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 };