Robert J. Bradbury wrote :
>> As for RC5, THAT is a complete waste of time. We
>> already all agree on what currently makes for a "secure"
>> level of encryption.
>
>At least until they get an operational quantum computer
>(which is probably 20 years out if it is even doable).
>
>Question: Does anyone know if there is an encryption
>methodology that will work if QC cracks the factoring problem?
Cracking the factoring problem will only render *public* key encryption methods based on factoring obsolete. There are public key encryption methods based on other one way calculations, (like the discrete logarithm), but I dont know about their resistance to quantum computations.
As far as i know conventional secret key hash encryption methods cannot be "cracked" by quantum computations.