Method for computing a probabilistic encryption scheme for encrypting a data item in an electronic device comprising the steps of: a) computing a plurality of random bit strings i r 1 , ..., r m , m being the number of random bit strings, in a computation cluster; and processing the plurality of random bit strings with a randomness preparation function f in the computation cluster to obtain a plurality of processed random bit strings f(r 1 ), ..., f(r m ); b) sending, by the computation cluster, the processed plurality of random bit strings (f(r 1 ), ..., f(r m )) to the electronic device; c) generating, by the electronic device, a random string r E for using in the probabilistic encryption scheme in the electronic device using a subset of the plurality of the random bit strings computed in the computation cluster; and d) encrypting the data item using the random string r E generated in the electronic device; and wherein generating the random string r E consists in recombining of the subset of the plurality of processed random bit strings using a recombination function c; and wherein the generation of the random string r E for using in the encryption scheme in the electronic device is performed using the following function: r E = c f r 1 , ... , f r m , r , and r being a random bit string generated in the electronic device of length q•log 2 (m) with q being a predefined parameter; and wherein the probabilistic encryption scheme is defined as follows: E d , g n , R = g d · R n mod n 2 , with d being the data item, the pair (g,n) being the key, R being the random string for using in the encryption scheme, g is a generator and n is the size of the plain text space; and wherein the function f is based on modular exponentiation and defined as f(r)=r n (mod n 2 ); and c(f(r 1 ),...,f(r m ),r) is defined so as to split the random bit string r into q pieces of length log 2 (m) which corresponds to q indices into the list of the m processed random bit strings f(r 1 ),...,f(r m ) and to multiply the corresponding q processed random bit strings, thereby obtaining the random string r E . a) computing a plurality of random bit strings i r 1 , ..., r m , m being the number of random bit strings, in a computation cluster; and processing the plurality of random bit strings with a randomness preparation function f in the computation cluster to obtain a plurality of processed random bit strings f(r 1 ), ..., f(r m ); b) sending, by the computation cluster, the processed plurality of random bit strings (f(r 1 ), ..., f(r m )) to the electronic device; c) generating, by the electronic device, a random string r E for using in the probabilistic encryption scheme in the electronic device using a subset of the plurality of the random bit strings computed in the computation cluster; and d) encrypting the data item using the random string r E generated in the electronic device; and wherein generating the random string r E consists in recombining of the subset of the plurality of processed random bit strings using a recombination function c; and wherein the generation of the random string r E for using in the encryption scheme in the electronic device is performed using the following function: r E = c f r 1 , ... , f r m , r , and r being a random bit string generated in the electronic device of length q•log 2 (m) with q being a predefined parameter; <EOS>