u3d 加密资源并缓存加载

// C# Example
    // Builds an asset bundle from the selected objects in the project view.
    // Once compiled go to "Menu" -> "Assets" and select one of the choices
    // to build the Asset Bundle 

    using UnityEngine;
    using UnityEditor;
    using System.IO;
    public class ExportAssetBundles {
        [MenuItem("Assets/Build AssetBundle Binary file From Selection - Track dependencies ")]
        static void ExportResource () {
            // Bring up save panel
            string path = EditorUtility.SaveFilePanel ("Save Resource", "", "New Resource", "unity3d");
            if (path.Length != ) {
                // Build the resource file from the active selection.
                Object[] selection = Selection.GetFiltered(typeof(Object), SelectionMode.DeepAssets);
                BuildPipeline.BuildAssetBundle(Selection.activeObject, selection, path, BuildAssetBundleOptions.CollectDependencies | BuildAssetBundleOptions.CompleteAssets);
                Selection.objects = selection; 

                FileStream fs = new FileStream(path,FileMode.Open,FileAccess.ReadWrite);
                byte[] buff = new byte[fs.Length+];
                fs.Read(buff,,(int)fs.Length);
                buff[buff.Length-] = ;
                fs.Close();
                File.Delete(path); 

                string BinPath = path.Substring(,path.LastIndexOf('.'))+".bytes";
 //             FileStream cfs = new FileStream(BinPath,FileMode.Create);
                cfs.Write(buff,,buff.Length);
                buff =null;
                cfs.Close(); 

//              string AssetsPath = BinPath.Substring(BinPath.IndexOf("Assets"));
//              Object ta = AssetDatabase.LoadAssetAtPath(AssetsPath,typeof(Object));
//              BuildPipeline.BuildAssetBundle(ta, null, path);
            }
        }
        [MenuItem("Assets/Build AssetBundle From Selection - No dependency tracking")]
        static void ExportResourceNoTrack () {
            // Bring up save panel
            string path = EditorUtility.SaveFilePanel ("Save Resource", "", "New Resource", "unity3d");
            if (path.Length != ) {
                // Build the resource file from the active selection.
                BuildPipeline.BuildAssetBundle(Selection.activeObject, Selection.objects, path);
            }
        } 

    } 

　　把打包的文件转换成了binary文件并多加了一个字节加密。

　　当bytes文件生成好后再选中它，使用"Assets/Build AssetBundle From Selection - No dependency tracking"再次打包。

using UnityEngine;
using System.Collections;
using System;

public class WWWLoadTest : MonoBehaviour
{

    public string BundleURL;
    public string AssetName;
    IEnumerator Start()
    {
          WWW www =WWW.LoadFromCacheOrDownload(BundleURL,);

        yield return www;

        TextAsset txt = www.assetBundle.Load("characters",typeof(TextAsset)) as TextAsset;

        byte[]  data = txt.bytes;

        byte[] decryptedData = Decryption(data);
        Debug.LogError("decryptedData length:"+decryptedData.Length);
        StartCoroutine(LoadBundle(decryptedData));
    }

    IEnumerator LoadBundle(byte[] decryptedData){
        AssetBundleCreateRequest acr = AssetBundle.CreateFromMemory(decryptedData);
        yield return acr;
        AssetBundle bundle = acr.assetBundle;
        Instantiate(bundle.Load(AssetName));

    }

    byte[] Decryption(byte[] data){
        byte[] tmp = new byte[data.Length-];
        for(int i=;i<data.Length-;i++){
            tmp[i] = data[i];
        }
        return tmp;

    }

}

WWW.LoadFromCacheOrDownload的作用就是下载并缓存资源，要注意后面的版本号参数，如果替换了资源却没有更新版本号，客户端依然会加载缓存中的文件。

www.assetBundle.Load("characters",typeof(TextAsset)) as TextAsset  //characters是加密文件的名字

AssetBundleCreateRequest acr = AssetBundle.CreateFromMemory(decryptedData);

这句是官网最坑爹的，AssetBundle.CreateFromMemory明明返回的是AssetBundleCreateRequest官网却写得是AssetBundle，而且AssetBundleCreateRequest是一个异步加载，必须用协程的方式加载官网也没有提到。跟多兄弟就倒在了这里

完。