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by earise at 4:36 AM EDT on September 6, 2017
@datschge Sorry I dont know which one either. I happened to find it on 2ch, he said the key was the same as the key in the game Hortensia Saga which i also found in the same thread
by datschge at 5:10 PM EDT on September 7, 2017
@earise - Thanks, that's good info nonetheless. Hortensia Saga appears to be a hybrid app as well so the key may actually be shared by all those hybrid apps, likely due to using the same framework.
Edit: Actually both are by the same developer, f4samurai.

edited 6:20 PM EDT September 7, 2017
by bnnm at 4:43 AM EDT on September 17, 2017
Heads up, the latest vgmstream autodetects known keys so shouldn't need .hcakey anymore in many cases.
by datschge at 7:47 AM EDT on September 18, 2017
@bnnm - That's great. What is it based on though, do you collect and include the keys right in vgmstream?
Edit: Never mind, just saw you did answer that already in the vgmstream thread.

edited 10:09 AM EDT September 18, 2017
Decrypt by chrrox at 8:59 PM EDT on September 18, 2017
Can anyone decrypt this file if so ill upload the games sound track.

https://assets-sakasho.cdn-dena.com/1246/20170911202918/android/snd/bgm/cs_w_0001!s1ae3f3c0z!.acb

https://assets-sakasho.cdn-dena.com/1246/20170911202918/android/snd/bgm/cs_w_0001!s22c1b0f4z!.awb
by datschge at 6:11 AM EDT on September 19, 2017
@chrrox - What's the game (ideally its android id)? With only the encrypted files nobody has the actual data needed to look for the key.
by chrrox at 5:27 PM EDT on September 19, 2017
@datschge its this game
https://play.google.com/store/apps/details?id=com.dena.a12024374&hl=ja


edited 5:28 PM EDT September 19, 2017
by furrybob at 5:41 PM EDT on September 21, 2017
@bnmm
What's your method for testing each key?

In VGAudio, I unpack a few frames without decoding the entire frame, and if there are an arbitrary number (10 ATM) of frames that unpack successfully, the key's marked as valid.

https://github.com/Thealexbarney/VGAudio/blob/ca7e7358cf8df8ccf9e7f99d0b090b91a51a15e0/src/VGAudio/Codecs/CriHca/CriHcaEncryption.cs#L25
by bnnm at 6:50 PM EDT on September 21, 2017
@furrybob - vgmstream's HCA decoder will (AFAIK) always decode even with an invalid key, but I observed there would be a bunch of clipped samples (0x8000/0x7FFF).

So for each key I just decode frames (max ~100) until a number of non-blank samples (~10*1024) and see how many clipped. The key with lowest number gets picked.

Not super great but seems fast enough and worked with all my files. Usually the correct key gets 0 clips and gets immediatedly selected. I guess a wrong key could still get 0 clips in the first frames so the values can be adjusted though.

(see here).

I tried to check VGAudio for inspiration but the whole ReadSpectralCoefficients was way beyond me, so I just devised this funny thing.
by kode54 at 7:01 PM EDT on September 21, 2017
Also, it doesn't matter to the decoder if it unpacks successfully or not, since the checksum verification happens before the decryption occurs.

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