I'm looking for a library that is able to do exact calculations on large finite fields such as GF(2128)/𝔽2128 and GF(2256)/𝔽2256. I listed the features that I need and the features that would be cool below. Obviously, the library should be as fast as possible :-). Ah, since I'm no C++ master (and probably most of the libraries are C++), sample code of say generate a random element/a constant and multiply it to it's multiplicative inverse
x^(-1)
GF(2) (also denoted , Z/2Z or ) is the finite field of two elements (GF is the initialism of Galois field, another name for finite fields). Notations Z2 and. may be encountered although they can be confused with the notation of 2-adic integers.
The order of a finite field refers to the number of elements in the field. So the order of GF(2n) is 2n. More particularly, the bitwise operations needed for directly multiplying two bit patterns in GF(2n) are specific to the irreducible polynomial that defines a given GF(2n).
GF( ) is called the prime field of order , and is the field of residue classes modulo , where the elements are denoted 0, 1, ..., .
F2, the chemical formula for fluorine. or GF(2), in mathematics, the Galois field of two elements. F2, a category in the Fujita scale of tornado intensity.
The NTL library seems to work, using this (sorry I'm quite unable to program in C++) code
#include <NTL/GF2E.h>
#include <NTL/GF2EX.h>
#include <NTL/GF2X.h>
#include <NTL/GF2XFactoring.h>
NTL_CLIENT
int main()
{
GF2X P = BuildIrred_GF2X(256);
GF2E::init(P);
GF2E zero = GF2E::zero();
GF2E one;
GF2E r = random_GF2E();
GF2E r2 = random_GF2E();
conv(one, 1L);
cout << "Cardinality: " << GF2E::cardinality() << endl;
cout << "ZERO: " << zero << " --> " << IsZero(zero) << endl;
cout << "ONE: " << one << " --> " << IsOne(one) << endl;
cout << "1/r: " << 1/r << ", r * (1/r): " << (r * (1/r)) << endl;
cout << "1/r2: " << 1/r2 << ", r2 * (1/r2): " << (r2 * (1/r2)) << endl;
}
it seems to work, proof (output of this program):
Cardinality: 115792089237316195423570985008687907853269984665640564039457584007913129639936
ZERO: [] --> 1
ONE: [1] --> 1
1/r: [0 1 0 1 1 0 1 1 1 0 1 1 1 0 0 1 1 0 1 1 1 0 1 1 0 0 0 0 0 1 0 1 0 1 1 0 1 1 0 0 0 0 0 0 1 1 1 0 1 1 1 0 1 0 1 0 0 0 1 1 1 0 1 1 1 1 0 1 0 1 0 1 1 0 1 1 1 0 0 0 1 0 0 1 0 1 1 1 0 1 1 0 1 1 0 0 0 0 0 1 1 0 1 0 1 0 0 0 0 0 1 0 0 1 1 0 0 1 0 0 1 0 1 1 1 1 0 0 1 1 0 1 0 1 1 1 1 1 1 0 1 1 0 0 0 0 0 1 1 0 1 0 0 1 1 1 0 1 1 1 1 1 0 1 0 1 0 0 0 1 1 0 0 1 1 0 0 1 0 1 1 1 0 1 1 1 1 1 0 1 1 0 1 1 1 1 0 1 0 0 0 0 1 1 1 0 1 1 1 0 1 1 1 1 1 1 1 1 0 1 0 1 0 0 1 1 0 1 1 0 1 1 1 1 1 0 0 1 1 0 1 0 1 0 0 0 0 1 1 0 0 1 1 1 0 1], r * (1/r): [1]
1/r2: [1 0 1 1 0 0 0 0 1 0 1 0 0 0 1 0 0 0 1 1 0 0 1 0 1 0 0 0 1 1 1 0 0 0 1 1 1 1 1 0 1 0 1 1 0 0 1 1 1 0 1 0 1 0 0 1 0 0 0 0 1 1 1 0 0 0 1 1 1 1 1 0 0 1 0 0 0 1 1 0 1 0 1 1 1 0 0 1 0 1 0 1 0 0 1 0 0 0 1 0 0 1 1 1 1 1 0 0 0 0 1 1 1 0 1 0 1 0 1 0 0 0 1 0 1 0 1 1 0 0 0 1 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 1 1 1 0 1 1 0 0 0 0 1 1 0 1 1 1 0 1 0 0 0 0 0 1 1 0 1 1 1 0 0 0 0 1 1 0 1 0 0 0 0 1 0 0 0 0 1 1 1 1 1 0 1 0 1 1 0 1 0 1 0 1 1 1 1 0 0 1 1 0 1 1 1 1 1 0 1 1 1 0 1 0 0 0 0 1 0 1 1 0 0 0 1 1 0 0 1 1 0 1 0 0 1 0 1 0 0 1 1], r2 * (1/r2): [1]
Even inverting seems to work (scroll as right as possible in the output sample above) :-)
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