AlgorithmIdentifier digAlgId = new DefaultDigestAlgorithmIdentifierFinder().find(sigAlgId);
BcRSAContentSignerBuilder sigBuild = new BcRSAContentSignerBuilder(sigAlgId, digAlgId);
ContentSigner signer;
try {
signer = sigBuild.build(BouncyCastleHelpers.toAsymmetricKeyParameter(keyPair.getPrivate()));
} catch (OperatorCreationException e) {
throw new IllegalArgumentException("Error building content signer", e);
}
PKCS10CertificationRequest csrHolder = csrBuilder.build(signer);