(1) The point is, if you're considering "average length 8 character passwords", there's a temptation to assume you're working with 2^56 bits of entropy. In reality, you're getting nothing even close to that; only a tiny minority of users use truly random passwords. If you're not using random passwords, the speed of your hash starts to matter a lot.
(2) Sorry. I meant to sound emphatic, not nasty.
(3) These are all hashing schemes; I'm arguing against using blazingly-fast hashing for password storage. If you're stuck with SHA, Colin's right; use a "stretched" version that iterates several thousand times (just re-hash the hash in a loop), and use a 32 bit nonce (err salt), generated on the fly for each user every time their password is changed, stored in an integer column in the user table.
Comments
(1) The point is, if you're considering "average length 8 character passwords", there's a temptation to assume you're working with 2^56 bits of entropy. In reality, you're getting nothing even close to that; only a tiny minority of users use truly random passwords. If you're not using random passwords, the speed of your hash starts to matter a lot.
(2) Sorry. I meant to sound emphatic, not nasty.
(3) These are all hashing schemes; I'm arguing against using blazingly-fast hashing for password storage. If you're stuck with SHA, Colin's right; use a "stretched" version that iterates several thousand times (just re-hash the hash in a loop), and use a 32 bit nonce (err salt), generated on the fly for each user every time their password is changed, stored in an integer column in the user table.