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stm32/rng: Use Yasmarang for rng_get() if MCU doesn't have HW RNG.

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Damien George 2018-05-22 10:27:21 +10:00
parent cda964198a
commit f68e722005
1 changed files with 26 additions and 0 deletions
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26
ports/stm32/rng.c
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@ -60,4 +60,30 @@ STATIC mp_obj_t pyb_rng_get(void) {
} }
MP_DEFINE_CONST_FUN_OBJ_0(pyb_rng_get_obj, pyb_rng_get); MP_DEFINE_CONST_FUN_OBJ_0(pyb_rng_get_obj, pyb_rng_get);
#else // MICROPY_HW_ENABLE_RNG
// For MCUs that don't have an RNG we still need to provide a rng_get() function,
// eg for lwIP. A pseudo-RNG is not really ideal but we go with it for now. We
// don't want to use urandom's pRNG because then the user won't see a reproducible
// random stream.
// Yasmarang random number generator by Ilya Levin
// http://www.literatecode.com/yasmarang
STATIC uint32_t pyb_rng_yasmarang(void) {
static uint32_t pad = 0xeda4baba, n = 69, d = 233;
static uint8_t dat = 0;
pad += dat + d * n;
pad = (pad << 3) + (pad >> 29);
n = pad | 2;
d ^= (pad << 31) + (pad >> 1);
dat ^= (char)pad ^ (d >> 8) ^ 1;
return pad ^ (d << 5) ^ (pad >> 18) ^ (dat << 1);
}
uint32_t rng_get(void) {
return pyb_rng_yasmarang();
}
#endif // MICROPY_HW_ENABLE_RNG #endif // MICROPY_HW_ENABLE_RNG