--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/prngs/fortuna.c	Wed Mar 08 12:58:00 2006 +0000
@@ -0,0 +1,390 @@
+/* LibTomCrypt, modular cryptographic library -- Tom St Denis
+ *
+ * LibTomCrypt is a library that provides various cryptographic
+ * algorithms in a highly modular and flexible manner.
+ *
+ * The library is free for all purposes without any express
+ * guarantee it works.
+ *
+ * Tom St Denis, [email protected], http://libtomcrypt.org
+ */
+#include "tomcrypt.h"
+
+/**
+  @file fortuna.c
+  Fortuna PRNG, Tom St Denis
+*/
+  
+/* Implementation of Fortuna by Tom St Denis 
+
+We deviate slightly here for reasons of simplicity [and to fit in the API].  First all "sources"
+in the AddEntropy function are fixed to 0.  Second since no reliable timer is provided 
+we reseed automatically when len(pool0) >= 64 or every FORTUNA_WD calls to the read function */
+
+#ifdef FORTUNA 
+
+/* requries SHA256 and AES  */
+#if !(defined(RIJNDAEL) && defined(SHA256))
+   #error FORTUNA requires SHA256 and RIJNDAEL (AES)
+#endif
+
+#ifndef FORTUNA_POOLS
+   #warning FORTUNA_POOLS was not previously defined (old headers?)
+   #define FORTUNA_POOLS 32
+#endif
+
+#if FORTUNA_POOLS < 4 || FORTUNA_POOLS > 32
+   #error FORTUNA_POOLS must be in [4..32]
+#endif
+
+const struct ltc_prng_descriptor fortuna_desc = {
+    "fortuna", 1024,
+    &fortuna_start,
+    &fortuna_add_entropy,
+    &fortuna_ready,
+    &fortuna_read,
+    &fortuna_done,
+    &fortuna_export,
+    &fortuna_import,
+    &fortuna_test
+};
+
+/* update the IV */
+static void fortuna_update_iv(prng_state *prng)
+{
+   int            x;
+   unsigned char *IV;
+   /* update IV */
+   IV = prng->fortuna.IV;
+   for (x = 0; x < 16; x++) {
+      IV[x] = (IV[x] + 1) & 255;
+      if (IV[x] != 0) break;
+   }
+}
+
+/* reseed the PRNG */
+static int fortuna_reseed(prng_state *prng)
+{
+   unsigned char tmp[MAXBLOCKSIZE];
+   hash_state    md;
+   int           err, x;
+
+   ++prng->fortuna.reset_cnt;
+
+   /* new K == SHA256(K || s) where s == SHA256(P0) || SHA256(P1) ... */
+   sha256_init(&md);
+   if ((err = sha256_process(&md, prng->fortuna.K, 32)) != CRYPT_OK) {
+      return err;
+   }
+
+   for (x = 0; x < FORTUNA_POOLS; x++) {
+       if (x == 0 || ((prng->fortuna.reset_cnt >> (x-1)) & 1) == 0) { 
+          /* terminate this hash */
+          if ((err = sha256_done(&prng->fortuna.pool[x], tmp)) != CRYPT_OK) {
+             return err; 
+          }
+          /* add it to the string */
+          if ((err = sha256_process(&md, tmp, 32)) != CRYPT_OK) {
+             return err;
+          }
+          /* reset this pool */
+          sha256_init(&prng->fortuna.pool[x]);
+       } else {
+          break;
+       }
+   }
+
+   /* finish key */
+   if ((err = sha256_done(&md, prng->fortuna.K)) != CRYPT_OK) {
+      return err; 
+   }
+   if ((err = rijndael_setup(prng->fortuna.K, 32, 0, &prng->fortuna.skey)) != CRYPT_OK) {
+      return err;
+   }
+   fortuna_update_iv(prng);
+
+   /* reset pool len */
+   prng->fortuna.pool0_len = 0;
+   prng->fortuna.wd        = 0;
+
+
+#ifdef LTC_CLEAN_STACK
+   zeromem(&md, sizeof(md));
+   zeromem(tmp, sizeof(tmp));
+#endif
+
+   return CRYPT_OK;
+}
+
+/**
+  Start the PRNG
+  @param prng     [out] The PRNG state to initialize
+  @return CRYPT_OK if successful
+*/  
+int fortuna_start(prng_state *prng)
+{
+   int err, x;
+
+   LTC_ARGCHK(prng != NULL);
+   
+   /* initialize the pools */
+   for (x = 0; x < FORTUNA_POOLS; x++) {
+       sha256_init(&prng->fortuna.pool[x]);
+   }
+   prng->fortuna.pool_idx = prng->fortuna.pool0_len = prng->fortuna.reset_cnt = 
+   prng->fortuna.wd = 0;
+
+   /* reset bufs */
+   zeromem(prng->fortuna.K, 32);
+   if ((err = rijndael_setup(prng->fortuna.K, 32, 0, &prng->fortuna.skey)) != CRYPT_OK) {
+      return err;
+   }
+   zeromem(prng->fortuna.IV, 16);
+
+   return CRYPT_OK;
+}
+
+/**
+  Add entropy to the PRNG state
+  @param in       The data to add
+  @param inlen    Length of the data to add
+  @param prng     PRNG state to update
+  @return CRYPT_OK if successful
+*/  
+int fortuna_add_entropy(const unsigned char *in, unsigned long inlen, prng_state *prng)
+{
+   unsigned char tmp[2];
+   int           err;
+
+   LTC_ARGCHK(in  != NULL);
+   LTC_ARGCHK(prng != NULL);
+
+   /* ensure inlen <= 32 */
+   if (inlen > 32) {
+      return CRYPT_INVALID_ARG;
+   }
+
+   /* add s || length(in) || in to pool[pool_idx] */
+   tmp[0] = 0;
+   tmp[1] = inlen;
+   if ((err = sha256_process(&prng->fortuna.pool[prng->fortuna.pool_idx], tmp, 2)) != CRYPT_OK) {
+      return err;
+   }
+   if ((err = sha256_process(&prng->fortuna.pool[prng->fortuna.pool_idx], in, inlen)) != CRYPT_OK) {
+      return err;
+   }
+   if (prng->fortuna.pool_idx == 0) {
+      prng->fortuna.pool0_len += inlen;
+   }
+   if (++(prng->fortuna.pool_idx) == FORTUNA_POOLS) {
+      prng->fortuna.pool_idx = 0;
+   }
+
+   return CRYPT_OK;
+}
+
+/**
+  Make the PRNG ready to read from
+  @param prng   The PRNG to make active
+  @return CRYPT_OK if successful
+*/  
+int fortuna_ready(prng_state *prng)
+{
+   return fortuna_reseed(prng);
+}
+
+/**
+  Read from the PRNG
+  @param out      Destination
+  @param outlen   Length of output
+  @param prng     The active PRNG to read from
+  @return Number of octets read
+*/  
+unsigned long fortuna_read(unsigned char *out, unsigned long outlen, prng_state *prng)
+{
+   unsigned char tmp[16];
+   int           err;
+   unsigned long tlen;
+
+   LTC_ARGCHK(out  != NULL);
+   LTC_ARGCHK(prng != NULL);
+
+   /* do we have to reseed? */
+   if (++prng->fortuna.wd == FORTUNA_WD || prng->fortuna.pool0_len >= 64) {
+      if ((err = fortuna_reseed(prng)) != CRYPT_OK) {
+         return 0;
+      }
+   }
+
+   /* now generate the blocks required */
+   tlen = outlen;
+
+   /* handle whole blocks without the extra memcpy */
+   while (outlen >= 16) {
+      /* encrypt the IV and store it */
+      rijndael_ecb_encrypt(prng->fortuna.IV, out, &prng->fortuna.skey);
+      out += 16;
+      outlen -= 16;
+      fortuna_update_iv(prng);
+   }
+
+   /* left over bytes? */
+   if (outlen > 0) {
+      rijndael_ecb_encrypt(prng->fortuna.IV, tmp, &prng->fortuna.skey);
+      XMEMCPY(out, tmp, outlen);
+      fortuna_update_iv(prng);
+   }
+       
+   /* generate new key */
+   rijndael_ecb_encrypt(prng->fortuna.IV, prng->fortuna.K   , &prng->fortuna.skey); fortuna_update_iv(prng);
+   rijndael_ecb_encrypt(prng->fortuna.IV, prng->fortuna.K+16, &prng->fortuna.skey); fortuna_update_iv(prng);
+   if ((err = rijndael_setup(prng->fortuna.K, 32, 0, &prng->fortuna.skey)) != CRYPT_OK) {
+      return 0;
+   }
+
+#ifdef LTC_CLEAN_STACK
+   zeromem(tmp, sizeof(tmp));
+#endif
+   return tlen;
+}   
+
+/**
+  Terminate the PRNG
+  @param prng   The PRNG to terminate
+  @return CRYPT_OK if successful
+*/  
+int fortuna_done(prng_state *prng)
+{
+   int           err, x;
+   unsigned char tmp[32];
+
+   LTC_ARGCHK(prng != NULL);
+
+   /* terminate all the hashes */
+   for (x = 0; x < FORTUNA_POOLS; x++) {
+       if ((err = sha256_done(&(prng->fortuna.pool[x]), tmp)) != CRYPT_OK) {
+          return err; 
+       }
+   }
+   /* call cipher done when we invent one ;-) */
+
+#ifdef LTC_CLEAN_STACK
+   zeromem(tmp, sizeof(tmp));
+#endif
+
+   return CRYPT_OK;
+}
+
+/**
+  Export the PRNG state
+  @param out       [out] Destination
+  @param outlen    [in/out] Max size and resulting size of the state
+  @param prng      The PRNG to export
+  @return CRYPT_OK if successful
+*/  
+int fortuna_export(unsigned char *out, unsigned long *outlen, prng_state *prng)
+{
+   int         x, err;
+   hash_state *md;
+
+   LTC_ARGCHK(out    != NULL);
+   LTC_ARGCHK(outlen != NULL);
+   LTC_ARGCHK(prng   != NULL);
+
+   /* we'll write bytes for s&g's */
+   if (*outlen < 32*FORTUNA_POOLS) {
+      return CRYPT_BUFFER_OVERFLOW;
+   }
+
+   md = XMALLOC(sizeof(hash_state));
+   if (md == NULL) {
+      return CRYPT_MEM;
+   }
+
+   /* to emit the state we copy each pool, terminate it then hash it again so 
+    * an attacker who sees the state can't determine the current state of the PRNG 
+    */   
+   for (x = 0; x < FORTUNA_POOLS; x++) {
+      /* copy the PRNG */
+      XMEMCPY(md, &(prng->fortuna.pool[x]), sizeof(*md));
+
+      /* terminate it */
+      if ((err = sha256_done(md, out+x*32)) != CRYPT_OK) {
+         goto LBL_ERR;
+      }
+
+      /* now hash it */
+      if ((err = sha256_init(md)) != CRYPT_OK) {
+         goto LBL_ERR;
+      }
+      if ((err = sha256_process(md, out+x*32, 32)) != CRYPT_OK) {
+         goto LBL_ERR;
+      }
+      if ((err = sha256_done(md, out+x*32)) != CRYPT_OK) {
+         goto LBL_ERR;
+      }
+   }
+   *outlen = 32*FORTUNA_POOLS;
+   err = CRYPT_OK;
+
+LBL_ERR:
+#ifdef LTC_CLEAN_STACK
+   zeromem(md, sizeof(*md));
+#endif
+   XFREE(md);
+   return err;
+}
+ 
+/**
+  Import a PRNG state
+  @param in       The PRNG state
+  @param inlen    Size of the state
+  @param prng     The PRNG to import
+  @return CRYPT_OK if successful
+*/  
+int fortuna_import(const unsigned char *in, unsigned long inlen, prng_state *prng)
+{
+   int err, x;
+
+   LTC_ARGCHK(in   != NULL);
+   LTC_ARGCHK(prng != NULL);
+
+   if (inlen != 32*FORTUNA_POOLS) {
+      return CRYPT_INVALID_ARG;
+   }
+
+   if ((err = fortuna_start(prng)) != CRYPT_OK) {
+      return err;
+   }
+   for (x = 0; x < FORTUNA_POOLS; x++) {
+      if ((err = fortuna_add_entropy(in+x*32, 32, prng)) != CRYPT_OK) {
+         return err;
+      }
+   }
+   return err;
+}
+
+/**
+  PRNG self-test
+  @return CRYPT_OK if successful, CRYPT_NOP if self-testing has been disabled
+*/  
+int fortuna_test(void)
+{
+#ifndef LTC_TEST
+   return CRYPT_NOP;
+#else
+   int err;
+
+   if ((err = sha256_test()) != CRYPT_OK) {
+      return err;
+   }
+   return rijndael_test();
+#endif
+}
+
+#endif
+
+
+/* $Source: /cvs/libtom/libtomcrypt/src/prngs/fortuna.c,v $ */
+/* $Revision: 1.3 $ */
+/* $Date: 2005/05/05 14:35:59 $ */