I wrote a program (in Delphi 7) and have been using it for ages to encrypt then decrypt an executable file, then compare
the hash of the decrypted file with the original. Specifically:
Compute the hash of a file, save it. Let's call it "OldHash"
Encrypt the file in place
Decrypt the file in place
Compute the hash of the file, let's call it "NewHash"
Compare OldHash and NewHash.
In XP (SP3 now, but all SPs AFAIK): OldHash = NewHash.
In Vista: OldHash <> NewHash.
In both cases the decrypted file appears to be in good order - i.e. it executes
OK and shows no practial differences.
To make the comparisons, I have prepared a folder which contains only the Launcher (which does the encrypt/decrypt) the
target exe file and a couple of files which are needed for the exe to run (they are, in fact untouched in these tests).
Then I copy this folder from a machine running XP to a machine running Vista Business and get different results.
Any ideas?
Many thanks,
Rob
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