One embodiment of the invention includes a method, including performing, a symmetric homomorphic encryption of a secret SA with a cryptographic key H as input yielding a homomorphic encryption result SA*, sending SA* for mathematical combination by at least one device with at least one secret SB yielding G*, the device A not having access to SB, the at least one device not having access to SA and not having access to H, receiving G*, performing a symmetric homomorphic decryption of data based on G* with H as input yielding a first decrypted output, determining a symmetric cryptographic key KA based on the first decrypted output for secure communication with a first device which is operationally connected to, or includes, a tamper resistant security system including SA and SB therein, securing data using KA yielding secured data, and sending the secured data to the first device.