(MH4U savegame decrypt) How to XOR a keystream from a Repeating CTR Fail savegame to decrypt it?

Discussion in '3DS - ROM Hacking, Translations and Utilities' started by lucoia, Apr 21, 2015.

  1. lucoia

    lucoia Advanced Member

    Nov 29, 2008
    United States
    So I followed this tutorial:


    to make my MH4U .3dz legit dump from original EUR cartridge save in the old Repeating CTR Fail and that worked, I played all the tutorial for 20 minutes and the game is working fine.

    The savegame can now be opened with 3DSExplorer and I can extract key and image bins too.

    I also followed this:


    and I found a file splitting tool simply called Free File Splitter to make the 512 bytes chunks.

    With Ultracompare I also found my keystream which is also present on the key.bin extracted with 3DSExplorer.

    Now what I'm not albe to find is a tool that can XOR that keystream from the savegame to decrypt it.

    How can I do that? Are there such tools around?
    Margen67 likes this.
  2. gamesquest1

    gamesquest1 Nabnut

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    Sep 23, 2013
    well iirc 3dsexplorer just decrypts its by default so you can get the decrypted files.....problem is the saves are still signed so editing the saves that way is sort of pointless as you would still need something like SDF to re-import the save.....so you should really just use SDF to extract them in the first place too and not have to worry about making the game use 1.x encryption as SDF can decrypt anyway
  3. lucoia

    lucoia Advanced Member

    Nov 29, 2008
    United States
    So I can just use SDF and extract the user1 from every savegame version.

    Still the user1 got another layer of encryption, I suppose there's no way to encrypt the user1 in plaintext yet then?

    So, if I want to just mess with the user1 one little change at a time to see what I can change and then convert it back to .sav by reimporting it with SDF is still the best shot I can have instead of trying to modify the .sav in the first place, (which I did already and I posted my results on another topic days ago) is that right?
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