http://www.bouncycastle.org/java.html: The Bouncy Castle Java APIs for CMS, PKCS, EAC, TSP, CMP, CRMF, OCSP, and certificate generation. This jar contains APIs for JDK 1.5 to JDK 1.8. The APIs can be used in conjunction with a JCE/JCA provider such as the one provided with the Bouncy Castle Cryptography APIs.
  • The Legion of the Bouncy Castle Inc. 
package org.bouncycastle.cms.bc;

import org.bouncycastle.cert.X509CertificateHolder;
import org.bouncycastle.cms.CMSSignatureAlgorithmNameGenerator;
import org.bouncycastle.cms.SignerInformationVerifier;
import org.bouncycastle.crypto.params.AsymmetricKeyParameter;
import org.bouncycastle.operator.DigestAlgorithmIdentifierFinder;
import org.bouncycastle.operator.DigestCalculatorProvider;
import org.bouncycastle.operator.OperatorCreationException;
import org.bouncycastle.operator.SignatureAlgorithmIdentifierFinder;
import org.bouncycastle.operator.bc.BcRSAContentVerifierProviderBuilder;

public class BcRSASignerInfoVerifierBuilder
{
    private BcRSAContentVerifierProviderBuilder contentVerifierProviderBuilder;
    private DigestCalculatorProvider digestCalculatorProvider;
    private CMSSignatureAlgorithmNameGenerator sigAlgNameGen;
    private SignatureAlgorithmIdentifierFinder sigAlgIdFinder;

    public BcRSASignerInfoVerifierBuilder(CMSSignatureAlgorithmNameGenerator sigAlgNameGen, SignatureAlgorithmIdentifierFinder sigAlgIdFinder, DigestAlgorithmIdentifierFinder digestAlgorithmFinder, DigestCalculatorProvider digestCalculatorProvider)
    {
        this.sigAlgNameGen = sigAlgNameGen;
        this.sigAlgIdFinder = sigAlgIdFinder;
        this.contentVerifierProviderBuilder = new BcRSAContentVerifierProviderBuilder(digestAlgorithmFinder);
        this.digestCalculatorProvider = digestCalculatorProvider;
    }

    public SignerInformationVerifier build(X509CertificateHolder certHolder)
        throws OperatorCreationException
    {
        return new SignerInformationVerifier(sigAlgNameGen, sigAlgIdFinder, contentVerifierProviderBuilder.build(certHolder), digestCalculatorProvider);
    }

    public SignerInformationVerifier build(AsymmetricKeyParameter pubKey)
        throws OperatorCreationException
    {
        return new SignerInformationVerifier(sigAlgNameGen, sigAlgIdFinder, contentVerifierProviderBuilder.build(pubKey), digestCalculatorProvider);
    }
}