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samd/moduos: Add uos.urandom() using the phase-jitter rng. 

This RNG passes many of the Diehard tests and also the AIS31 test suite.
The RNG is quite slow, delivering 200bytes/s.

Tested on boards with and without a crystal.
This commit is contained in:
robert-hh 2023-02-14 10:02:22 +01:00 committed by Damien George
parent 4160ec087b
commit b110266897
3 changed files with 22 additions and 12 deletions
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5
ports/samd/mcu/samd21/mpconfigmcu.h
View File

@ -22,8 +22,8 @@
#define MICROPY_PY_CMATH (0)
#endif
#define MICROPY_PY_URANDOM_SEED_INIT_FUNC (trng_random_u32())
unsigned long trng_random_u32(void);
#define MICROPY_PY_URANDOM_SEED_INIT_FUNC (trng_random_u32(300))
unsigned long trng_random_u32(int delay);
#define VFS_BLOCK_SIZE_BYTES (1536) // 24x 64B flash pages;
@ -36,6 +36,7 @@ unsigned long trng_random_u32(void);
#define MICROPY_PY_MACHINE_RTC (1)
#endif
#endif
#define MICROPY_PY_UOS_URANDOM (1)
#ifndef MICROPY_PY_MACHINE_PIN_BOARD_CPU
#define MICROPY_PY_MACHINE_PIN_BOARD_CPU (1)

20
ports/samd/moduos.c
View File

@ -52,6 +52,23 @@ uint32_t trng_random_u32(void) {
return REG_TRNG_DATA;
}
#define TRNG_RANDOM_U32 trng_random_u32()
#endif // defined(MCU_SAMD51)
#if defined(MCU_SAMD21)
extern volatile uint32_t rng_state;
uint32_t trng_random_u32(int delay) {
mp_hal_delay_ms(delay); // wait a few cycles
uint32_t upper = rng_state;
mp_hal_delay_ms(delay); // wait again a few cycles
return (upper & 0xffff0000) | (rng_state >> 16);
}
#define trng_start()
#define TRNG_RANDOM_U32 trng_random_u32(10)
#endif
#if MICROPY_PY_UOS_URANDOM
STATIC mp_obj_t mp_uos_urandom(mp_obj_t num) {
mp_int_t n = mp_obj_get_int(num);
@ -62,7 +79,7 @@ STATIC mp_obj_t mp_uos_urandom(mp_obj_t num) {
trng_start();
for (int i = 0; i < n; i++) {
if ((i % 4) == 0) {
rngval = trng_random_u32();
rngval = TRNG_RANDOM_U32;
}
vstr.buf[i] = rngval & 0xff;
rngval >>= 8;
@ -72,7 +89,6 @@ STATIC mp_obj_t mp_uos_urandom(mp_obj_t num) {
STATIC MP_DEFINE_CONST_FUN_OBJ_1(mp_uos_urandom_obj, mp_uos_urandom);
#endif // MICROPY_PY_UOS_URANDOM
#endif // defined(MCU_SAMD51)
#if MICROPY_PY_UOS_DUPTERM_BUILTIN_STREAM
bool mp_uos_dupterm_is_builtin_stream(mp_const_obj_t stream) {

9
ports/samd/samd_isr.c
View File

@ -96,7 +96,7 @@ void Default_Handler(void) {
void SysTick_Handler(void) {
#if defined(MCU_SAMD21)
// Use the phase jitter between the clocks to get some entropy
// and accumulate the random number register.
// and accumulate the random number register with a "spiced" LCG.
rng_state = (rng_state * 32310901 + 1) ^ (REG_TC4_COUNT32_COUNT >> 1);
#endif
@ -108,13 +108,6 @@ void SysTick_Handler(void) {
}
}
#if defined(MCU_SAMD21)
uint32_t trng_random_u32(void) {
mp_hal_delay_ms(320); // wait for ten cycles of the rng_seed register
return rng_state;
}
#endif
void us_timer_IRQ(void) {
#if defined(MCU_SAMD21)
if (TC4->COUNT32.INTFLAG.reg & TC_INTFLAG_OVF) {