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.DEROctetString;
import org.bouncycastle.asn1.cms.KEKIdentifier;
import org.bouncycastle.asn1.cms.KEKRecipientInfo;
import org.bouncycastle.asn1.cms.RecipientInfo;
import org.bouncycastle.operator.GenericKey;
import org.bouncycastle.operator.OperatorException;
import org.bouncycastle.operator.SymmetricKeyWrapper;

public abstract class KEKRecipientInfoGenerator
    implements RecipientInfoGenerator
{
    private final KEKIdentifier kekIdentifier;

    protected final SymmetricKeyWrapper wrapper;

    protected KEKRecipientInfoGenerator(KEKIdentifier kekIdentifier, SymmetricKeyWrapper wrapper)
    {
        this.kekIdentifier = kekIdentifier;
        this.wrapper = wrapper;
    }

    public final RecipientInfo generate(GenericKey contentEncryptionKey)
        throws CMSException
    {
        try
        {
            ASN1OctetString encryptedKey = new DEROctetString(wrapper.generateWrappedKey(contentEncryptionKey));

            return new RecipientInfo(new KEKRecipientInfo(kekIdentifier, wrapper.getAlgorithmIdentifier(), encryptedKey));
        }
        catch (OperatorException e)
        {
            throw new CMSException("exception wrapping content key: " + e.getMessage(), e);
        }
    }
}