http://www.bouncycastle.org/java.html: The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5 to JDK 1.7. 
package org.bouncycastle.asn1.pkcs;

import org.bouncycastle.asn1.ASN1Encodable;
import org.bouncycastle.asn1.ASN1EncodableVector;
import org.bouncycastle.asn1.ASN1Sequence;
import org.bouncycastle.asn1.DERObject;
import org.bouncycastle.asn1.DERObjectIdentifier;
import org.bouncycastle.asn1.DERSequence;
import org.bouncycastle.asn1.DERTaggedObject;

public class CertBag
    extends ASN1Encodable
{
    ASN1Sequence        seq;
    DERObjectIdentifier certId;
    DERObject           certValue;

    public CertBag(
        ASN1Sequence    seq)
    {
        this.seq = seq;
        this.certId = (DERObjectIdentifier)seq.getObjectAt(0);
        this.certValue = ((DERTaggedObject)seq.getObjectAt(1)).getObject();
    }

    public CertBag(
        DERObjectIdentifier certId,
        DERObject           certValue)
    {
        this.certId = certId;
        this.certValue = certValue;
    }

    public DERObjectIdentifier getCertId()
    {
        return certId;
    }

    public DERObject getCertValue()
    {
        return certValue;
    }

    public DERObject toASN1Object()
    {
        ASN1EncodableVector  v = new ASN1EncodableVector();

        v.add(certId);
        v.add(new DERTaggedObject(0, certValue));

        return new DERSequence(v);
    }
}