这是什么算法？

js 代码示例如下：

m = 'a73fB/+LpWMfZ8qw17wtyhU5Ut9onnF1X7vGQyqSRmVquotlVw1HQYhg8czB17isSFoubUS9lP/DT1LdDLLdJyDcaMmpM40u0hNuBNULkExTf03uqsEL18I'
r = 'YgzMGmvoqT9gatEC56wIH0bF80kqlOcj'

var f_iVR2SlRR9weNau1TCve0RWupMxM5U3Rd = function (m, r, d) {
    var e = "DECODE";
    var r = r ? r : "";
    var d = d ? d : 0;
    var q = 4;
    r = md5(r);
    var o = md5(r.substr(0, 16));
    var n = md5(r.substr(16, 16));
    if (q) {
        if (e == "DECODE") {
            var l = m.substr(0, q)
        }
    } else {
        var l = ""
    }
    var c = o + md5(o + l);
    var k;
    if (e == "DECODE") {
        m = m.substr(q);
        k = base64_decode(m)
    }
    var h = new Array(256);
    for (var g = 0; g < 256; g++) {
        h[g] = g
    }
    var b = new Array();
    for (var g = 0; g < 256; g++) {
        b[g] = c.charCodeAt(g % c.length)
    }
    for (var f = g = 0; g < 256; g++) {
        f = (f + h[g] + b[g]) % 256;
        tmp = h[g];
        h[g] = h[f];
        h[f] = tmp
    }
    var t = "";
    k = k.split("");
    for (var p = f = g = 0; g < k.length; g++) {
        p = (p + 1) % 256;
        f = (f + h[p]) % 256;
        tmp = h[p];
        h[p] = h[f];
        h[f] = tmp;
        t += chr(ord(k[g]) ^ (h[(h[p] + h[f]) % 256]))
    }
    if (e == "DECODE") {
        if ((t.substr(0, 10) == 0 || t.substr(0, 10) - time() > 0) && t.substr(10, 16) == md5(t.substr(26) + n).substr(0, 16)) {
            t = t.substr(26)
        } else {
            t = ""
        }
    }
    return t
};