如何解密签名并添加到目标c中的YouTube提取的URL？

我想在我的应用程序中播放youtube视频.一切正常.但是当我试图观看包含youtube内容的视频时.它失败.

我研究发现有人认为你应该加密和解密签名并将其添加到URL？

我不知道如何decrypt signature在IOS？

http://www.youtube.com/get_video_info?video_id=uuZE_IRwLNI&el=vevo&ps=default&eurl=&gl=US&hl=en

stream

 {
    "fallback_host" = "tc.v12.cache7.googlevideo.com";
    itag = 22;
    quality = hd720;
    s = "8E6E5D13EB65FB653B173B94CB0BCC3A20853F5EDE8.5E2E87DF33EEDE165FEA90109D3C7D5DADA06B6BB60";
    type = "video/mp4; codecs=\"avc1.64001F, mp4a.40.2\"";
    url = "http://r7---sn-cvh7zn7r.googlevideo.com/videoplayback?pcm2fr=yes&sver=3&expire=1393773646&itag=22&id=bae644fc84702cd2&upn=SjZd81MudQs&sparams=gcr%2Cid%2Cip%2Cipbits%2Citag%2Cpcm2fr%2Cratebypass%2Csource%2Cupn%2Cexpire&ms=au&gcr=in&mt=1393747698&source=youtube&ratebypass=yes&ipbits=0&fexp=935620%2C919120%2C912523%2C932288%2C914084%2C916626%2C937417%2C937416%2C913434%2C932289%2C936910%2C936913%2C902907&mv=m&key=yt5&ip=103.250.162.79";
}

当我用url它不玩.有什么办法吗？