132 lines
4.9 KiB
C
132 lines
4.9 KiB
C
/* entropium.c */
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/*
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This file is part of the AVR-Crypto-Lib.
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Copyright (C) 2006-2015 Daniel Otte (bg@nerilex.org)
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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/**
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* \file entropium.c
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* \author Daniel Otte
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* \email bg@nerilex.org
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* \date 2006-05-17
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* \license GPLv3 or later
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* \brief This file contains an implementaition of a pseudo-random-number generator.
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*
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* Extension 1:
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* rndCore is expanded to 512 bits for more security.
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*
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\verbatim
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################################################################################################
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# #
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# +---------------------------+ #
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# | | #
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# V | #
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# (concat) | #
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+---------------+ # o---------o (xor)+---------+ o---------o o----o o---------o # +--------------+
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| entropy Block | -----> | sha-256 | --(offset)-< | rndCore | ---> | sha-256 | --+----| +1 |---> | sha-256 | -----> | random Block |
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+---------------+ # o---------o (xor)+---------+ o---------o | o----o o---------o # +--------------+
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# (xor) (xor) | #
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# ^ ^ | #
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# \ / | #
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# (offset)---------------------+ #
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# #
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################################################################################################
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\endverbatim
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*/
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#include <stdint.h>
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#include <string.h>
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#include "sha256.h"
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#include "entropium.h"
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/**
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* \brief secret entropy pool.
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* This is the core of the random which is generated
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*/
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uint32_t rndCore[16];
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/*************************************************************************/
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/* idea is: hash the message and add it via xor to rndCore
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*
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* length in bits
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*
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* we simply first "hash" rndCore, then entropy.
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*/
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void entropium_addEntropy(unsigned length_b, const void *data){
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sha256_ctx_t s;
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static uint8_t offset=0; /* selects if higher or lower half gets updated */
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sha256_init(&s);
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sha256_nextBlock(&s, rndCore);
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while (length_b>=512){
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sha256_nextBlock(&s, data);
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data = (uint8_t*)data+ 512/8;
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length_b -= 512;
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}
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sha256_lastBlock(&s, data, length_b);
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uint8_t i;
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for (i=0; i<8; ++i){
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rndCore[i+offset] ^= s.h[i];
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}
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offset ^= 8; /* hehe */
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}
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/*************************************************************************/
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void entropium_getRandomBlock(void *b){
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sha256_ctx_t s;
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static uint8_t offset=8;
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sha256_init(&s);
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sha256_lastBlock(&s, rndCore, 512); /* remeber the byte order! */
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uint8_t i;
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for (i=0; i<8; ++i){
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rndCore[i+offset] ^= s.h[i];
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}
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offset ^= 8; /* hehe */
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memcpy(b, s.h, 32); /* back up first hash in b */
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((uint8_t*)b)[*((uint8_t*)b)&31]++; /* the important increment step */
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sha256_init(&s);
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sha256_lastBlock(&s, b, 256);
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memcpy(b, s.h, 32);
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}
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/*************************************************************************/
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uint8_t entropium_getRandomByte(void){
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static uint8_t block[32];
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static uint8_t i=32;
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if (i==32){
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entropium_getRandomBlock((void*)block);
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i=0;
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}
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return block[i++];
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}
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void entropium_fillBlockRandom(void *block, unsigned length_B){
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while(length_B>ENTROPIUM_RANDOMBLOCK_SIZE){
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entropium_getRandomBlock(block);
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block = (uint8_t*)block + ENTROPIUM_RANDOMBLOCK_SIZE;
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length_B -= ENTROPIUM_RANDOMBLOCK_SIZE;
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}
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while(length_B){
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*((uint8_t*)block) = entropium_getRandomByte();
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block= (uint8_t*)block +1; --length_B;
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}
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}
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