HSMM

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HSMM

Postby VA2KEY » Sat Jun 04, 2011 10:57 am

Just casting out another line to see if there's a level of interest...

Has anyone experimented with the so-called "hinternet" (Ham Internet)?
http://en.wikipedia.org/wiki/High-speed ... edia_radio

Granted it might not involve a lot of soldering, but I suspect it can be a highly technical group activity.

Specifically, I'm wondering if one of the 3rd party firmware projects for off-the-shelf wifi radios (Open-WRT, DD-WRT, Tomato) is preferable from the ham's perspective (control over frequency, power, and antenna diversity).
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Re: HSMM

Postby Eamon » Sat Jun 04, 2011 1:10 pm

One of the drawbacks mentioned is lack of access control in the absence of encryption.

Simply appending a changing authentication token to each packet would accomplish this. If the token were generated with a private key, the counterpart of a published public key, the scheme should be legal, at least according to what I understand of the spirit of the FCC regulations, which require keys to be published allowing the communications to be decrypted.

I have no idea whether Industry Canada has developed a clear position on this akin to what seems to be the case in the US.

Although the Wikipedia article states "Per FCC rules the encryption keys themselves must be published in a publicly accessible place if using WEP, WPA/WPA2 or any other encryption, thereby undermining the security of their implementation.", I should think it would be sufficient to publish the DECRYPTION key.

However I suppose generating an authentication token using PK encryption is too expensive to use on each packet. Or is that no longer the case with modern CPUs?

Of course, from a practical standpoint you could achieve pretty good "security by obscurity" while staying legal, if you were to simply write your own low level cryptographic driver layers, and publish the implemented algorithms (but not the code). The prospect of actually implementing your algorithm would deter all but reasonably dedicated hackers.
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Re: HSMM

Postby Eamon » Sat Jun 04, 2011 1:24 pm

To answer Dan's initial question... I think open-source firmware builds may be the only option if you want to operate out of the normal WiFi bands such as in 802.11 b/g channels "-1" and "0".

Now, what would we want to do with a ham-wifi network?

Even if you don't encrypt your own wireless network, you presumably can't do anything that will involve the exchange of encrypted content. This really restricts what you can do. The anti-encryption regulations were certain written in a different era, before we had ubiquitous encryption within data communication streams.
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Re: HSMM

Postby VA2KEY » Sat Jun 04, 2011 3:15 pm

This is a really relevant question you ask:
"Now, what would we want to do with a ham-wifi network?"

My response to "why do it?" would be some or all of the following:
1- Because it's experimental
2- Because it's radio-related
3- Because I find it interesting

As a new ham discovering the hobby, I get the feeling that some or all of those same reasons are applicable everywhere (I'd be curious to hear the opinions of our experienced hams on this).

But I agree that if the point is to simply create a private network for hams, I would instead explore other options such as darknets.
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Re: HSMM

Postby VA2KEY » Sun Jun 05, 2011 3:25 pm

I believe I have a sufficient answer to the question of which firmware to use.

I happened to start with OpenWRT.
My first test was to see if I could revert back to the Linksys FW from OpenWRT without using special "unbrick" utilities:
1- the hardware "factory reset" button wiped a few settings, but I remained in openWRT land.
2- the Linksys FW it was running out-of-the-box is available from Cisco/linksys but openwrt told me it's an unsupported format.
I didn't try to go from openWRT to other 3rd party FW.

Exploring openWRT a bit, I see that it provides control over antenna diversity: you can let the FW choose or you can force which is used for Tx and which for Rx.
Next, power: you can choose the power expressed in DBm, but it comes with a warning that if you push the HW too much, the magic smoke might come out.
Lastly, frequency: there's a "custom" option but configuration is not as straightforward.

So I think openWRT will meet my requirements for now.

Note about unbricking: I think the HW can be forced into running a tftp client. if there's a local tftp server available to push the FW, the client should blindly load it and reboot.
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Re: HSMM

Postby VE2EVN » Sun Jun 05, 2011 9:19 pm

VA2KEY wrote:Note about unbricking: I think the HW can be forced into running a tftp client. if there's a local tftp server available to push the FW, the client should blindly load it and reboot.

Most Linksys routers have a TTL serial port on the PCboard used especially for that purpose (unbricking) which many times is the only thing that works.
If you ever brick it, let me know.. I know the procedure and what cable to use.

Marc-Andre
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Re: HSMM

Postby naveen » Tue Jun 28, 2011 9:36 am

[quote="VA2KEY"]Just casting out another line to see if there's a level of interest...

I am interested!

As for unbricking, I already own a couple of routers which I just modded to enable rs232 from TTL that was available on the PCB. I plan to post a description of this process somewhere, though it was really simple, just use a max3232 and follow the datasheet. This will allow me to see better what's going on when flashing/resetting the boxes.

Actually, before I had this rs232 port enabled, there was a method that involved sniffing for a UDP packet, and then hitting/releasing the reset button with precise timing, which then allowed one to telnet into the router to reset it.

Anyway, as for the HSMM project, this looks great!

cheers,

Naveen
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Re: HSMM

Postby Eamon » Tue Jun 28, 2011 2:40 pm

Here are a few facts I found in the last month or so of looking into ham wifi.

The thing I'm specifically addressing is techniques for extending range.

Using a wifi device according to its original license-exempt certification, limits your ERP to I think around 23dBm, or about 200mW. Note this is considerably higher than what is allowed for non-spread-spectrum license-exempt devices in the 2.4GHz ISM band.

The amateur allocation in both Canada and USA starts below the bottom end of the 2.4GHz license-exempt band, and partially overlaps this band. I forget the exact frequencies, but I remember the conclusion: it appears, given the channel center frequencies, the bandwidth of WiFi, and the edge of the amateur allocation, that it's possible to use channels 1 up through 5 on an amateur license.

This means you can use significantly higher ERP - either with highly directional antennas, or with more power, as long as you adhere to the requirements of station identification, transparency of content, no commercial use etc.

I have found one or two web pages which mention that some routers or dongles have an exposed T/R signal which can be used to control an external power amp.

Of course, if you were to use high powered wifi you could easily wipe out any nearby wifi router on the same channel. Although this might not be a nice thing to do, from reading the regulations it appears that licensed operators have no responsibility to avoid interfering with the operation of license-exempt apparatus.

I have done some research and can find the references for all of this if anyone is interested, but I don't have them handy right now since I am on my computer at work. Email me or reply to the post if you want more information on an of this.
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Re: HSMM

Postby VA2KEY » Wed Jun 29, 2011 8:16 pm

Eamon,

I think it would be great if you were to document your findings and conclusions.
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Re: HSMM

Postby naveen » Wed Jun 29, 2011 9:19 pm

Hi Dan,

What settings are you using for HSMM functionality in openwrt? Do you need to enable some feeds/options in the .config?
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