62 lines
1.3 KiB
C
62 lines
1.3 KiB
C
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#include <Arduino.h>
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static bool
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hydro_random_rbit(uint16_t x)
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{
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uint8_t x8;
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x8 = ((uint8_t) (x >> 8)) ^ (uint8_t) x;
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x8 = (x8 >> 4) ^ (x8 & 0xf);
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x8 = (x8 >> 2) ^ (x8 & 0x3);
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x8 = (x8 >> 1) ^ x8;
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return (bool) (x8 & 1);
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}
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static int
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hydro_random_init(void)
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{
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const char ctx[hydro_hash_CONTEXTBYTES] = { 'h', 'y', 'd', 'r', 'o', 'P', 'R', 'G' };
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hydro_hash_state st;
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uint16_t ebits = 0;
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uint16_t tc;
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bool a, b;
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cli();
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MCUSR = 0;
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WDTCSR |= _BV(WDCE) | _BV(WDE);
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WDTCSR = _BV(WDIE);
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sei();
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hydro_hash_init(&st, ctx, NULL);
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while (ebits < 256) {
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delay(1);
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tc = TCNT1;
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hydro_hash_update(&st, (const uint8_t *) &tc, sizeof tc);
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a = hydro_random_rbit(tc);
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delay(1);
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tc = TCNT1;
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b = hydro_random_rbit(tc);
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hydro_hash_update(&st, (const uint8_t *) &tc, sizeof tc);
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if (a == b) {
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continue;
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}
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hydro_hash_update(&st, (const uint8_t *) &b, sizeof b);
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ebits++;
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}
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cli();
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MCUSR = 0;
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WDTCSR |= _BV(WDCE) | _BV(WDE);
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WDTCSR = 0;
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sei();
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hydro_hash_final(&st, hydro_random_context.state, sizeof hydro_random_context.state);
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hydro_random_context.counter = ~LOAD64_LE(hydro_random_context.state);
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return 0;
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}
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ISR(WDT_vect) { }
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