A key generation device (100) configured to generate a public key (126) for use in a public key encryption device and a corresponding private key (114) for use in a private key decryption device, the key generation device comprising a private key generator (110) configured for obtaining in electronic form a private random value (112, s), and generating the private key (114), the private key comprising the private random value (112), and a public key generator (120) configured for obtaining in electronic form a public set of bivariate polynomials (122, fi (,)), computing a public univariate polynomial (124) by summing over univariate polynomials obtained by substituting the private random value (112, s) into the polynomials of the public set (122, fi (s,)), and generating the public key (126), the public key comprising the public univariate polynomial (124) and the public set (122).