Ivan Krstić
Sun, 30 Mar 2008 18:04:50 -0700
On Mar 30, 2008, at 3:12 PM, Leichter, Jerry wrote:
How would that help?
Unless I'm misunderstanding Zooko's writeup, he's worried about an attacker going from a partially-known plaintext (e.g. a form bank letter) to a completely-known plaintext by repeating the following process:
1. take partially known plaintext 2. make a guess, randomly or more intelligently where possible, about the unknown parts 3. take the current integrated partial+guessed plaintext, hash to obtain convergence key 4. verify whether that key exists in the storage index 5. if yes, you've found the full plaintext. if not, repeat from '2'.That's a brute force search. If your convergence key, instead of being a simple file hash, is obtained through a deterministic but computationally expensive function such as PBKDF2 (or the OpenBSD bcrypt, etc), then step 3 makes an exhaustive search prohibitive in most cases while not interfering with normal filesystem operation. What am I missing?
Cheers, -- Ivan Krstić <[EMAIL PROTECTED]> | http://radian.org --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]