/* present.c */
/*
    This file is part of the AVR-Crypto-Lib.
    Copyright (C) 2006-2015 Daniel Otte (bg@nerilex.org)

    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/>.
*/
/**
 * present.c
 * a implementation of the PRESENT block-cipher
 * author: Daniel Otte
 * email:  bg@nerilex.org
 * license: GPLv3
 * 
 * */
 
#include <string.h>
#include <stdint.h> 
#include <avr/pgmspace.h>
#include "present_speed.h"

static
void key_update(uint8_t *buffer, uint8_t round){
	uint8_t j;
	union __attribute__((packed)){
		uint8_t   v8[2];
		uint16_t v16;
	} tmp;
	/* rotate buffer 19 right */
	tmp.v16 = ((uint16_t*)buffer)[4];
	j=4;
	do{
		((uint16_t*)buffer)[j] = ((uint16_t*)buffer)[j-1];
	}while(--j);
	((uint16_t*)buffer)[0] = tmp.v16;
	uint8_t t8;
	j=0;
	t8 = (uint16_t)buffer[9] << (5);
	do{
		tmp.v8[1] = buffer[j];
		tmp.v16 >>= 3;
		buffer[j] = tmp.v8[1] | t8;
		t8 = tmp.v8[0] & 0xe0;
	}while(++j<10);
	/* rotating done now substitution */
	buffer[0] = (present_sbox(buffer[0])&0xF0) | ((buffer[0])&0x0F);
	/* xor with round counter */
	buffer[8] ^= round << 7;
	buffer[7] ^= round >> 1;
}

void present_init(const uint8_t *key, uint8_t keysize_b, present_ctx_t *ctx){
	uint8_t i,key_buffer[10];
	memcpy(key_buffer, key, 10);
	memcpy(&(ctx->k[0]), key_buffer, 8);
	for(i=1; i<32; ++i){
		key_update(key_buffer, i);
		memcpy(&(ctx->k[i]), key_buffer, 8);
	}
}


void present_enc(void *buffer, present_ctx_t *ctx){
	uint8_t i,j,tmp[8];
	for(i=0; i<31; ++i){
		*((uint64_t*)buffer) ^= ctx->k[i];
		memxor(buffer, &ctx->k[i], 8);
		j = 7;
		do{
			tmp[j] = present_sbox(((uint8_t*)buffer)[j]);
		}while(j--);
		present_p(buffer, tmp);
	}
	memxor(buffer, &ctx->k[31], 8);
}


void present_dec(void *buffer, present_ctx_t *ctx){
	uint8_t j,tmp[8];
	uint8_t i;
	memxor(buffer, &ctx->k[31], 8);
	i = 30;
	do{
		present_p(tmp, buffer);
		present_p(buffer, tmp);
		j = 7;
		do{
			((uint8_t*)buffer)[j] = present_sbox_inv(((uint8_t*)buffer)[j]);
		}while(j--);
		memxor(buffer, &ctx->k[i], 8);
	}while(i--);
}