Quantum computers might be able to pwn a 128 bit symmetric algorithm with grovers algorithm, but they will have no luck with 256 bit symmetric algorithms. They are primarily for breaking asymmetric algorithms. If the asymmetric algorithm used for symmetric key transfer is broken, they don't need to break the symmetric algorithm because they can get the key to decrypt the ciphertext by pwning the asymmetric algorithm. False, it will halve the strength of symmetric ciphers with grovers algorithm, with enough stabilized qubits shors algorithm can obtain private asymmetric keys from public asymmetric keys almost instantaneously. Of course that is only against weak asymmetric algorithms, but that includes RSA and ECDH/ECDSA. Quantum computers are currently predicted to start becoming exponentially more powerful, and an RSA key with 128 bit symmetric security against a quantum computer will take ~two terabyte hard drives to store. Slightly less for ECC but still enormous. The future of asymmetric encryption is probably in multivariate quadratic polynomial based algorithms. That confuses a side channel attack with a bypass attack. You have that backwards.