If you are trying to establish a VPN connection in VPN Tracker and you are getting a "Hash Mismatch" error, here is what you need to know:
Hash Mismatch usually means that the Pre-Shared Key (PSK) being used is wrong. When you get the "Hash Mismatch" error, the Hash algorithm is being rejected. However, this is not due to choosing an incorrect "Hashing" algorithm for Phase 1. If the Hashing algorithm chosen is actually wrong, then you would receive an error that would say "No Proposal Chosen" rather than a "Hash Mismatch" error. This would suggest that the client and gateway could not agree on common crypto settings. On the other hand, Hash Mismatch actually means that the hash your gateway calculated doesn't match the hash that VPN Tracker calculated (the two hashes are simply not matching). This hash is calculated out of values exchanged between the client and the gateway and the Pre-Shared Key. As all other values have just been exchanged and have been verified by both sides to be correct (so these cannot cause a different hash, not unless either side has a terrible bug). The only value that isn't exchanged and cannot be checked in advanced is the Pre-Shared Key (PSK).