Obfuscating the key would only work so long as nobody figures out how it was obfuscated. I don't know but would expect that File Vault already does. As for pseudo-random memory addresses, I don't think that would help much either since checking all of the addressable memory space is a much easier problem to solve than a brute force attack. This attack on the encryption key isn't a new one. All that's new is the attention to the Mac.
2/1/12 at 6:25pm