// request
//create a nonce to avoid replay attack
BigInteger nonce = BigInteger.valueOf(nonceTimeinMillis);
DEROctetString nonceDer = new DEROctetString(nonce.toByteArray());
Extension ext = new Extension(OCSPObjectIdentifiers.id_pkix_ocsp_nonce, true, nonceDer);
Extensions exts = new Extensions(ext);
OCSPReqBuilder ocspReqBuilder = new OCSPReqBuilder();
ocspReqBuilder.addRequest(certId);
ocspReqBuilder.setRequestExtensions(exts);