bitcoin_attack_success_probability.c

#include <math.h>
#include <stdio.h>

double attackerSuccessProbability(double q, int z) {
    double p = 1.0 - q;
    double lambda = z * (q / p);
    double sum = 1.0;
    int i, k;
    for (k = 0; k <= z; k++) {
        double poisson = exp(-lambda);
        for (i = 1; i <= k; i++)
            poisson *= lambda / i;
        sum -= poisson * (1 - pow(q / p, z - k));
    }
    return sum;
}

int main() {
    for (int i = 0; i < 10; i++) {
        printf("z=%d, p=%f\n", i, attackerSuccessProbability(0.51, i));
    }
    return 0;
}