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The Bouncy Castle Java APIs for CMS, PKCS, EAC, TSP, CMP, CRMF, OCSP, and certificate generation. This jar contains APIs for JDK 1.5 and up. The APIs can be used in conjunction with a JCE/JCA provider such as the one provided with the Bouncy Castle Cryptography APIs.

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package org.bouncycastle.pqc.asn1;

import java.math.BigInteger;

import org.bouncycastle.asn1.ASN1EncodableVector;
import org.bouncycastle.asn1.ASN1Integer;
import org.bouncycastle.asn1.ASN1Object;
import org.bouncycastle.asn1.ASN1OctetString;
import org.bouncycastle.asn1.ASN1Primitive;
import org.bouncycastle.asn1.ASN1Sequence;
import org.bouncycastle.asn1.DEROctetString;
import org.bouncycastle.asn1.DERSequence;
import org.bouncycastle.asn1.x509.AlgorithmIdentifier;
import org.bouncycastle.pqc.math.linearalgebra.GF2mField;
import org.bouncycastle.pqc.math.linearalgebra.Permutation;
import org.bouncycastle.pqc.math.linearalgebra.PolynomialGF2mSmallM;

/**
 * Return the keyData to encode in the PrivateKeyInfo structure.
 * 
 * The ASN.1 definition of the key structure is
 * 
 *  *   McElieceCCA2PrivateKey ::= SEQUENCE {
 *     m             INTEGER                  -- extension degree of the field
 *     k             INTEGER                  -- dimension of the code
 *     field         OCTET STRING             -- field polynomial
 *     goppaPoly     OCTET STRING             -- irreducible Goppa polynomial
 *     p             OCTET STRING             -- permutation vector
 *     digest        AlgorithmIdentifier      -- algorithm identifier for CCA2 digest
 *   }
 * 
 */
public class McElieceCCA2PrivateKey
    extends ASN1Object
{
    private int n;
    private int k;
    private byte[] encField;
    private byte[] encGp;
    private byte[] encP;
    private AlgorithmIdentifier digest;


    public McElieceCCA2PrivateKey(int n, int k, GF2mField field, PolynomialGF2mSmallM goppaPoly, Permutation p, AlgorithmIdentifier digest)
    {
        this.n = n;
        this.k = k;
        this.encField = field.getEncoded();
        this.encGp = goppaPoly.getEncoded();
        this.encP = p.getEncoded();
        this.digest = digest;
    }

    private McElieceCCA2PrivateKey(ASN1Sequence seq)
    {
        n = ((ASN1Integer)seq.getObjectAt(0)).intValueExact();

        k = ((ASN1Integer)seq.getObjectAt(1)).intValueExact();

        encField = ((ASN1OctetString)seq.getObjectAt(2)).getOctets();

        encGp = ((ASN1OctetString)seq.getObjectAt(3)).getOctets();

        encP = ((ASN1OctetString)seq.getObjectAt(4)).getOctets();

        digest = AlgorithmIdentifier.getInstance(seq.getObjectAt(5));
    }

    public int getN()
    {
        return n;
    }

    public int getK()
    {
        return k;
    }

    public GF2mField getField()
    {
        return new GF2mField(encField);
    }

    public PolynomialGF2mSmallM getGoppaPoly()
    {
        return new PolynomialGF2mSmallM(this.getField(), encGp);
    }

    public Permutation getP()
    {
        return new Permutation(encP);
    }

    public AlgorithmIdentifier getDigest()
    {
        return digest;
    }

    public ASN1Primitive toASN1Primitive()
    {

        ASN1EncodableVector v = new ASN1EncodableVector();

        // encode 
        v.add(new ASN1Integer(n));

        // encode 
        v.add(new ASN1Integer(k));

        // encode 
        v.add(new DEROctetString(encField));

        // encode 
        v.add(new DEROctetString(encGp));

        // encode 
        v.add(new DEROctetString(encP));

        v.add(digest);

        return new DERSequence(v);
    }

    public static McElieceCCA2PrivateKey getInstance(Object o)
    {
        if (o instanceof McElieceCCA2PrivateKey)
        {
            return (McElieceCCA2PrivateKey)o;
        }
        else if (o != null)
        {
            return new McElieceCCA2PrivateKey(ASN1Sequence.getInstance(o));
        }

        return null;
    }
}