Recent content by grappolo

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    Modular multiplication problem in C

    Hi, about sotrage space I'm talking of some Kb depending on the sensing algorithm loaded on the device. My program is only supposed to handle authentication between devices so the space left depends on other software space usage. About efficiency I have no specific costraints, my goal is to...
  2. G

    Modular multiplication problem in C

    My device also offers a very limited storage space and I'm already using part of it for cryptographic material needed by the algorithm. Using a table like the one you're suggesting isn't a good idea in this case (when in a normal situation would have been also my choice probably). At the moment...
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    Modular multiplication problem in C

    You may be right, it can be more efficient. I'll try that tomorrow and I'll compare results using Avrora Simulator. Thank you, Lu
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    Modular multiplication problem in C

    If you mean the basic tecnique of splitting the 16 bit value into two 8 bit value with proper coefficient I've already tried that. The problem is that it isn't efficient since a single multiplication involve a lot more of operation. I don't know about Barrett reduction but Montgomery...
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    Modular multiplication problem in C

    That's the problem Borek. The only way to avoid overflow could be avoiding the use of numbers bigger than 2^8 for a and b but this is impossible in my case. There must be an efficient way to do this. Thank you for your reply anyway. Lu
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    Modular multiplication problem in C

    Hi Borek, n has to be is the largest prime smaller than 2^16; this value is 65521. Also all the values (a and b) are smaller than 65521 (so also smaller than 2^16). Sorry for the missing information :redface:! Lu
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    Modular multiplication problem in C

    Hi to everyone, i'm writing a program in C that is supposed to run on a AVR processor with registers and int of 16 bit (like the one used in some sensor for WSN). This program involves the use of the Lagrange Interpolation. I've worked on it managing to solve most part of the problems but I'm...
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