[cookiecaper]

I'd expect random swirls to be reliable, or any obfuscation that introduces a reasonable amount of entropy. This whole attack relies on an almost-exact replication of the original blurred image. If you do something a computer can't easily reproduce over and over again, or something that looks the same no matter what the obfuscated content is (like blacking out), this attack cannot work.

[Robin_Message]

Actually swirls are very reversible - http://news.bbc.co.uk/1/hi/7384834.stm (Paedophile caught from video with swirled obfuscation of his face.)

You're definitely right about adding entropy though, but why bother? Just blacking it out guarantees how much information is available - zero.

[McP]

That's not a random swirl. Interesting though