Friday, February 10, 2012

[mevznrcq] Hashcash and GPUs

A potential problem with Hashcash is that "stamps" can be generated by special purpose hardware (GPU, FPGA, ASIC) much faster than regular computers (as evidenced by Bitcoin).  Similarly, specialized spammers could generate messages seemingly generated with (say) 1 second of CPU time whose Hashcash actually took much less time to generate on specialized hardware.

An Scrypt-like hash function (requiring a lot of memory) might somewhat thwart that, though very specialized hardware attacks might still be possible.

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