kernel - Update random number generator

* Update the random number generator with recommended changes to IBAA.
  This addresses a short-cycle problem and prevents bad initial states.

* Passes diehard (as did the original).

* Note that DragonFly continuously injects entropy and was likely not
  subject to these issues, and with these changes is even less so.

Submitted-by: Robin Carey <robin.carey1@googlemail.com>

diff --git a/sys/kern/kern_nrandom.c b/sys/kern/kern_nrandom.c
index 9c0cfd3..60205a4 100644 (file)
--- a/sys/kern/kern_nrandom.c
+++ b/sys/kern/kern_nrandom.c
@@ -171,19 +171,22 @@ typedef   u_int32_t       u4;   /* unsigned four bytes, 32 bits */
 #define        SIZE            (1 << ALPHA)
 #define MASK           (SIZE - 1)
 #define        ind(x)          ((x) & (SIZE - 1))
-#define        barrel(a)       (((a) << 19) ^ ((a) >> 13))  /* beta=32,shift=19 */
+#define        barrel(a)       (((a) << 20) ^ ((a) >> 12))  /* beta=32,shift=20 */
  
 static void IBAA
 (
        u4 *m,          /* Memory: array of SIZE ALPHA-bit terms */
        u4 *r,          /* Results: the sequence, same size as m */
        u4 *aa,         /* Accumulator: a single value */
-       u4 *bb          /* the previous result */
+       u4 *bb,         /* the previous result */
+       u4 *counter     /* counter */
 )
 {
        u4 a, b, x, y, i;
  
-       a = *aa; b = *bb;
+       a = *aa;
+       b = *bb + *counter;
+       ++*counter;
        for (i = 0; i < SIZE; ++i) {
                x = m[i];  
                a = barrel(a) + m[ind(i + (SIZE / 2))]; /* set a */
@@ -200,6 +203,7 @@ static u4   IBAA_memory[SIZE];
 static u4      IBAA_results[SIZE];
 static u4      IBAA_aa;
 static u4      IBAA_bb;
+static u4      IBAA_counter;
 
 static volatile int IBAA_byte_index;
 
@@ -221,6 +225,7 @@ IBAA_Init(void)
                IBAA_memory[i] = i;
        }
        IBAA_aa = IBAA_bb = 0;
+       IBAA_counter = 0;
        IBAA_byte_index = sizeof(IBAA_results); /* force IBAA_Call() */
 }
 
@@ -230,7 +235,7 @@ IBAA_Init(void)
 static void
 IBAA_Call (void)
 {
-       IBAA(IBAA_memory, IBAA_results, &IBAA_aa, &IBAA_bb);
+       IBAA(IBAA_memory, IBAA_results, &IBAA_aa, &IBAA_bb, &IBAA_counter);
        IBAA_byte_index = 0;
 }