Brute force decryption

[gowans07]

Hi, I currently have a legacy application wrote in java and am trying to develop a new updated version of the application. The application relies on inputs from encrypted text files, the only thing is i dont know the type of encryption used in the old application. Is there any way i can go about determining the type of encryption and then brute forcing it? The company that developed the encryption package no longer exists so its obviously impossible to get anywhere that way?

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#TG

[hfx642]

What's the extension? (This may tell you.)
Can you see what is in the header of the file? (The first few characters may tell you.)

[gowans07]

.raw
nope i know what the unencrypted files look like but that doesnt help with the decrpytion surely?

[gusano79]

i know what the unencrypted files look like but that doesnt help with the decrpytion surely?

If the file contains encrypted data only, then you're right. However, the program that saved the file may have included other information with the encrypted data for some reason. It's worth looking at.

[gowans07]

hmm okay, is it worth generating a few files and comparing them, or is it impossible to reverse engineer AES on a small timescale? I've decompiled the java but can't see anything relating to an encryption key. To encrypt the files a "Developer" dongle must be plugged into the machine that the program is ran from, i may see if i can access the contents of that dongle