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

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

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