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[Frama-c-discuss] Arithmetics in finite fields

  • Subject: [Frama-c-discuss] Arithmetics in finite fields
  • From: Boris.Hollas at de.bosch.com (Hollas Boris (CR/AEY1))
  • Date: Mon, 1 Feb 2010 13:29:59 +0100
We have applications where we do arithmetics in GF(2^32). This is easily done with unsigned integers and the standard operations +, *. However, Jessie isn't able to verify arithmetic safety because it doesn't know that we want to compute in GF(2^32). For example, nothing bad can happen in this code

const unsigned long m = 0x10000;

unsigned int foo(unsigned int a) {
  return (((a+1) % m) * ((a+1) % m)) % m;
}


Which is equivalent to


unsigned int foo(unsigned int a) {
  return (a+1)*(a+1);
}


On a platform that uses 32-bit integers. Is there a way to verify arithmetics in GF(2^32) with Frama-C/Jessie?