[vvgaczoc] 5GB Scrypt

Scrypt at suggested parameters "for a sensitive file" (N, r, p) = (2^20, 8, 1) consumes 1 GiB of memory, and memory use can be increased linearly by increasing N or r.

Does anything abruptly interesting happen when the memory requirement exceeds 4 GiB, the maximum for 32-bit addressing?  The first thought is this: For normal users on general purpose computers, all 64-bit machines, they won't notice any abrupt change.  However, for ASIC and other specialized crackers, a fully 32-bit infrastructure will no longer be sufficient: they will have to move to 64-bit memory addressing, doubling the cost of at least one (possibly small) part of their hardware.

On the other hand, so long as one is designing ASIC, using 33-bit addressing might not be that hard (not cost especially much more area than 32-bit), and in fact, 33 bits gives more advantage to ASIC over CPUs who are forced to process 33-bit numbers as 64 bits.

But perhaps better is automatically scaled difficulty as in Vertcoin.