# Modular reduction in Galois fields

I want to compute x^6 mod x^5+x^2+1 in the Galois Field GF(2^5). Does anyone know how to do this in SAGE?

Modular reduction in Galois fields

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3

First, define `k`

to be the field GF(2^5), whose generator is named `a`

:

```
sage: k.<a> = FiniteField(2^5); k
Finite Field in a of size 2^5
```

Alternatively :

```
sage: k = GF(2^5, 'a'); k
Finite Field in a of size 2^5
```

Then, define the polynomial ring `k[x]`

:

```
sage: R.<x> = PolynomialRing(k); R
Univariate Polynomial Ring in x over Finite Field in a of size 2^5
```

Alternatively:

```
sage: R = k['x']; R
Univariate Polynomial Ring in x over Finite Field in a of size 2^5
```

Then, do your computation in R:

```
sage: P = R(x^6)
sage: P.mod(x^5+x^2+1)
x^3 + x
```

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Asked: ** 2013-04-28 07:04:04 +0200 **

Seen: **1,097 times**

Last updated: **Apr 28 '13**

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