Decrypter.js

function Decrypter() {
    throw new Error('This is a static class');
}

Decrypter.hasEncryptedImages = false;
Decrypter.hasEncryptedAudio = false;
Decrypter._requestImgFile = [];
Decrypter._headerlength = 16;
Decrypter._xhrOk = 400;
Decrypter._encryptionKey = "";
Decrypter._ignoreList = [
    "img/system/Window.png"
];
Decrypter.SIGNATURE = "5250474d56000000";
Decrypter.VER = "000301";
Decrypter.REMAIN = "0000000000";

Decrypter.checkImgIgnore = function(url){
    for(var cnt = 0; cnt < this._ignoreList.length; cnt++) {
        if(url === this._ignoreList[cnt]) return true;
    }
    return false;
};

Decrypter.decryptImg = function(url, bitmap) {
    url = this.extToEncryptExt(url);

    var requestFile = new XMLHttpRequest();
    requestFile.open("GET", url);
    requestFile.responseType = "arraybuffer";
    requestFile.send();

    requestFile.onload = function () {
        if(this.status < Decrypter._xhrOk) {
            var arrayBuffer = Decrypter.decryptArrayBuffer(requestFile.response);
            bitmap._image.src = Decrypter.createBlobUrl(arrayBuffer);
            bitmap._image.addEventListener('load', bitmap._loadListener = Bitmap.prototype._onLoad.bind(bitmap));
            bitmap._image.addEventListener('error', bitmap._errorListener = bitmap._loader || Bitmap.prototype._onError.bind(bitmap));
        }
    };

    requestFile.onerror = function () {
        if (bitmap._loader) {
            bitmap._loader();
        } else {
            bitmap._onError();
        }
    };
};

Decrypter.decryptHTML5Audio = function(url, bgm, pos) {
    var requestFile = new XMLHttpRequest();
    requestFile.open("GET", url);
    requestFile.responseType = "arraybuffer";
    requestFile.send();

    requestFile.onload = function () {
        if(this.status < Decrypter._xhrOk) {
            var arrayBuffer = Decrypter.decryptArrayBuffer(requestFile.response);
            var url = Decrypter.createBlobUrl(arrayBuffer);
            AudioManager.createDecryptBuffer(url, bgm, pos);
        }
    };
};

Decrypter.cutArrayHeader = function(arrayBuffer, length) {
    return arrayBuffer.slice(length);
};

Decrypter.decryptArrayBuffer = function(arrayBuffer) {
    if (!arrayBuffer) return null;
    var header = new Uint8Array(arrayBuffer, 0, this._headerlength);

    var i;
    var ref = this.SIGNATURE + this.VER + this.REMAIN;
    var refBytes = new Uint8Array(16);
    for (i = 0; i < this._headerlength; i++) {
        refBytes[i] = parseInt("0x" + ref.substr(i * 2, 2), 16);
    }
    for (i = 0; i < this._headerlength; i++) {
        if (header[i] !== refBytes[i]) {
            throw new Error("Header is wrong");
        }
    }

    arrayBuffer = this.cutArrayHeader(arrayBuffer, Decrypter._headerlength);
    var view = new DataView(arrayBuffer);
    this.readEncryptionkey();
    if (arrayBuffer) {
        var byteArray = new Uint8Array(arrayBuffer);
        for (i = 0; i < this._headerlength; i++) {
            byteArray[i] = byteArray[i] ^ parseInt(Decrypter._encryptionKey[i], 16);
            view.setUint8(i, byteArray[i]);
        }
    }

    return arrayBuffer;
};

Decrypter.createBlobUrl = function(arrayBuffer){
    var blob = new Blob([arrayBuffer]);
    return window.URL.createObjectURL(blob);
};

Decrypter.extToEncryptExt = function(url) {
    var ext = url.split('.').pop();
    var encryptedExt = ext;

    if(ext === "ogg") encryptedExt = ".rpgmvo";
    else if(ext === "m4a") encryptedExt = ".rpgmvm";
    else if(ext === "png") encryptedExt = ".rpgmvp";
    else encryptedExt = ext;

    return url.slice(0, url.lastIndexOf(ext) - 1) + encryptedExt;
};

Decrypter.readEncryptionkey = function(){
    this._encryptionKey = $dataSystem.encryptionKey.split(/(.{2})/).filter(Boolean);
};