CMSSignedDataGenerator gen = new CMSSignedDataGenerator();
gen.addSigner(_origKP.getPrivate(), _origCert, CMSSignedDataGenerator.DIGEST_SHA1);
gen.addCertificatesAndCRLs(certs);
X509AttributeCertificate attrCert = CMSTestUtil.getAttributeCertificate();
X509Store store = X509Store.getInstance("AttributeCertificate/Collection",
new X509CollectionStoreParameters(Collections.singleton(attrCert)), "BC");