vroid web view vrm decrypt

aes.cs

using System;
using System.Security.Cryptography;
using System.IO;
using System.IO.Compression;
namespace Vroid
{
    class Vroiddec
    {
        static void Main(string[] args)
        {
        	using (FileStream fs = new FileStream(args[0],FileMode.Open)) {
        		using (BinaryReader bs = new BinaryReader(fs)) {
        			int buff_size=(int)(fs.Length)-48;
        			RijndaelManaged rDel=new RijndaelManaged();
        			rDel.IV=bs.ReadBytes(16);
        			rDel.Key=bs.ReadBytes(32);
        			rDel.Mode=CipherMode.CBC;
        			byte[] resultarray=rDel.CreateDecryptor().TransformFinalBlock(bs.ReadBytes(buff_size),0,buff_size);
        			using(MemoryStream ms =new MemoryStream(resultarray)){
	        			using(GZipStream gzs=new GZipStream(ms,CompressionMode.Decompress)){
	        				using(FileStream df=new FileStream(args[0]+".dec",FileMode.OpenOrCreate,FileAccess.Write))
	        				{
			        			int data;
			        			while((data=gzs.ReadByte())!=-1)
			        			{
			        				df.WriteByte((byte)data);
			        			}
	        				}
	        			}
        			}
				}
			}
            log_msg("Done!");
        }
		static void log_msg(string msg)
		{
			Console.WriteLine(msg);
		}
    }
}

VRoid Hub obfuscates the mesh of the preview models. You can read more on this here: https://toon.link/blog/1740863435/borrowing-intellectual-property.

Nice post!

I checked the differences between the downloaded VRM and the VRM in the browser, and found that the vertex coordinate data had undergone some transformations

true dude, I hope this will shows how it works:
https://toon.link/blog/1740863435/borrowing-intellectual-property

Just think this will be helpful? https://inside.pixiv.blog/2024/02/05/120000

now i get a decrypted .bin file. it seems that this .bin file contains a pmx model and its textures and meshes. but i cannnot read this file. hope somebody could give me some suggestions. https://github.com/TenjoinWai/symphony-miku

bumping on this, wondering how the older models are handled