I understand what CRC is (Cyclic Redundancy Check) and I understand that it can be used on anything (not just files). But my point was, you were asking for a feature and your reasoning behind it was to aid in committing a crime. But anyway, is CRC really that slow? I know it is a linear calculation, but generally the CRC is computed on individual packets rather than on the whole file. Granted it is not as effective, but it is generally faster. What I'm just saying is, how long is the delay really? And are you also aware that threading can actually be harmful on a single processor system? Using more threads than there are processors can actually make things slower sometimes, and I doubt the majority of mIRC users use MP systems.