T[16];
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#ifdef GCM_TABLES
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int x, 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 *)(T + y)) ^= *((LTC_FAST_TYPE *)(&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
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}
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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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/* $Source$ */
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/* $Revision$ */
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/* $Date$ */
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