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package org.bouncycastle.pqc.crypto.mceliece;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.pqc.math.linearalgebra.PolynomialRingGF2;
public class McElieceParameters
implements CipherParameters
{
/**
* The default extension degree
*/
public static final int DEFAULT_M = 11;
/**
* The default error correcting capability.
*/
public static final int DEFAULT_T = 50;
/**
* extension degree of the finite field GF(2^m)
*/
private int m;
/**
* error correction capability of the code
*/
private int t;
/**
* length of the code
*/
private int n;
/**
* the field polynomial
*/
private int fieldPoly;
/**
* Constructor. Set the default parameters: extension degree.
*/
public McElieceParameters()
{
this(DEFAULT_M, DEFAULT_T);
}
/**
* Constructor.
*
* @param keysize the length of a Goppa code
* @throws IllegalArgumentException if <tt>keysize < 1</tt>.
*/
public McElieceParameters(int keysize)
throws IllegalArgumentException
{
if (keysize < 1)
{
throw new IllegalArgumentException("key size must be positive");
}
m = 0;
n = 1;
while (n < keysize)
{
n <<= 1;
m++;
}
t = n >>> 1;
t /= m;
fieldPoly = PolynomialRingGF2.getIrreduciblePolynomial(m);
}
/**
* Constructor.
*
* @param m degree of the finite field GF(2^m)
* @param t error correction capability of the code
* @throws IllegalArgumentException if <tt>m < 1</tt> or <tt>m > 32</tt> or
* <tt>t < 0</tt> or <tt>t > n</tt>.
*/
public McElieceParameters(int m, int t)
throws IllegalArgumentException
{
if (m < 1)
{
throw new IllegalArgumentException("m must be positive");
}
if (m > 32)
{
throw new IllegalArgumentException("m is too large");
}
this.m = m;
n = 1 << m;
if (t < 0)
{
throw new IllegalArgumentException("t must be positive");
}
if (t > n)
{
throw new IllegalArgumentException("t must be less than n = 2^m");
}
this.t = t;
fieldPoly = PolynomialRingGF2.getIrreduciblePolynomial(m);
}
/**
* Constructor.
*
* @param m degree of the finite field GF(2^m)
* @param t error correction capability of the code
* @param poly the field polynomial
* @throws IllegalArgumentException if <tt>m < 1</tt> or <tt>m > 32</tt> or
* <tt>t < 0</tt> or <tt>t > n</tt> or
* <tt>poly</tt> is not an irreducible field polynomial.
*/
public McElieceParameters(int m, int t, int poly)
throws IllegalArgumentException
{
this.m = m;
if (m < 1)
{
throw new IllegalArgumentException("m must be positive");
}
if (m > 32)
{
throw new IllegalArgumentException(" m is too large");
}
this.n = 1 << m;
this.t = t;
if (t < 0)
{
throw new IllegalArgumentException("t must be positive");
}
if (t > n)
{
throw new IllegalArgumentException("t must be less than n = 2^m");
}
if ((PolynomialRingGF2.degree(poly) == m)
&& (PolynomialRingGF2.isIrreducible(poly)))
{
this.fieldPoly = poly;
}
else
{
throw new IllegalArgumentException(
"polynomial is not a field polynomial for GF(2^m)");
}
}
/**
* @return the extension degree of the finite field GF(2^m)
*/
public int getM()
{
return m;
}
/**
* @return the length of the code
*/
public int getN()
{
return n;
}
/**
* @return the error correction capability of the code
*/
public int getT()
{
return t;
}
/**
* @return the field polynomial
*/
public int getFieldPoly()
{
return fieldPoly;
}
}
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