Finite Fields

CaC


A group must follow the following rules

Associativity:

Associativity

Identity element:

Identity

Inverses:

Inverse

Abelian group

An abelian group is also commutative:

Commutative

Field

A field is a 5-tuple

$$(F, +, \times, 0, 1)$$

with

  1. $(F, +)$ being an Abelian group with identity 0

    e.g. $1+0=0+1=1$

  2. $(F*, \times)$ being an Abelian group with identity 1

    e.g. $2\times 1=1\times 2 = 2$

  3. Multiplication distributes over the addition

Multiplication distributes

Galois field

Theorem

Any finite field is of order $q=p^m$, where p is a prime number and m is an integer $\geqslant 1$. All fields of a given size are the same.

These have two different notations that mean the same thing, $GF(q)$ and $\mathbb{F}_q$

Extension field

Primitive and Irreducible

Addition

Multiplication

Properties

Multiplicative structure

Multiplicative cycle

Additive structure

Additive structure