], however, scientists have proposed a method using memory-bound functions as a means to discourage spammers from abusing resources, which could be a major breakthrough in that area.
In 1992, IBM research scientists Cynthia Dwork and Moni Naor published a paper at CRYPTO 1992 titled Pricing via Processing or Combatting Junk Mail,[1] suggesting a possibility of using CPU-bound functions to deter abusers from sending spam.
The function G() is selected such that the verification by Recipient is relatively fast (e.g., taking a millisecond) and such that the computation by Sender is somewhat slow (involving at least several seconds).
The disparity in client CPU speed constitutes one of the prominent roadblocks to widespread adoption of any scheme based on a CPU-bound function.
These ratios are "egalitarian" enough for the intended applications: the functions are effective in discouraging abuses and do not add a prohibitive delay on legitimate interactions, across a wide range of systems.
In recent years, the speed of CPU has grown drastically, but there has been comparatively small progress in developing faster main memory.
Since the ratios of memory latencies of machines built in the last five years is typically no greater than two, and almost always less than four, the memory-bound function will be egalitarian to most systems for the foreseeable future.