Allow for higher granularity of entropy estimates by using 'double'

[openssl.git] / crypto / rand / md_rand.c

diff --git a/crypto/rand/md_rand.c b/crypto/rand/md_rand.c
index d6f47b6e9d7b879afc6f64fff70446adfeedb2c0..34843d04dbe32c39432edd2c4f8a79af5df57e5e 100644 (file)
--- a/crypto/rand/md_rand.c
+++ b/crypto/rand/md_rand.c
@@ -56,7 +56,7 @@
  * [including the GNU Public Licence.]
  */
 
-#define ENTROPY_NEEDED 32  /* require 128 bits of randomness */
+#define ENTROPY_NEEDED 16  /* require 128 bits = 16 bytes of randomness */
 
 #ifndef MD_RAND_DEBUG
 # ifndef NDEBUG
@@ -138,13 +138,13 @@ static int state_num=0,state_index=0;
 static unsigned char state[STATE_SIZE+MD_DIGEST_LENGTH];
 static unsigned char md[MD_DIGEST_LENGTH];
 static long md_count[2]={0,0};
-static unsigned entropy=0;
+static double entropy=0;
 
 const char *RAND_version="RAND" OPENSSL_VERSION_PTEXT;
 
 static void ssleay_rand_cleanup(void);
 static void ssleay_rand_seed(const void *buf, int num);
-static void ssleay_rand_add(const void *buf, int num, int add_entropy);
+static void ssleay_rand_add(const void *buf, int num, double add_entropy);
 static int ssleay_rand_bytes(unsigned char *buf, int num);
 static int ssleay_rand_pseudo_bytes(unsigned char *buf, int num);
 
@@ -172,7 +172,7 @@ static void ssleay_rand_cleanup(void)
        entropy=0;
        }
 
-static void ssleay_rand_add(const void *buf, int num, int add)
+static void ssleay_rand_add(const void *buf, int num, double add)
        {
        int i,j,k,st_idx;
        long md_c[2];
@@ -186,9 +186,9 @@ static void ssleay_rand_add(const void *buf, int num, int add)
        /*
         * (Based on the rand(3) manpage)
         *
-        * The input is chopped up into units of 16 bytes (or less for
+        * The input is chopped up into units of 20 bytes (or less for
         * the last block).  Each of these blocks is run through the hash
-        * function as follow:  The data passed to the hash function
+        * function as follows:  The data passed to the hash function
         * is the current 'md', the same number of bytes from the 'state'
         * (the location determined by in incremented looping index) as
         * the current 'block', the new key data 'block', and 'count'
@@ -286,7 +286,7 @@ static void ssleay_rand_add(const void *buf, int num, int add)
 #ifndef THREADS        
        assert(md_c[1] == md_count[1]);
 #endif
-       if (entropy < ENTROPY_NEEDED)
+       if (entropy < ENTROPY_NEEDED) /* stop counting when we have enough */
            entropy += add;
        }
 
@@ -324,13 +324,15 @@ static int ssleay_rand_bytes(unsigned char *buf, int num)
        /*
         * (Based on the rand(3) manpage:)
         *
-        * For each group of 8 bytes (or less), we do the following:
+        * For each group of 10 bytes (or less), we do the following:
         *
-        * Input into the hash function the top 8 bytes from 'md', the bytes
-        * that are to be overwritten by the random bytes, and bytes from the
+        * Input into the hash function the top 10 bytes from the
+        * local 'md' (which is initialized from the global 'md'
+        * before any bytes are generated), the bytes that are
+        * to be overwritten by the random bytes, and bytes from the
         * 'state' (incrementing looping index).  From this digest output
-        * (which is kept in 'md'), the top (upto) 8 bytes are
-        * returned to the caller and the bottom (upto) 8 bytes are xored
+        * (which is kept in 'md'), the top (up to) 10 bytes are
+        * returned to the caller and the bottom (up to) 10 bytes are xored
         * into the 'state'.
         * Finally, after we have finished 'num' random bytes for the
         * caller, 'count' (which is incremented) and the local and global 'md'
@@ -495,12 +497,12 @@ static int ssleay_rand_pseudo_bytes(unsigned char *buf, int num)
  */
 /*
  * I have modified the loading of bytes via RAND_seed() mechanism since
- * the origional would have been very very CPU intensive since RAND_seed()
+ * the original would have been very very CPU intensive since RAND_seed()
  * does an MD5 per 16 bytes of input.  The cost to digest 16 bytes is the same
  * as that to digest 56 bytes.  So under the old system, a screen of
- * 1024*768*256 would have been CPU cost of approximatly 49,000 56 byte MD5
+ * 1024*768*256 would have been CPU cost of approximately 49,000 56 byte MD5
  * digests or digesting 2.7 mbytes.  What I have put in place would
- * be 48 16k MD5 digests, or efectivly 48*16+48 MD5 bytes or 816 kbytes
+ * be 48 16k MD5 digests, or effectively 48*16+48 MD5 bytes or 816 kbytes
  * or about 3.5 times as much.
  * - eric 
  */