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Date: Tue, 21 Jan 2014 06:19:23 +0400 From: Solar Designer <solar@...nwall.com> To: discussions@...sword-hashing.net Subject: Re: [PHC] Modified pseudo-random distribution in NoelKDF On Mon, Jan 20, 2014 at 03:56:13PM -0500, Bill Cox wrote: > On Mon, Jan 20, 2014 at 9:01 AM, Solar Designer <solar@...nwall.com> wrote: > > Do you have specific numbers for the original approach above, and what > > would be high enough (in your opinion)? > > I would like to hurt a guy using only 1/4 of the memory enough that > his attack is not practical. I also want to not spend much time in > the second loop forcing an attacker to show memory locations, so I'd > like to read only 1% of the blocks. A guy using only 1/8th should be > deep into impractical TMTO territory. How do you implement thread-level parallelism, or is this scheme with the second loop at 1% only suitable for p=1? > The average recalculation for 10,000,000 nodes covered by evenly > spaced pebbles [...] What if they are not evenly spaced? You're making the distribution of lookup indices highly non-uniform, so perhaps an attacker with limited memory can adjust the spacing accordingly and achieve a lower TMTO penalty? Alexander
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