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Shortwave Trading: The West Chicago Tower Mystery

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Re: Shortwave Trading: The West Chicago Tower Mystery

#111

Post by bobvan13 »

pbhjpbhj wrote: post #106
cat199 wrote: post #83

Earlier quoted context omitted.

It would be extremely trivial to transport a time-keyed, completely random one-time-pad out of band (e.g. over a commodity internet link/vpn) so long as there is sufficient difference in bandwidth, and then simply XOR the data with it.. good luck cracking that. and that's just what a few seconds of thinking came up with.

How do you use a one-time pad on a single bit of data? (Actually I see how that's possible, A XOR B, upticks are 1, etc.) If the pad is coming via a side-channel then the speed increase is limited by that side-channel, you lose all your gains by waiting for the pad, then lose more by decrypting and verifying. That aside my first thought was someone could jam the signal by blasting the receiver with noise; I wonder ho…

A one-time pad is the right idea. I would send it on fiber at night before the markets open and then use bits from it as the market trades. A few MB per day would be plenty, given the dialup-like speeds of shortwave. That would go through a 10 gbps fiber in milliseconds.

The actual encryption of each bit just require an XOR on each end of the link. That's about half a nanosecond on a Xeon or one clock cycle on your FPGA.

A jammer wants to be close to the receiving antenna so he can use less power. Yet he wants to be far away so he's less likely to be caught. Willfully interfering with any any radio service is illegal in any regulatory domain AFAIK.

Re: Shortwave Trading: The West Chicago Tower Mystery

#112

Post by bobvan13 »

wglb wrote: post #57

So why not listen in the vicinity of the towers and deduce what frequency this is on?

Listening is the easy part. But the sender would be foolish not to strongly encrypt what they send. Are you really "listening" if all you get after decoding is pseudo-random bits?

Re: Shortwave Trading: The West Chicago Tower Mystery

#113

Post by tripletao »

bobvan13 wrote: post #111
pbhjpbhj wrote: post #106

Earlier quoted context omitted.

How do you use a one-time pad on a single bit of data? (Actually I see how that's possible, A XOR B, upticks are 1, etc.) If the pad is coming via a side-channel then the speed increase is limited by that side-channel, you lose all your gains by waiting for the pad, then lose more by decrypting and verifying. That aside my first thought was someone could jam the signal by blasting the receiver with noise; I wonder ho…

A one-time pad is the right idea. I would send it on fiber at night before the markets open and then use bits from it as the market trades. A few MB per day would be plenty, given the dialup-like speeds of shortwave. That would go through a 10 gbps fiber in milliseconds. The actual encryption of each bit just require an XOR on each end of the link. That's about half a nanosecond on a Xeon or one clock cycle on your F…

There is no need for a one-time pad. Any good stream cipher works just as well, same as for any other link. Message integrity is a fun question, since you don't want to spend the bits that you'd need for typical levels of security there; but that question is again independent of a one-time pad vs. normal crypto.

Jamming a licensed radio link vital to rich people who routinely deal with the government doesn't sound like a great idea to me.

Re: Shortwave Trading: The West Chicago Tower Mystery

#114

Post by bobvan13 »

tripletao wrote: post #113
bobvan13 wrote: post #111

Earlier quoted context omitted.

A one-time pad is the right idea. I would send it on fiber at night before the markets open and then use bits from it as the market trades. A few MB per day would be plenty, given the dialup-like speeds of shortwave. That would go through a 10 gbps fiber in milliseconds. The actual encryption of each bit just require an XOR on each end of the link. That's about half a nanosecond on a Xeon or one clock cycle on your F…

There is no need for a one-time pad. Any good stream cipher works just as well, same as for any other link. Message integrity is a fun question, since you don't want to spend the bits that you'd need for typical levels of security there; but that question is again independent of a one-time pad vs. normal crypto. Jamming a licensed radio link vital to rich people who routinely deal with the government doesn't sound li…

Good point, a one-time pad is not needed.

Either way, the likelihood of loss between TX and RX means that you can't advance the cipher as bits arrive. I'm thinking you'd have to advance based on GPS-sync'd clocks. Given that each bit is at least 10's of microseconds, GPS sync is plenty good.

Re: Shortwave Trading: The West Chicago Tower Mystery

#115

Post by wglb »

bobvan13 wrote: post #112
wglb wrote: post #57

So why not listen in the vicinity of the towers and deduce what frequency this is on?

Listening is the easy part. But the sender would be foolish not to strongly encrypt what they send. Are you really "listening" if all you get after decoding is pseudo-random bits?

Listening will at least you know the frequency and type of modulation so you can at least understand who it is. And if the signal is always on or at certain times of the day only can help identify purpose
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