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Spongy Castle is a package-rename (org.bouncycastle.* to org.spongycastle.*) of Bouncy Castle intended for the Android platform. Android unfortunately ships with a stripped-down version of Bouncy Castle, which prevents easy upgrades - Spongy Castle overcomes this and provides a full, up-to-date version of the Bouncy Castle cryptographic libs.

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package org.spongycastle.math.field;

import java.math.BigInteger;

import org.spongycastle.util.Integers;

class GenericPolynomialExtensionField implements PolynomialExtensionField
{
    protected final FiniteField subfield;
    protected final Polynomial minimalPolynomial;

    GenericPolynomialExtensionField(FiniteField subfield, Polynomial polynomial)
    {
        this.subfield = subfield;
        this.minimalPolynomial = polynomial;
    }

    public BigInteger getCharacteristic()
    {
        return subfield.getCharacteristic();
    }

    public int getDimension()
    {
        return subfield.getDimension() * minimalPolynomial.getDegree();
    }

    public FiniteField getSubfield()
    {
        return subfield;
    }

    public int getDegree()
    {
        return minimalPolynomial.getDegree();
    }

    public Polynomial getMinimalPolynomial()
    {
        return minimalPolynomial;
    }

    public boolean equals(Object obj)
    {
        if (this == obj)
        {
            return true;
        }
        if (!(obj instanceof GenericPolynomialExtensionField))
        {
            return false;
        }
        GenericPolynomialExtensionField other = (GenericPolynomialExtensionField)obj;
        return subfield.equals(other.subfield) && minimalPolynomial.equals(other.minimalPolynomial);
    }

    public int hashCode()
    {
        return subfield.hashCode()
            ^ Integers.rotateLeft(minimalPolynomial.hashCode(), 16);
    }
}