prng renamed to entropium

[avr-crypto-lib.git] / entropium.c

diff --git a/entropium.c b/entropium.c
new file mode 100644 (file)
index 0000000..db143cb
--- /dev/null
+++ b/entropium.c
@@ -0,0 +1,152 @@
+/**
+ * \file               entropium.c
+ * \author             Daniel Otte
+ * \date               17.05.2006
+ * \par License:
+ *     GPL
+ * \brief      This file contains an implementaition of a pseudo-random-number generator.
+ * 
+ * Extension 1:
+ *     rndCore is expanded to 512 bits for more security.
+ *
+ * \verbatim
+ *                      ################################################################################################
+ *                      #                                                                                              #
+ *                      #         +---------------------------+                                                        #
+ *                      #         |                           |                             +---+                      #
+ *                      #         V                           |                             |   |                      #
+ *                      #      (concat)                       |                             |   V                      #
+ *  +---------------+   #    o---------o             (xor)+---------+      o---------o      | o----o     o---------o   #    +--------------+
+ *  | entropy Block | -----> | sha-256 | --(offset)-<     | rndCore | ---> | sha-256 | --+--+-| +1 |---> | sha-256 | -----> | random Block |
+ *  +---------------+   #    o---------o             (xor)+---------+      o---------o   |    o----o     o---------o   #    +--------------+
+ *                      #                                 (xor) (xor)                    |                             #
+ *                      #                                   ^     ^                      |                             #
+ *                      #                                    \   /                       |                             #
+ *                      #                                   (offset)---------------------+                             #
+ *                      #                                                                                              #
+ *                      ################################################################################################
+ * \endverbatim
+ */
+
+ /* \verbatim
+ *                      ################################################################################################
+ *                      #                                                                                              #
+ *                      #         +---------------------------+                                                        #
+ *                      #         |                           |                             +---+                      #
+ *                      #         V                           |                             |   |                      #
+ *                      #      (concat)                       |                             |   V                      #
+ *  +---------------+   #    o---------o             (xor)+---------+      o---------o      | o----o     o---------o   #    +--------------+
+ *  | entropy Block | -----> | sha-256 | --(offset)-<     | rndCore | ---> | sha-256 | --+--+-| +1 |---> | sha-256 | -----> | random Block |
+ *  +---------------+   #    o---------o             (xor)+---------+      o---------o   |    o----o     o---------o   #    +--------------+
+ *                      #                                 (xor) (xor)                    |                             #
+ *                      #                                   ^     ^                      |                             #
+ *                      #                                    \   /                       |                             #
+ *                      #                                   (offset)---------------------+                             #
+ *                      #                                                                                              #
+ *                      ################################################################################################
+ * \endverbatim
+ */
+
+#include <stdint.h>
+#include <string.h>
+#include "sha256.h"
+#include "entropium.h"
+
+/**
+ * \brief secret entropy pool. 
+ * This is the core of the random which is generated
+ */
+uint32_t rndCore[16]; 
+
+/*************************************************************************/
+
+/**
+ * \brief This function adds entropy to the central entropy pool
+ * 
+ * @param length This ist the length of the random data in BITS. 
+ * @param data This is the random data which should be added to the entropy pool
+*/
+/* idea is: hash the message and add it via xor to rndCore
+ *
+ * length in bits 
+ * 
+ * we simply first "hash" rndCore, then entropy.
+ */
+void entropium_addEntropy(unsigned length_b, const void* data){
+       sha256_ctx_t s;
+       static uint8_t offset=0; /* selects if higher or lower half gets updated */
+       sha256_init(&s);
+       sha256_nextBlock(&s, rndCore);
+       while (length_b>=512){
+               sha256_nextBlock(&s, data);
+               data = (uint8_t*)data+ 512/8;
+               length_b -= 512;        
+       }
+       sha256_lastBlock(&s, data, length_b);
+       uint8_t i;
+       for (i=0; i<8; ++i){
+               rndCore[i+offset] ^= s.h[i];
+       }
+       offset ^= 8; /* hehe */
+}
+
+/*************************************************************************/
+/**
+ * \brief This function fills a given buffer with 32 random bytes
+ * @param b Pointer to buffer wich is to fill
+ */
+void entropium_getRandomBlock(void *b){
+       sha256_ctx_t s;
+       uint8_t offset=8;
+       
+       sha256_init(&s);
+       sha256_lastBlock(&s, rndCore, 512); /* remeber the byte order! */
+       uint8_t i;
+       for (i=0; i<8; ++i){
+               rndCore[i+offset] ^= s.h[i];
+       }
+       offset ^= 8; /* hehe */
+       memcpy(b, s.h, 32); /* back up first hash in b */
+       ((uint8_t*)b)[*((uint8_t*)b)&31]++;     /* the important increment step */
+       sha256_init(&s);
+       sha256_lastBlock(&s, b, 256);
+       memcpy(b, s.h, 32);
+}
+
+/*************************************************************************/
+ 
+/**
+ * \brief This function simply returns a random byte
+ * @return a random byte
+ */
+uint8_t entropium_getRandomByte(void){
+       static uint8_t block[32];
+       static uint8_t i=32;
+       
+       if (i==32){
+               entropium_getRandomBlock((void*)block);
+               i=0;
+       }       
+       return block[i++];
+}
+
+/*************************************************************************/
+ 
+/**
+ * \brief This function fills the given bock with length random bytes
+ * @return a random byte
+ */
+ 
+void entropium_fillBlockRandom(void* block, unsigned length_B){
+       while(length_B>ENTROPIUM_RANDOMBLOCK_SIZE){
+               entropium_getRandomBlock(block);
+               block = (uint8_t*)block + ENTROPIUM_RANDOMBLOCK_SIZE;
+               length_B -= ENTROPIUM_RANDOMBLOCK_SIZE;
+       }
+       while(length_B){
+               *((uint8_t*)block) = entropium_getRandomByte();
+               block= (uint8_t*)block +1; --length_B;
+       }
+}
+ 
+