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.operator.bc;

import java.io.IOException;

import org.bouncycastle.asn1.x509.AlgorithmIdentifier;
import org.bouncycastle.asn1.x509.SubjectPublicKeyInfo;
import org.bouncycastle.crypto.Digest;
import org.bouncycastle.crypto.Signer;
import org.bouncycastle.crypto.params.AsymmetricKeyParameter;
import org.bouncycastle.crypto.signers.DSADigestSigner;
import org.bouncycastle.crypto.signers.ECDSASigner;
import org.bouncycastle.crypto.util.PublicKeyFactory;
import org.bouncycastle.operator.DigestAlgorithmIdentifierFinder;
import org.bouncycastle.operator.OperatorCreationException;

public class BcECContentVerifierProviderBuilder
    extends BcContentVerifierProviderBuilder
{
    private DigestAlgorithmIdentifierFinder digestAlgorithmFinder;

    public BcECContentVerifierProviderBuilder(DigestAlgorithmIdentifierFinder digestAlgorithmFinder)
    {
        this.digestAlgorithmFinder = digestAlgorithmFinder;
    }

    protected Signer createSigner(AlgorithmIdentifier sigAlgId)
        throws OperatorCreationException
    {
        AlgorithmIdentifier digAlg = digestAlgorithmFinder.find(sigAlgId);
        Digest dig = digestProvider.get(digAlg);

        return new DSADigestSigner(new ECDSASigner(), dig);
    }

    protected AsymmetricKeyParameter extractKeyParameters(SubjectPublicKeyInfo publicKeyInfo)
        throws IOException
    {
        return PublicKeyFactory.createKey(publicKeyInfo);
    }
}