Implementation of a RF receiver and transmitter for secure data-exchange.

Discussion in 'Wireless & RF Design' started by kneerajan, Oct 4, 2012.

  1. kneerajan

    Thread Starter New Member

    Oct 4, 2012
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    Hello all,

    I need some help regarding Implementation of a RF receiver and transmitter for secure data-exchange. I am using RFM70 transceiver for wireless data transfer, I am using a microcontroller dsPIC33EPxxxGP504. Please give me some idea how can i transfer secure data. my main aim is to "In „normal operation“ the system shall receive position points and move indepently. Relevant data shall be transmitted to the base station."

    I should progarm in C. If any one can help me with some idea how can i proceed then it would be great.

    Thank you
     
  2. WBahn

    Moderator

    Mar 31, 2012
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    Depending on where you are and what radio service you are doing this under, you may be legally prohibited from transmitting any kind of encrypted waveform. So you had best check into that.

    Assuming there are no legal hurdles, then you have to provide a lot more information than you have. It is just too wide open. Imagine someone asking you for ideas on how to get from their house to an amusement park without crossing any bridges. Your first reaction would be, well, where do you live, where's the amusement park, what does the road network look like, and where are the bridges. The same here. There is way too much you haven't told us. What is the modulation scheme, what is the data rate, what is the basic coding, secure against what threat, and on and on.

    Also, when asking people for free help, don't expect them to track down datasheets in order to get the basic information about the parts you are talking about. Describe the RFM70 a little bit, emphasizing the features that you think might be relevant to the question at hand. Don't worry if you are wrong or don't get everything, the idea is to provide a seed for discussion.
     
  3. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    I don't want to sound argumentative WBahn but do you have any evidence for that?

    With RF data comms I was under the impression that any data you send is your business, provided the transmitters comply with laws regarding the band and output power?

    If what you say is correct then any time a IT software guy changes some compression algorithm on a WiFi communications network somewhere he would be breaking the law?
     
  4. WBahn

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    Mar 31, 2012
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    47 CFR Ch. 1. para 97.113(a)(4)

    Not in general, only in specific application.

    Note that I specifically did not make a blanket statement. First, it is going to depend on what country you are in. Second, it depends heavily on which radio service is being used.

    If this is being done under a ham license in the U.S. then, with specific exceptions (such as sending control transmissions to a satellite), you cannot send transmissions, even by voice, that are intended to obscure the meaning of what was transmitted.

    This causes problems for ARES stations that are trying to provide emergency communications in disaster areas and need to transmit patient info that is covered under HIPPA as confidential but that is needed by the agency that is responding.
     
  5. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    PGP encryption could be performed, then the output is transmitted. You can communicate on the same small bandwidth with everyone no need to have seperate channels, but only your intended recipient can decode the file into something with meaning when using their private key.
     
  6. WBahn

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    Mar 31, 2012
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    That may or may not address the OP's needs. We can't know because the original post is too lacking in relevant information. When they said "for secure data exchange" that leaves just too much open for guessing, which is why I asked the OP to give more details regarding secure against what? In general, "secure data exchange" would have to entail a number of aspects: The bad guys can't tell what you were saying, the bad guys can't modify what you are saying (without you being able to detect it), the bad guys can't pretend to be good guys (without you being able to detect it), the bad guys can't prevent your messages from getting through (without using methods that expose them to risks they aren't willing to accept). There are other aspects that could be important goals as well, for instance making it difficult for the bad guys to even detect that a transmission between good guys is taking place at all. Which of these is of primary concern to the OP is anyone's guess -- it may well be that all they care about is data confidentiality, but that is far from obvious. If the system is supposed to receive position points and then move independently, what is more important: that no else be able to tell what position points were sent, or that no one else can send bogus position points?
     
  7. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    That's Amatuer radio licensing, which is a very specific license to operate as a non-profit public radio station, and can only transmit certain things.

    That licensing does not apply to all the license free data comms like 315MHz, 433MHz, 2.4GHz WiFi etc etc.

    The OP specifically asked about a RFM70 digital transceiver module like this one;
    http://www.hoperf.com/rf_fsk/24g/rfm70.htm
    which operate on the 2.4GHz license free band and has no restriction (that I know of) regarding how the data is encoded or encrypted.

    I would guess more than half of the data sent over 2.4GHz data comm band is "encrypted" in some way, but like most of this post that is *my opinion*.

    If anyone has facts about legality of sending encrypted RF comms data please speak up!
     
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