http://www.bouncycastle.org/java.html: The Bouncy Castle Java APIs for CMS, PKCS, EAC, TSP, CMP, CRMF, OCSP, and certificate generation. This jar contains APIs for JDK 1.5 to JDK 1.8. The APIs can be used in conjunction with a JCE/JCA provider such as the one provided with the Bouncy Castle Cryptography APIs.
  • The Legion of the Bouncy Castle Inc. 
package org.bouncycastle.cms;

import org.bouncycastle.asn1.ASN1OctetString;
import org.bouncycastle.asn1.cms.IssuerAndSerialNumber;
import org.bouncycastle.asn1.cms.KeyTransRecipientInfo;
import org.bouncycastle.asn1.cms.RecipientIdentifier;
import org.bouncycastle.asn1.x509.AlgorithmIdentifier;


the KeyTransRecipientInformation class for a recipient who has been sent a secret
key encrypted using their public key that needs to be used to
extract the message.

/**
 * the KeyTransRecipientInformation class for a recipient who has been sent a secret
 * key encrypted using their public key that needs to be used to
 * extract the message.
 */
public class KeyTransRecipientInformation
    extends RecipientInformation
{
    private KeyTransRecipientInfo info;

    KeyTransRecipientInformation(
        KeyTransRecipientInfo   info,
        AlgorithmIdentifier     messageAlgorithm,
        CMSSecureReadable       secureReadable,
        AuthAttributesProvider  additionalData)
    {
        super(info.getKeyEncryptionAlgorithm(), messageAlgorithm, secureReadable, additionalData);

        this.info = info;

        RecipientIdentifier r = info.getRecipientIdentifier();

        if (r.isTagged())
        {
            ASN1OctetString octs = ASN1OctetString.getInstance(r.getId());

            rid = new KeyTransRecipientId(octs.getOctets());
        }
        else
        {
            IssuerAndSerialNumber   iAnds = IssuerAndSerialNumber.getInstance(r.getId());

            rid = new KeyTransRecipientId(iAnds.getName(), iAnds.getSerialNumber().getValue());
        }
    }

    protected RecipientOperator getRecipientOperator(Recipient recipient)
        throws CMSException
    {
        return ((KeyTransRecipient)recipient).getRecipientOperator(keyEncAlg, messageAlgorithm, info.getEncryptedKey().getOctets());
    }
}