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Posted 10-16-2020 08:27 AM (3933 views) | In reply to LinusH
As pointed out earlier by several people, no way to revert. And it has to be checked where to use MD5 and where not:
It is easy this way to e.g. check if content of a file was modified, so you see a different MD5 value than expected. Or you want to find duplicate files, not by name but by content. Had this yesterday, so MD5 over complete folder structure and show "MD5-hash: filename", sort by hash, see >potential< duplicates. I say potential since of course you have the risk of clashes - different content produces the same hash. Rare but possible, more like the more entries you have. For this careful search to reduce what to look at, MD5 is ideal and very fast.
For that "clash" reason, using an MD5 to shorten concatenated strings used in table JOINs can be very risky depending on data volume. Fell into that trap once at customer site, very hard to identify if you don't know what you are looking at.
Finally, when hearing "reverse an MD5" or similar, first thought is always that someone tries to look at something they should not be looking at...
