Session session = Session.getDefaultInstance(props, null);
MimeMessage msg = new MimeMessage(session, new FileInputStream("encrypted.message"));
SMIMEEnveloped m = new SMIMEEnveloped(msg);
RecipientInformationStore recipients = m.getRecipientInfos();
RecipientInformation recipient = recipients.get(recId);
MimeBodyPart res = SMIMEUtil.toMimeBodyPart(recipient.getContent(ks.getKey(keyAlias, null), "BC"));
System.out.println("Message Contents");