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.DEROctetString;
import org.bouncycastle.asn1.cms.IssuerAndSerialNumber;
import org.bouncycastle.asn1.cms.KeyTransRecipientInfo;
import org.bouncycastle.asn1.cms.RecipientIdentifier;
import org.bouncycastle.asn1.cms.RecipientInfo;
import org.bouncycastle.operator.AsymmetricKeyWrapper;
import org.bouncycastle.operator.GenericKey;
import org.bouncycastle.operator.OperatorException;

public abstract class KeyTransRecipientInfoGenerator
    implements RecipientInfoGenerator
{
    protected final AsymmetricKeyWrapper wrapper;

    private IssuerAndSerialNumber issuerAndSerial;
    private byte[] subjectKeyIdentifier;

    protected KeyTransRecipientInfoGenerator(IssuerAndSerialNumber issuerAndSerial, AsymmetricKeyWrapper wrapper)
    {
        this.issuerAndSerial = issuerAndSerial;
        this.wrapper = wrapper;
    }

    protected KeyTransRecipientInfoGenerator(byte[] subjectKeyIdentifier, AsymmetricKeyWrapper wrapper)
    {
        this.subjectKeyIdentifier = subjectKeyIdentifier;
        this.wrapper = wrapper;
    }

    public final RecipientInfo generate(GenericKey contentEncryptionKey)
        throws CMSException
    {
        byte[] encryptedKeyBytes;
        try
        {
            encryptedKeyBytes = wrapper.generateWrappedKey(contentEncryptionKey);
        }
        catch (OperatorException e)
        {
            throw new CMSException("exception wrapping content key: " + e.getMessage(), e);
        }

        RecipientIdentifier recipId;
        if (issuerAndSerial != null)
        {
            recipId = new RecipientIdentifier(issuerAndSerial);
        }
        else
        {
            recipId = new RecipientIdentifier(new DEROctetString(subjectKeyIdentifier));
        }

        return new RecipientInfo(new KeyTransRecipientInfo(recipId, wrapper.getAlgorithmIdentifier(),
            new DEROctetString(encryptedKeyBytes)));
    }
}