Diff: random/random.c

Revision:

64:d1b9e47aa754

diff -r 28738aaad2a8 -r d1b9e47aa754 random/random.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/random/random.c	Fri Apr 12 13:03:45 2019 +0000
@@ -0,0 +1,26 @@
+#include <stdint.h>
+
+#include "hrtimer.h"
+#include "random.h"
+
+/*
+Uses the low 8 bits of the hrtimer to give the number of cycles per scan.
+The cycles per scan depends on many factors including network activity.
+Network activity has a high entropy as it depends on many machines and human activity.
+The minimum scan is typically at least 5000 so taking the low 8 bits should be indeterminate.
+*/
+
+uint8_t RandomBytes[RANDOM_LENGTH];
+
+void RandomMain()
+{
+    //Establish the scan time
+    static uint32_t scanTimer = 0;
+    uint32_t elapsed = HrTimerSinceRepetitive(&scanTimer);
+    
+    //Make the random number using the low 8 bits of the scan time as entropy
+    static int position = 0;
+    RandomBytes[position] ^= elapsed & 0xFF;
+    position++;
+    if (position >= RANDOM_LENGTH) position  = 0;
+}
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