Muxtape unraveled


I’ve seen a lot of attention paid to Muxtape over the past few days, and I agree: it’s nice! I think a lot of the romanticism that people attach to the mixtape format is silly, and that removing portability from the equation makes it a lot less useful. But Muxtape is clean and built around an attractively simple idea.

I will say, though, that it does even less than usual to prevent the files it stores from being downloaded. If you fire up Firebug after you start a song playing, it’s easy enough to find the Flash player, which is being passed a set of parameters that look like this:


If you pull out the file parameter and decode it, it looks like this:

Yes, really. I’ve changed enough of the URL to make it invalid, but still: asking is probably not going to be enough.

I’ll admit that this is a hard problem to solve. Unless you’re prepared to undertake a major software development project whereby you decrypt your data client-side and send raw PCM to the sound card — and trust me, you’re probably not — you’re going to be stuck using Adobe Flash to play music in-browser. And if that’s the case, you’re pretty much stuck using a command that amounts to:


This is not very secure — Flash needs to get that URL from somewhere, and if the user can figure it out they can download the file as easily as Flash can. All you can do at THAT point is hiding the name of the file by changing it so quickly that a user’s browser can be bothered to figure it out, but the user herself cannot (this is what iMeem and MySpace do). You’ll probably also insert some hoops that Flash has to jump through to prove its Flash-iness, all of which can be easily faked but which will at least discourage casual downloading.

But the guy running Muxtape has screwed himself out of these measures by using Amazon S3 to store his files, which is handy and cheap but can’t implement a system for changing filenames rapidly, or employ HTTP user agent filtering, or check for tokens, or really do any other server-side cleverness. So the only option he has left is simply asking people not to download. Which I admire, because all of these countermeasures, even the encryption, can be defeated. But I doubt the record companies are going to be as sanguine about it.

But who knows! Maybe he’ll be able to figure out some sort of promotional detente the way the Hype Machine folks have. I hope so. But right now it will be pretty easy for someone to write a Greasemonkey script to allow direct downloading, or for music bloggers looking for free storage to hotlink the site to death.

About the author

Tom Lee


  • What I find most interesting in this series of posts is your complete understanding of the underlying issues involved in all of these music sites.
    If you get what the issues are, and like the services in question, why do this?
    We already know you are smart with cool Dorkbot projects and sophisticated professional work, and don’t need to be reminded of it each time you disassemble a music service.
    What do you want to accomplish or discuss with these posts? I really want to know.

  • These posts are incredibly useful and informative, Tom.
    From the perspective of anyone (anyone other than the hypemachine guys who apparently know all this already) thinking about trying to build some kind of large-scale dynamic website serving a mix of public and private data, it’s really great to see all this stuff worked out explicitly.
    It’s not just about music and flash music players. Writing this stuff out is, without a doubt, a public service. Thank you for spending the time and energy to do it!

  • Why do you have to be such a Debbie Downer?
    All good developers know that you can scrape XSPF playlists and just about anytime you are hosting media files and have a Flash player, people can exploit that.
    Do you have insight on a way to prevent this or do you just like pointing out the obvious?
    I applaud the Muxtape developer for building and shipping a simple, cool app that is easy to use and actually useful to the general public.

  • I agree that these posts are very useful. What is wrong with discussing the nuts and bolts?
    Is Anthony V. suggesting that you are somehow doing something wrong by explaining how the technology works?
    Also – keep in mind that Muxtape looks at the user agent – and in the case of an iPhone, it simply pumps the mp3 straight through- avoiding Flash player altogether.

By Tom Lee