X-Git-Url: https://git.cryptolib.org/?p=avr-crypto-lib.git;a=blobdiff_plain;f=aes%2Faes_dec.c;fp=aes%2Faes_dec.c;h=8c476de0dbe70d3105eda6412befb75f334e78ba;hp=0000000000000000000000000000000000000000;hb=4f50c75ee5a6cc88bf7ea71957ed509e298e6c25;hpb=7701e318e4e2bac7f84dbf6e368f1501814948fc

diff --git a/aes/aes_dec.c b/aes/aes_dec.c
new file mode 100644
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--- /dev/null
+++ b/aes/aes_dec.c
@@ -0,0 +1,131 @@
+/* aes.c */
+/*
+    This file is part of the AVR-Crypto-Lib.
+    Copyright (C) 2008, 2009  Daniel Otte (daniel.otte@rub.de)
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <stdint.h>
+#include <string.h>
+#include "gf256mul.h"
+#include "aes.h"
+#include "aes_invsbox.h"
+#include "aes_dec.h"
+#include <avr/pgmspace.h>
+
+void aes_invshiftrow(void* data, uint8_t shift){
+	uint8_t tmp[4];
+	tmp[0] = ((uint8_t*)data)[(4+0-shift)&3];
+	tmp[1] = ((uint8_t*)data)[(4+1-shift)&3];
+	tmp[2] = ((uint8_t*)data)[(4+2-shift)&3];
+	tmp[3] = ((uint8_t*)data)[(4+3-shift)&3];
+	memcpy(data, tmp, 4);
+}
+
+void aes_invshiftcol(void* data, uint8_t shift){
+	uint8_t tmp[4];
+	tmp[0] = ((uint8_t*)data)[ 0];
+	tmp[1] = ((uint8_t*)data)[ 4];
+	tmp[2] = ((uint8_t*)data)[ 8];
+	tmp[3] = ((uint8_t*)data)[12];
+	((uint8_t*)data)[ 0] = tmp[(4-shift+0)&3];
+	((uint8_t*)data)[ 4] = tmp[(4-shift+1)&3];
+	((uint8_t*)data)[ 8] = tmp[(4-shift+2)&3];
+	((uint8_t*)data)[12] = tmp[(4-shift+3)&3];
+}
+static
+void aes_dec_round(aes_cipher_state_t* state, const aes_roundkey_t* k){
+	uint8_t tmp[16];
+	uint8_t i;
+	uint8_t t,u,v,w;
+	/* keyAdd */
+	for(i=0; i<16; ++i){
+		tmp[i] = state->s[i] ^ k->ks[i];
+	}
+	/* mixColums */
+	for(i=0; i<4; ++i){
+		t = tmp[4*i+3] ^ tmp[4*i+2];
+		u = tmp[4*i+1] ^ tmp[4*i+0];
+		v = t ^ u;
+		v = gf256mul(0x09, v, 0x1b);
+		w = v ^ gf256mul(0x04, tmp[4*i+2] ^ tmp[4*i+0], 0x1b);
+		v = v ^ gf256mul(0x04, tmp[4*i+3] ^ tmp[4*i+1], 0x1b);
+		state->s[4*i+3] = tmp[4*i+3] ^ v ^ gf256mul(0x02, tmp[4*i+0] ^ tmp[4*i+3], 0x1b);
+		state->s[4*i+2] = tmp[4*i+2] ^ w ^ gf256mul(0x02, t, 0x1b);
+		state->s[4*i+1] = tmp[4*i+1] ^ v ^ gf256mul(0x02, tmp[4*i+2] ^ tmp[4*i+1], 0x1b);
+		state->s[4*i+0] = tmp[4*i+0] ^ w ^ gf256mul(0x02, u, 0x1b);
+		
+		/*
+		state->s[4*i+0] =
+			  gf256mul(0xe, tmp[4*i+0], 0x1b)
+			^ gf256mul(0xb, tmp[4*i+1], 0x1b)
+			^ gf256mul(0xd, tmp[4*i+2], 0x1b)
+			^ gf256mul(0x9, tmp[4*i+3], 0x1b);
+		state->s[4*i+1] =
+			  gf256mul(0x9, tmp[4*i+0], 0x1b)
+			^ gf256mul(0xe, tmp[4*i+1], 0x1b)
+			^ gf256mul(0xb, tmp[4*i+2], 0x1b)
+			^ gf256mul(0xd, tmp[4*i+3], 0x1b);
+		state->s[4*i+2] =
+			  gf256mul(0xd, tmp[4*i+0], 0x1b)
+			^ gf256mul(0x9, tmp[4*i+1], 0x1b)
+			^ gf256mul(0xe, tmp[4*i+2], 0x1b)
+			^ gf256mul(0xb, tmp[4*i+3], 0x1b);
+		state->s[4*i+3] =
+			  gf256mul(0xb, tmp[4*i+0], 0x1b)
+			^ gf256mul(0xd, tmp[4*i+1], 0x1b)
+			^ gf256mul(0x9, tmp[4*i+2], 0x1b)
+			^ gf256mul(0xe, tmp[4*i+3], 0x1b);
+		*/
+	}	
+	/* shiftRows */
+	aes_invshiftcol(state->s+1, 1);
+	aes_invshiftcol(state->s+2, 2);
+	aes_invshiftcol(state->s+3, 3);		
+	/* subBytes */
+	for(i=0; i<16; ++i){
+		state->s[i] = pgm_read_byte(aes_invsbox+state->s[i]);
+	}
+}
+
+
+static
+void aes_dec_firstround(aes_cipher_state_t* state, const aes_roundkey_t* k){
+	uint8_t i;
+	/* keyAdd */
+	for(i=0; i<16; ++i){
+		state->s[i] ^= k->ks[i];
+	}
+	/* shiftRows */
+	aes_invshiftcol(state->s+1, 1);
+	aes_invshiftcol(state->s+2, 2);
+	aes_invshiftcol(state->s+3, 3);		
+	/* subBytes */
+	for(i=0; i<16; ++i){
+		state->s[i] = pgm_read_byte(aes_invsbox+state->s[i]);
+	}
+}
+
+void aes_decrypt_core(aes_cipher_state_t* state, const aes_genctx_t* ks, uint8_t rounds){
+	uint8_t i;
+	aes_dec_firstround(state, &(ks->key[i=rounds]));
+	for(;rounds>1;--rounds){
+		--i;
+		aes_dec_round(state, &(ks->key[i]));
+	}
+	for(i=0; i<16; ++i){
+		state->s[i] ^= ks->key[0].ks[i];
+	}
+}