[kpnexrdr] Provably secure symmetric ciphers

I think I have heard of symmetric cryptographic primitives (symmetric ciphers and hashes) whose strength is provably as strong as integer factorization or discrete logarithm.  They are supposedly generally not used because they are too slow.

How slow is too slow?  I think such methods should be used more often.  For encrypting email, I think 30 seconds of computing is acceptable, especially relative to the amount of time it took to write the email.  At least, give the user the choice of how long he or she is willing to wait.

What are the names of these ciphers, assuming they have already been invented?  Blum Blum Shub probably can be a stream cipher. Provably secure cryptographic hash functions. Their use has not been standardized, as far as I know. It would be nice if they were drop-in replacements for things like AES or SHA2.

However, large computations are more vulnerable to side channel attacks.