A short Arduino Due sketch that measures the time it takes the Due's ARM processor's true random number generator to produce 1Mb of entropy.

due_hwrng_speed_test.ino

// due_hwrng_speed_test.ino
//  by Walter Anderson
//  April 5, 2014
//
//  This is a speed test run on an Arduino Due with an ATSAM3X8E-AU chip dated 1317, it produced the following
//  output:
//     Starting time test for speed of generation of hardware randrom number gebnrator.
//     It took 262 milliseconds to generato 1,048,576 bytes of entropy!
//  This equates to 4,002,198 bytes per second!
//
#include <sam.h>
#include <sam3xa/include/component/component_trng.h>

uint32_t test_hwrng()
{
    static bool enabled = false;
    if (!enabled) {
        pmc_enable_periph_clk(ID_TRNG);
        TRNG->TRNG_IDR = 0xFFFFFFFF;
        TRNG->TRNG_CR = TRNG_CR_KEY(0x524e47) | TRNG_CR_ENABLE;
        enabled = true;
    }

    while (! (TRNG->TRNG_ISR & TRNG_ISR_DATRDY))
        ;
    return TRNG->TRNG_ODATA;
}

void setup() {
  unsigned long start_time;
  unsigned long end_time;
  unsigned long elapsed_time;
  
  Serial.begin(9600);  // I use 9600 baud to maintain consistency for my Entropy library testing procedures
  Serial.println("Starting time test for speed of generation of hardware randrom number gebnrator.");
  start_time = millis();
  for (long i = 0; i < 262144; i++) 
  {
    elapsed_time = test_hwrng();  // just reusing a 32-but variable
  }
  end_time = millis();
  elapsed_time = end_time - start_time;
  Serial.print("It took ");
  Serial.print(elapsed_time);
  Serial.println(" milliseconds to generato 1,048,576 bytes of entropy!");
}

void loop() {
}