private String uc_authcode(String string, String operation, String key, int expiry) {

    byte ckey_length = 1;
    key = this.md5(key != null?key:UC_KEY);
    String keya = this.md5(this.substr(key, 0, 16));
    String keyb = this.md5(this.substr(key, 16, 16));
    String keyc = "a";
    String cryptkey = keya + this.md5(keya + keyc);
    int key_length = cryptkey.length();
    string = operation.equals("DECODE")?this.base64_decode(this.substr(string, ckey_length)):this.sprintf("%010d", (long)(expiry > 0?expiry:0)) + this.substr(this.md5(string + keyb), 0, 16) + string;
    int string_length = string.length();
    StringBuffer result1 = new StringBuffer();
    int[] box = new int[256];

    for(int rndkey = 0; rndkey < 256; box[rndkey] = rndkey++) {
        ;
    }

    int[] var19 = new int[256];

    int j;
    for(j = 0; j <= 255; ++j) {
        var19[j] = cryptkey.charAt(j % key_length);
    }

    j = 0;

    int a;
    int result;
    for(a = 0; a < 256; ++a) {
        j = (j + box[a] + var19[a]) % 256;
        result = box[a];
        box[a] = box[j];
        box[j] = result;
    }

    j = 0;
    a = 0;

    for(result = 0; result < string_length; ++result) {
        a = (a + 1) % 256;
        j = (j + box[a]) % 256;
        int tmp = box[a];
        box[a] = box[j];
        box[j] = tmp;
        result1.append((char)(string.charAt(result) ^ box[(box[a] + box[j]) % 256]));
    }

    if(!operation.equals("DECODE")) {
        return keyc + this.base64_encode(result1.toString()).replaceAll("=", "");
    } else {
        String var20 = result1.substring(0, result1.length());
        return (Integer.parseInt(this.substr(var20.toString(), 0, 10)) == 0 || Long.parseLong(this.substr(var20.toString(), 0, 10)) > 0L) && this.substr(var20.toString(), 10, 16).equals(this.substr(this.md5(this.substr(var20.toString(), 26) + keyb), 0, 16))?this.substr(var20.toString(), 26):"";
    }
}