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knightofoldcode
08-06-2005, 04:47 PM
Board,

I purchased a pair of transmitter/reciever's for a different application, however after having recieved them, I'm likly to purchase more for a different purpose.

I was disappointed in the lack of any information on the units..... anywhere. Apparantly, Parallax obtains these units from rfdigital.com as the PCB for the reciever has rfdigital.com on it. However, Linx makes the keyfob, and the IC for the reciever that rfdigital.com has.


I found out the following primary points.
1) These units can be used for a "secure" type item. The product is designed for use in alarm systems and things of this nature. So long as you change the address.
2) Multiple transmitters (keyfobs) can be used with one reciever.
3) The data is encoded. And hack resistant. I say hack resistant because nothing is hack proof. Ask DirecTV.
4) You can change the address's of the units, so that you can use multiple transmitters/recievers that are independant of each other, if you want. (IE, My parents live next door, so I can have one and they can have one and no interference.)
5) Unfortunate part. There is 1024 different possibilities. This is almost small enough to have someone determined to sit there are attempt to find the correct code. Unlikly, but I'd be happier if it had one or two more bits.

I'd really appreciate it if this info was on the webpage. I've included a jpg set of the manual's of the keyfob. I have cut the traces as described in this manual on both the reciever and transmitter and successfully changed the address of my system.

Just wanted people to have access to this information. :)

www.parallax.com/detail.asp?product_id=28004 (http://www.parallax.com/detail.asp?product_id=28004)
www.parallax.com/detail.asp?product_id=28005 (http://www.parallax.com/detail.asp?product_id=28005)
www.linxtechnologies.com (http://www.linxtechnologies.com)

Knight.

Post Edited (knightofoldcode) : 8/6/2005 8:51:19 AM GMT

Paul Baker
08-06-2005, 09:51 PM
Secure keyless entry systems such as those used on automobiles, employ something called a rolling or hopping code algorithm which generates a unique address each time the button is pressed. This makes the hacking method of sniffing the air for the RF code useless because that code once used, will no longer work (average use of these systems the entire rolling code list is traversed and repeated approximately every 14 years). This is a major feature of such systems and companies proudly display this functionality. The fact there is no mention of this in the product sheet, leads me to believe that it does not have this functionality. If such security is important to you (like a keyless entry to your home) you should get a unit which has this functionality.

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1+1=10

Post Edited (Paul Baker) : 8/6/2005 1:54:40 PM GMT

knightofoldcode
08-07-2005, 06:50 AM
Paul Baker said...
Secure keyless entry systems such as those used on automobiles, employ something called a rolling or hopping code algorithm which generates a unique address each time the button is pressed. This makes the hacking method of sniffing the air for the RF code useless because that code once used, will no longer work (average use of these systems the entire rolling code list is traversed and repeated approximately every 14 years). This is a major feature of such systems and companies proudly display this functionality. The fact there is no mention of this in the product sheet, leads me to believe that it does not have this functionality. If such security is important to you (like a keyless entry to your home) you should get a unit which has this functionality.



I agree completly. And I know that it's not a code hopping system. :(

However I can't find anything that does this. At the moment I'm just using it to turn on and off my air compressor's solenoid, for a upcoming halloween project, and was considering using it for my home alarm system, but I think the security is just too low to use it for that application, after having considered it over the last day.

However, it does still give the option of preventing multiple transmitters/recievers from interfering with others. :)

Do you, or anyone else know of a code hopping system for BS users?

Knight.

Paul Baker
08-07-2005, 02:25 PM
I seem to remember seeing one a while back in a hobbyists web site (not specifically designed for use in a BS2). Ill add it to items I will look for members (I promised to track down a surplus VFD I saw recently for Bean).

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1+1=10

knightofoldcode
08-07-2005, 04:24 PM
Paul Baker said...
I seem to remember seeing one a while back in a hobbyists web site (not specifically designed for use in a BS2). Ill add it to items I will look for members (I promised to track down a surplus VFD I saw recently for Bean).


Cool, cool. :)

If you can't, it's not a big loss. I think RFID is the way to go. :) I just wish it was a little longer range.... :( That way I could keep it in my pocket.

As it stands, when you want to open the door, it'll be something like the old Monty Python skit.... "I wave my private parts in your general direction!".....

I assume, in your opinion that the RFID module (the reader and transmitter's sold by Parallax) is secure for house security?

TIA,
Knight.

cyberbiota
08-07-2005, 11:38 PM
Knoight-

Microchip manufactures a product line they call KEELOQ which might be what you are after. They have a variety of code-hopping encoders/decoders/transcoders that are available as single chip solutions. While they are not designed specifically for use with the STAMP, I am sure they are designed to function with Microchip PIC controllers, which are at the heart of several of the Parallax STAMP products. Check out the security products section of their website at:

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=77

peter

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Peter C. Charles

Director, Research and Technology
CyberBiota, Incorporated
Peter.charles@cyberbiota.com (mailto:Peter.charles@cyberbiota.com)
http://www.cyberbiota.com (http://www.cyberbiota.com)