Providing security against user collusion in data analytics using random group selection

Methods for secure random selection of t client devices which from a set of N client devices and methods for secure computation of inputs of t client devices which are randomly selected from a set of N client devices are described. Such random selection method may include determining an initial binary vector b of weight t by setting the first t bits to one: bi = 1, 1 ≤ i ≤ t, and all further bits to zero: bi = 0, t < i ≤ N; each client device i (i=1,...,N) of the set of N client devices jointly generating a random binary vector b of weight t in an obfuscated domain on the basis of the initial binary vector b including: determining a position n in the binary vector; determining a random number r in {n,n+1,...N}; and, using the random number to swap binary values at positions n and r of the binary vector b.