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Try to find a rainbow table.
Split the rainbow table into as many equal parts as you want.
Spin up a pyspark or AWS ECR cluster, however you want to do it. You could also use GCP. Write a simple script to loop through the input from the split table and test every input to see if the hashes match. Remember to record the values you tried, and especially any values that match.
I would recommend testing your pyspark script on something small like a 1 or 2 byte hash first just to make sure it's working correctly.
If you can't find a pre-computed rainbow table, you're going to have to do generate your own, which is a separate pyspark script, and can be a real bitch. If you're going to do all that compute, make sure you share the table you generated so that it doesn't go to waste.
Even then, if they knew what they were doing they might have used multiple salts, in which case you're fucked unless you have them.
Whatever you do, I don't recommend trying to run these jobs at home. You will end up ruining your machine with heat by keeping the CPU pegged at 99% for a year or so.
Lastly, I should say... this is like hacking 101 anon. You should know this, and if you don't know these basics you need to go back to the fundamentals, otherwise you will never progress.