BigInteger serialNumber = BigInteger.valueOf((startDate.getTimeInMillis()));
X500Name issuer = new X500Name(IETFUtils.rDNsFromString(issuerDirString, RFC4519Style.INSTANCE));
JcaX509v3CertificateBuilder certGen = new JcaX509v3CertificateBuilder(issuer, serialNumber, startDate.getTime(), endDate.getTime(), issuer, kp.getPublic());
JcaX509ExtensionUtils extensionUtils = new JcaX509ExtensionUtils();
certGen.addExtension(Extension.subjectKeyIdentifier, false, extensionUtils.createSubjectKeyIdentifier(kp.getPublic()));
certGen.addExtension(Extension.basicConstraints, false, new BasicConstraints(isCertAuthority));
certGen.addExtension(Extension.authorityKeyIdentifier, false, extensionUtils.createAuthorityKeyIdentifier(signerPublicKey));
if (isCertAuthority) {
certGen.addExtension(Extension.keyUsage, true, new KeyUsage(KeyUsage.keyCertSign));
}
X509CertificateHolder cert = certGen.build(new JcaContentSignerBuilder(signingAlgorithm).build(signerPrivateKey));