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Comment by h0ba | Hacker News Reader

I wonder if they take the extra time and latency to encrypt their traffic.

Is it possible to intercept a message by flying a drone in the path of the microwaves?

Interception is one thing, but I'm pretty sure that covertly interfering with the link (injecting data both ways, for a long-ish time) would be pretty interesting...

Yes, it could be encrypted using low-latency HW implementations. However, I'd be surprised if these actually perform all the necessary steps to establish a truly secure link (like use message authentication besides encryption, and such).

There's no point in encrypting the traffic. It's publicly-available data. The purpose of the towers is merely to ensure that their owners receive the data a couple of milliseconds before everyone else.

Then how for they stop free riders?

You could probably do the encryption very cheaply from a latency perspective (use AES to generate a key stream that you XOR with the output data, which could easily fit on a sending/receiving FGPA without introducing any significant delay), but in general I would think that it is far more trouble than it is worth.

All these features would require testing, and availability is pretty important for this kind of stuff.

The encryption would take too long.

I don't think the data is going to be very useful. Your interception would block the signal, so this would be a very temporary exercise.

They are using the towers to transmit information from the exchanges (already publicly available) and their own transactions (soon to be publicly available).

One use for this information might be to beat the low-latency masters at their own game, and act on their trades before they arrive.

It's theoretically possible you could design a system which would relay exchange data from the drone at such low latency you could compete with or beat other data feeds for a given location. That would be a valuable commodity, but hard to capitalise on in the short period of time between the drone blocking the signal and the data being re-routed.

It sounds as if anyone with the capability to use the intercepted data would do better using their efforts elsewhere.

I would be pretty simple. You use a high-latency channel with "proper" encryption and authentication to stream a one-time pad key; then encryption and decryption would be a simple XOR, plus a bit of synchronization (to know where in the key stream you are). Doesn't sound like it would introduce much latency.

That method is missing any sort of message authentication. Knowing the framing, one could easily flip a buy to a sell, etc.

One-time pads are only useful if they're not re-used.

Or are you suggesting that the high-latency link is higher throughput, and provides constant gigabytes of pad material? (Eg, stream cipher)

There is already a second fibre link in these setups that has higher throughput and not much more latency.

A microwave link is much lower bandwidth than the optical fiber that already exists to connect the two points (you can't rely solely on microwave, you need fiber to back it up when it rains or is cloudy, etc.).

Also, depending on the market, you're only trading 8 or so hours a day. You can just send the pad during the 16 hours of the day while the link is otherwise unused.

I don't think the one-time pad is necessary here, since the aspect that makes it low-latency is reducing the critical path impact to an XOR at each end. I believe there are various existing encryption schemes which already have this property.

Legal problems and technical problems aside, what are you going to gain by intercepting the traffic? Most of the traffic is going to be market data and order data which are public information (well, order data is public once it hits the exchange). You can take advantage of knowing about order data before it hits the exchange but then you'd have to transmit that information extremely fast, which using a drone (and against those huge radio tower) is going to be pretty much impossible.

You could intercept and then re-emit false market data, then trade against whatever position this puts the users of that data in.

Whether you could do this, and do it without being noticed, I'm not so sure.

You're going to use ... what ... to re-remit false market data? A model airplane, compared to a giant tower designed to send microwaves over vast distances. Sure, that sounds possible. As for intercepting the signal for profit ... what are you going to do with it? The microwaves are already the shortest path.

I agree, it would be technically difficult.

My point is that there is a mechanism by which you could profit: false market data. Whether you could remain undetected and whether this could actually be implemented technically, legally or logistically seems uncertain.

I like the drone idea, but it wouldn't have enough power... Unless it was stationed right by the receiver, where it wouldn't need too much?

This is the secret radio tower which the government used to intercept thousands of trunk phone lines running through Britain to the Republic of Ireland.

http://www.lamont.me.uk/capenhurst/original.html

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