c# script for some app

Decrypt.csx

using System.Security.Cryptography;
using System.IO;

byte[][] LoadKeys(string fn)
{
  var blobKey = new byte[] { 0xE4, 0xC5, 0x1B, 0x30, 0xDB, 0x7E, 0xE, 0x20, 0x15, 0xB5, 0xD8, 0x2E, 0x1A, 0xF6, 0x3F, 0x6E };
  var decrypted = new MemoryStream();
  using(var f = File.OpenRead(fn))
  {
    var iv = new byte[16];
    f.Read(iv, 0, 16);
    using (var aes = new AesCryptoServiceProvider() { Key = blobKey, IV = iv, Mode = CipherMode.CBC })
    using (var dec = aes.CreateDecryptor(blobKey, iv))
    using (var x = new CryptoStream(f, dec, CryptoStreamMode.Read))
    {
      x.CopyTo(decrypted);
    }
  }
  decrypted.Seek(-144, SeekOrigin.End);
  var ret = new byte[9][];
  for(var i = 0; i < 9; i++)
  {
    ret[i] = new byte[16];
    decrypted.Read(ret[i], 0, 16);
  }
  decrypted.Dispose();
  return ret;
}

enum InstrumentType { Guitar = 0, Bass, Drums, Vox };
int GetSoloKey(InstrumentType t){
  switch(t)
  {
    case InstrumentType.Guitar: return 5;
    case InstrumentType.Bass: return 1;
    case InstrumentType.Drums: return 3;
    case InstrumentType.Vox: return 7;
    default: return 0;
  }
}
int GetTrksKey(InstrumentType t){
  switch (t)
  {
      case InstrumentType.Guitar: return 6;
      case InstrumentType.Bass: return 2;
      case InstrumentType.Drums: return 4;
      case InstrumentType.Vox: return 8;
      default: return 1;
  }
}

string GetFileName(string blobName, InstrumentType t, bool trks)
{
  var fn = blobName.Replace(".blob", "");
  string txt = "";
  switch(t)
  {
    case InstrumentType.Guitar: txt = "gtr"; break;
    case InstrumentType.Bass: txt = "bass"; break;
    case InstrumentType.Drums: txt = "drums"; break;
    case InstrumentType.Vox: txt = "vox"; break;
    default: throw new Exception("AAAAAAHHHH!!!!");
  }
  return fn + "_" + txt + "_" + (trks ? "trks" : "solo") + ".dat";
}

void DecryptOgg(string fn, byte[] key){
  using (var f = File.OpenRead(fn))
  using (var o = File.OpenWrite(fn.Replace(".dat",".ogg")))
  {
    var iv = new byte[16];
    f.Read(iv, 0, 16);
    using (var aes = new AesCryptoServiceProvider() { Key = key, IV = iv, Mode = CipherMode.CBC })
    using (var dec = aes.CreateDecryptor(key, iv))
    using (var x = new CryptoStream(f, dec, CryptoStreamMode.Read))
    {
      x.CopyTo(o);
    }
  }
}

void DecryptAll(string baseName, int howMany){
  for(int songNum = 0; songNum < howMany; songNum++)
  {
    var blobName = $"{baseName}{songNum}.blob";
    var keys = LoadKeys(blobName);
    for(var i = 0; i < 4; i++){
      DecryptOgg(GetFileName(blobName, (InstrumentType)i, false), keys[GetSoloKey((InstrumentType) i)]);
      DecryptOgg(GetFileName(blobName, (InstrumentType)i, true), keys[GetTrksKey((InstrumentType) i)]);
    }
  }
}

// DecryptAll(@"G:\Dumps\game.app\a", 15); // decrypt all the songs in the app