▁B logs ▁Like ▁e - mail , ▁blog s ▁often ▁fall ▁victim ▁to ▁comment ▁sp am . ▁Some ▁blog ▁own ers ▁have ▁used ▁hash c ash ▁scripts ▁written ▁in ▁the ▁JavaScript ▁language ▁to ▁slow ▁down ▁comment ▁sp amm ers . ▁Some ▁scripts ▁( such ▁as ▁wp - hash c ash ) ▁claim ▁to ▁implement ▁hash c ash ▁but ▁instead ▁depend ▁on ▁JavaScript ▁ob f us cation ▁to ▁force ▁the ▁client ▁to ▁generate ▁a ▁matching ▁key ; ▁while ▁this ▁does ▁require ▁some ▁processing ▁power , ▁it ▁does ▁not ▁use ▁the ▁hash c ash ▁algorithm ▁or ▁hash c ash ▁st amps . ▁ ▁Intel lect ual ▁property ▁Hash c ash ▁is ▁not ▁pat ented , ▁and ▁the ▁reference ▁implementation ▁and ▁most ▁of ▁the ▁other ▁implementations ▁are ▁free ▁software . ▁Hash c ash ▁is ▁included ▁or ▁available ▁for ▁many ▁Linux ▁distributions . ▁ ▁R SA ▁has ▁made ▁IP R ▁statements ▁to ▁the ▁I ET F ▁about ▁client - p uzz les ▁in ▁the ▁context ▁of ▁an ▁R FC ▁that ▁described ▁client - p uzz les ▁( not ▁hash c ash ). ▁The ▁R FC ▁included ▁hash c ash ▁in ▁the ▁title ▁and ▁referenced ▁hash c ash , ▁but ▁the ▁mechanism ▁described ▁in ▁it ▁is ▁a ▁known - sol ution ▁interactive ▁challenge ▁which ▁is ▁more ▁a kin ▁to ▁Client - P uzz les ; ▁hash c ash ▁is ▁non - inter active ▁and ▁therefore ▁does ▁not ▁have ▁a ▁known ▁solution . ▁In ▁any ▁case ▁R SA ' s ▁IP R ▁statement ▁can ▁not ▁apply ▁to ▁hash c