A QUBO solving method for optimizing a function f(x) defined by a matrix Q and a vector p such 5 that and comprising the steps of: encrypting the function f(x) to be optimized by using an encryption matrix P and/or an encryption vector k; sending the encrypted version of the function to be optimized f′(x′) to a QUBO solver; receiving an encrypted version of the solution to the QUBO problem x′*, obtained by optimization of the encrypted version of the function f′(x′) performed by the QUBO solver; and decrypting the solution to the QUBO problem, thus obtaining x*.