使用 PHP 或 JS 解码 Youtube 密码签名的最佳方法

Ciphered signature is actually the scrambled signature which anybody can debug with few sets of working signatures. But Youtube keeps on changing the scrambling algo. I have seen few Youtube video downloader which are working smoothly without being affected through this changing game. I think they are checking the player and extracting the decode script from the player file and hence it keeps them going.

我需要一些有关在这种情况下使用的实际技术的帮助.我知道 'youtube-dl' - 一个用于下载视频的 Python 程序.由于我不擅长python，我认为他们使用的是相同的方法.

function bz(a) {
    a = a.split("");
    a = cz(a, 61);
    a = cz(a, 5);
    a = a.reverse();
    a = a.slice(2);
    a = cz(a, 69);
    a = a.slice(2);
    a = a.reverse();
    return a.join("")
}

function cz(a, b) {
    var c = a[0];
    a[0] = a[b % a.length];
    a[b] = c;
    return a
};